crane

Abstract

To provide a crane capable of more stably winding up an attachment when driving multiple winches simultaneously.SOLUTION: A crane comprises a first winch (6), a first hydraulic motor (31) to drive the first winch, a second winch (7), a second hydraulic motor (131) arranged downstream or upstream of the first hydraulic motor to drive the second winch, and a first hydraulic pump (30), a second hydraulic pump (130), and attachment (16). The crane performs a special control to stop the pressure oil supply to the second hydraulic motor by the first hydraulic pump and to stop the pressure oil supply to the first hydraulic motor by the second hydraulic pump when at least one of the pressure between the first hydraulic motor and the first hydraulic pump and of the pressure between the second hydraulic motor and the second hydraulic pump exceeds a prescribed value during winding up of the first winch and of the second winch.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a crane. [Background technology]

[0002] To drive multiple actuators simultaneously at high speed, cranes often have a series circuit (hydraulic circuit) in which each hydraulic motor driving a winch is connected in series to a hydraulic pump, and pressure oil discharged from the hydraulic pump is sequentially supplied from the upstream hydraulic motor to the downstream hydraulic motor. Another known configuration involves a confluence circuit that combines pressure oil supplied from one hydraulic pump with pressure oil supplied from another hydraulic pump for a single hydraulic motor, enabling each hydraulic motor to be driven at higher speeds. In this type of crane hydraulic circuit, if the discharge pressure of the hydraulic motor exceeds a set pressure, the hydraulic motor is controlled to a large tilt position to suppress the discharge pressure of the hydraulic motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4291110 Summary of the Invention [Problem to be solved by the invention]

[0004] Crane operations often involve simultaneously driving multiple winches to operate attachments, such as driving two winches simultaneously to operate a bucket for excavation work. When lifting an attachment such as a bucket, a high load is placed on the two winches. If the winches continue to operate under a high load and the circuit pressure in the series circuit exceeds the relief pressure, the pressurized oil in the circuit is returned to the tank via the relief valve. This can result in an insufficient supply of pressurized oil to the hydraulic motor, causing the winch to stop operating and making it impossible to lift the bucket.

[0005] The present invention has been devised with the object of providing a crane that can hoist an attachment more stably when multiple winches are driven simultaneously. [Means for solving the problem]

[0006] In order to achieve the above object, a representative aspect of the present invention is a hydraulic lifting device including a first winch, a first hydraulic motor for driving the first winch, a second winch, and a hydraulic motor for driving the second winch. In the flow of pressure oil a first hydraulic pump that supplies pressurized oil to the first hydraulic motor and the second hydraulic motor; a second hydraulic pump that supplies pressurized oil to the first hydraulic motor and the second hydraulic motor; and an attachment operated by the first winch and the second winch, wherein when the first winch and the second winch are performing a hoisting operation and at least one of the pressure between the first hydraulic motor and the first hydraulic pump and the pressure between the second hydraulic motor and the second hydraulic pump is equal to or higher than a predetermined value, special control is performed to stop the supply of pressurized oil to the second hydraulic motor by the first hydraulic pump and the supply of pressurized oil to the first hydraulic motor by the second hydraulic pump.

[0007] According to the present invention, when a plurality of winches are driven simultaneously, attachments such as buckets can be stably hoisted up. Note that problems, configurations, and effects other than those described above will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of a crane according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing the overall configuration of a hydraulic circuit of a crane. [Figure 3] FIG. 1 is an overall configuration diagram (hydraulic circuit diagram) of a drive device for a main hoisting winch. [Figure 4]10 is a flowchart showing a processing procedure for drive control of a main winch and an auxiliary winch. [Figure 5] 5 is a flowchart showing a processing procedure for merging prohibition control shown in FIG. 4. [Figure 6] 10 is a flowchart showing a processing procedure for merging prohibition control according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a crane according to the present invention will be described with reference to the drawings.

[0010] Figure 1 is a side view of a crane according to an embodiment of the present invention. The crane 1 shown in Figure 1 is a crawler crane and includes a running body 2, a rotating body 4 rotatably mounted on the running body 2 via a rotating device 3, a boom 5 attached to the tip of the rotating body 4 so that it can be raised and lowered, and sheaves 10, 11 and sheaves 17, 18 provided at the tip of the boom 5. A bucket 16, which is an example of an attachment, is suspended by a main hoisting rope 12 that passes through sheaves 10 and 17, and an auxiliary hoisting rope 13 that passes through sheaves 11 and 18.

[0011] The rotating body 4 is provided with a cab 9, and the operator operates control levers 25, 26 (described later) in the cab 9 to perform lifting and excavation work with the crane 1. Incidentally, the control levers 25, 26 are in a neutral position when not in operation, and can be operated in two speed stages: low speed and high speed. The operator can then tilt the control levers 25, 26 in a specified direction to perform the desired operation.

[0012] The main hoisting rope 12 and the auxiliary hoisting rope 13 are wound around a main hoisting winch (first winch) 6 and an auxiliary hoisting winch (second winch) 7 mounted on the rotating body 4, respectively, and the ropes 12 and 13 are wound up or let out by driving the winches 6 and 7, thereby raising or lowering the load. The bucket 16 is suspended by the main hoisting rope 12 and the auxiliary hoisting rope 13, and the main hoisting winch 6 and the auxiliary hoisting winch 7 are driven simultaneously, allowing the bucket 16 to be hoisted up or down. As will be described in more detail later, in order to stably hoist the bucket 16, a merger prohibition control (special control) is performed in which the main hoisting winch 6 and the auxiliary hoisting winch 7 are driven by separate hydraulic pumps 30 and 130 (see Figure 2).

[0013] A pendant rope 14 is connected to the tip of the boom 5, and when the boom hoisting rope 15 is wound or unwound by driving the boom hoisting winch 8 mounted on the rotating body 4, the boom 5 is raised or lowered via the pendant rope 14.

[0014] FIG. 2 is a schematic diagram showing the overall configuration of the hydraulic circuit of the crane 1. As shown in FIG. 2, the crane 1 is equipped with a hydraulic motor (first hydraulic motor) 31 that drives the main hoisting winch 6, a hydraulic motor (second hydraulic motor) 131 that drives the auxiliary hoisting winch 7, a hydraulic motor 231 that drives the hoisting winch 8, hydraulic motors 331, 431 for traveling, and a swing motor (not shown). Each of the hydraulic motors 31, 131, 231, 331, 431 is driven by pressure oil supplied from a hydraulic pump 30 (first hydraulic pump) and / or a hydraulic pump 130 (second hydraulic pump). Both the hydraulic pumps 30, 130 are variable displacement pumps, such as swash plate piston pumps. The hydraulic motors 31, 131, 231, 331, 431 are also variable displacement motors.

[0015] The hydraulic motors 31, 131, 431 are connected in series to the hydraulic pump 30 to form a series circuit S1. Specifically, in order from the upstream side of the hydraulic pump 30 in the flow of pressure oil, the hydraulic motor 431 for traveling, the hydraulic motor 131 for the auxiliary winch 7, and the hydraulic motor 31 for the main winch 6 are arranged in series on the center pipe L1 via directional control valves 432, 132-1, 32, respectively.

[0016] The pressure oil discharged from the hydraulic pump 30 flows through the center pipe L1 and first flows into the hydraulic motor 431. The pressure oil flowing out from the hydraulic motor 431 then flows into the hydraulic motor 131. The pressure oil flowing out from the hydraulic motor 131 then flows into the hydraulic motor 31, and the pressure oil flowing out from the hydraulic motor 31 returns to the tank 34. In this way, the series circuit S1 allows the single hydraulic pump 30 to supply pressure oil to the hydraulic motors 431, 131, and 31 in sequence, thereby driving the three hydraulic motors.

[0017] Similarly, the hydraulic motors 31, 131, 231, 331 are connected in series to the hydraulic pump 130 to form a series circuit S2. Specifically, from the upstream side of the hydraulic pump 130 in the flow of pressure oil, the hydraulic motor 331 for traveling, the hydraulic motor 231 for the hoisting winch 8, the hydraulic motor 131 for the auxiliary winch 7, and the hydraulic motor 31 for the main hoisting winch 6 are arranged in series on the center pipe L2 via directional control valves 332, 232, 132, 32-1, respectively.

[0018] The pressure oil discharged from the hydraulic pump 130 flows through the center pipe L2 and first flows into the hydraulic motor 331. The pressure oil that flows out from the hydraulic motor 331 then flows into the hydraulic motor 231. The pressure oil that flows out from the hydraulic motor 231 then flows into the hydraulic motor 131. The pressure oil that flows out from the hydraulic motor 131 then flows into the hydraulic motor 31. The pressure oil that flows out from the hydraulic motor 31 returns to the tank 34. In this way, the series circuit S2 can drive four hydraulic motors by supplying pressure oil to the hydraulic motors 331, 231, 131, and 31 in sequence using one hydraulic pump 130.

[0019] In FIG. 2, the hydraulic motor 131 for the auxiliary winch 7 is provided upstream of the hydraulic motor 31 for the main winch 6 relative to the hydraulic pump 30 and the hydraulic pump 130, but the positions of the two may be reversed.

[0020] Furthermore, in this embodiment, there are provided junction circuits M1 and M2 that join the series circuits S1 and S2.

[0021] The confluence circuit M1 is a circuit for merging pressure oil from the hydraulic pump 130 into main pipelines 37, 38 that supply pressure oil from the hydraulic pump 30 to the hydraulic motor 31, and includes pipelines 71, 72. The pipeline 71 is connected to the main pipeline 37, and the pipeline 72 is connected to the main pipeline 38, so that pressure oil from the hydraulic pump 130 can be supplied to the hydraulic motor 31 via the pipelines 71, 72. Therefore, the hydraulic motor 31 can be driven by the two hydraulic pumps 30, 130.

[0022] The confluence circuit M2 is a circuit for merging the pressure oil from the hydraulic pump 30 into main pipelines 137, 138 that supply pressure oil from the hydraulic pump 30 to the hydraulic motor 131, and includes pipelines 171, 172. The pipeline 171 is connected to the main pipeline 137, and the pipeline 172 is connected to the main pipeline 138, so that the pressure oil from the hydraulic pump 30 can be supplied to the hydraulic motor 131 via the pipelines 171, 172. Therefore, the hydraulic motor 131 can be driven by the two hydraulic pumps 30, 130.

[0023] Furthermore, in the series circuit S1, a relief valve 35 is provided between the hydraulic pump 30 and the directional control valve 432 to limit the pressure within the circuit. Furthermore, a pressure detector 65 for detecting the pressure within the circuit is provided in the center pipe L1 between the hydraulic pump 30 and the directional control valve 432. Pressure data detected by the pressure detector 65 is input to the controller 60 (see FIG. 3). Similarly, the series circuit S2 is provided with a relief valve 36 and a pressure detector 66. The pressure detector 65 may be located anywhere as long as it can appropriately detect the circuit pressure of the series circuit S1. For example, it may detect the pressure inside the hydraulic pump 30, or it may detect the pressure inside the hydraulic motors 31, 131. The pressure detector 66 may also be located anywhere as long as it can appropriately detect the circuit pressure of the series circuit S2.

[0024] Next, the details of the configuration of the hydraulic circuit between the hydraulic motor and the directional control valve will be described using the hydraulic circuit of the hydraulic motor 31 that drives the main hoisting winch 6 as an example.

[0025] Figure 3 is an overall configuration diagram (hydraulic circuit diagram) of the drive device for the main hoisting winch 6. As shown in Figure 3, the drive device for the main hoisting winch 6 includes a variable displacement hydraulic pump 30, a variable displacement hydraulic motor (first hydraulic motor) 31 driven by pressurized oil from the hydraulic pump 30 supplied via a pair of main pipelines 37, 38, a directional control valve 32 that controls the flow of pressurized oil from the hydraulic pump 30 to the hydraulic motor 31, a counterbalance valve 33 interposed between the directional control valve 32 and the hydraulic motor 31, a relief valve 35 (see Figure 2) that limits the pump discharge pressure, an electric operation lever 25 that issues a command to drive the main hoisting winch 6, and a motor capacity control device 40 that controls the motor capacity (also referred to as motor displacement or motor absorption amount) of the hydraulic motor 31.

[0026] The output shaft of the hydraulic motor 31 is connected to the drum 6a of the main hoisting winch 6, and the drum 6a rotates in conjunction with the rotation of the hydraulic motor 31, thereby winding or unwinding the main hoisting rope 12. The hydraulic pump 30 is driven by an engine (not shown) provided inside the revolving unit 4. The pump capacity of the hydraulic pump 30 is controlled in accordance with the pump discharge pressure by so-called horsepower control, and the motor capacity of the hydraulic motor 31 is also controlled by horsepower control in a similar manner.

[0027] An operation signal from the operating lever 25 is input to the solenoid directional control valves 55, 56 via the controller 60. The solenoid directional control valves 55, 56 are normally in position P1. When the operator operates the operating lever 25, an operation signal is input from the controller 60 to the solenoid directional control valves 55, 56, and the solenoid directional control valves 55, 56 switch from position P1 to position P2. This causes pressure oil (pilot pressure) from the pilot pump 47, which serves as a hydraulic source, to be introduced into the pressure-receiving portion 32a or 32b of the directional control valve 32, switching the directional control valve 32 from position A0 to position A1 or position A2. When the directional control valve 32 switches to position A1, the main hoisting winch 6 is hoisted up, and when the directional control valve 32 switches to position A2, the main hoisting winch 6 is lowered. In FIG. 3, symbols E1 to E5 indicate electrical wiring.

[0028] Here, a hydraulic operating lever may be used instead of the electric operating lever 25. In this case, pilot pressure from a hydraulic source may be introduced directly to the pressure receiving portions 32a, 32b of the directional control valve 32 by operating the hydraulic operating lever. Also, an electromagnetic proportional directional control valve may be used instead of the directional control valve 32. In this case, there is no need to introduce pilot pressure to the directional control valve, which simplifies the hydraulic piping.

[0029] The hoisting speed and lowering speed of the main hoisting winch 6 are controlled by a motor capacity control device 40. The motor capacity control device 40 is a device for changing the motor displacement of the hydraulic motor 31, and is specifically configured as follows.

[0030] The hydraulic motor 31 is provided with a piston 41 that changes the angle of the swash plate (motor tilt). Pressurized oil from the main pipe 38 is introduced into one oil chamber 41a of the piston 41, and pressurized oil from the main pipe 38 is introduced into the other oil chamber 41b via a load pressure control spool 42, which is a control valve, a tilt control spool 44, which is also a control valve, and a throttle 50. The diameter of the piston in the oil chamber 41b is larger than the diameter of the piston in the oil chamber 41a.

[0031] Therefore, the piston 41 moves in direction a or direction b depending on the magnitude relationship between value X, which is the pressure of the pressurized oil introduced into oil chamber 41a multiplied by the cross-sectional area of ​​the piston, and value Y, which is the pressure of the pressurized oil introduced into oil chamber 41b multiplied by the cross-sectional area of ​​the piston. Specifically, when value X is greater than value Y, the piston 41 moves in direction a, and the motor displacement increases. As a result, the rotational speed of the hydraulic motor 31 decreases (becomes slower). On the other hand, when value X is less than value Y, the piston 41 moves in direction b, and the motor displacement decreases. As a result, the rotational speed of the hydraulic motor 31 increases (becomes faster).

[0032] The load pressure control spool 42 includes a piston 43. One oil chamber 43a of the piston 43 receives pressurized oil from the main line 38, and the other oil chamber 43b receives pressurized oil from the main line 37. The load pressure control spool 42 switches from position B0 to position B1 or B2 depending on the balance between the difference in force acting on oil chamber 43a and the force acting on oil chamber 43b and the biasing force of spring 42a.

[0033] The tilt control spool 44 is equipped with a piston 45. Pressurized oil (pilot pressure) from a fixed displacement pilot pump 47 is introduced into an oil chamber 45a of the piston 45 via an electromagnetic proportional valve 46. The pilot pump 47 is driven by an engine (not shown). The opening of the electromagnetic proportional valve 46 is controlled in response to a control signal from a controller 60. The tilt control spool 44 switches from position C0 to position C1 or C2 depending on the balance between the force acting on the oil chamber 45a and the biasing force of the spring 44a.

[0034] When the load pressure control spool 42 is switched to position B1 and the tilt control spool 44 is switched to position C1, pressure oil from the main conduit 38 flows through the conduit 51 and is introduced into the oil chamber 41b. Note that a throttle 50 is provided in the conduit 51, which limits the flow rate of pressure oil to prevent a sudden increase in the flow rate of pressure oil from being supplied to the oil chamber 41b.

[0035] On the other hand, when the tilt control spool 44 switches to position C2, the oil chamber 41b and the tank 34 communicate with each other, and the pressure oil in the oil chamber 41b returns to the tank 34.

[0036] When the load pressure control spool 42 is switched to position B0 and the tilt control spool 44 is switched to position C0, the motor tilt becomes stable.

[0037] Although not shown, the hydraulic motor 131 for the auxiliary winch 7 also has a circuit configuration similar to that described above, and by operating the control lever 26, the hydraulic motor (second hydraulic motor) 131 of the auxiliary winch 7 rotates, and the motor displacement of the hydraulic motor 131 is controlled by a motor capacity control device 140 for the hydraulic motor 131 of the auxiliary winch 7. By simultaneously operating the control levers 25 and 26, the bucket 16 can be hoisted up or down, allowing excavation work to be performed. The other hydraulic motors 231, 331, 431 are also driven by roughly the same configuration, but because this is known, a description thereof will be omitted here.

[0038] Next, the operation of the hydraulic circuit of the crane 1 shown in FIG. 2 will be described.

[0039] (Slow winding operation) When the operator operates the main hoisting winch 6 by placing the operating lever 25 for the main hoisting winch 6 at low speed (first position), the directional control valve 32 (for low speed) switches from position A0 to position A1. Then, pressure oil discharged from the hydraulic pump 30 flows through the main pipe 38 and into the hydraulic motor 31, causing the hydraulic motor 31 to rotate at low speed. Pressure oil flowing out from the hydraulic motor 31 flows through the main pipe 37 and is ultimately returned to the tank 34. In this way, the main hoisting winch 6 hoists the main hoisting rope 12 at low speed.

[0040] When the operator operates the auxiliary winch 7 by placing the operating lever 26 for the auxiliary winch 7 at low speed (first position), the directional control valve 132 switches from position A20 to position A21. Then, pressure oil discharged from the hydraulic pump 130 flows through the main pipe 138 into the hydraulic motor 131, causing the hydraulic motor 131 to rotate at low speed. The pressure oil flowing out of the hydraulic motor 131 flows through the main pipe 137 and is ultimately returned to the tank 34. In this way, the auxiliary winch 7 winds up the auxiliary hoisting rope 13 at low speed.

[0041] In this way, when the main winch 6 and the auxiliary winch 7 are operated to hoist at low speed, the main winch 6 is driven only by pressurized oil from the hydraulic pump 30, and the hydraulic motor 131 for the auxiliary winch 7 is driven only by pressurized oil from the hydraulic pump 130.

[0042] When the operator operates the control lever for the hoisting winch 8 or the control lever for traveling, the corresponding directional control valves 232, 332, 432 are switched to their respective predetermined positions. Then, pressure oil from the hydraulic pump 30 is supplied to the hydraulic motor 431 for traveling, and pressure oil from the hydraulic pump 130 is supplied to the hydraulic motor 231 for the hoisting winch 8 and the hydraulic motor 331 for traveling, causing the hydraulic motors 231, 331, 431 to rotate, respectively.

[0043] (High-speed winding operation) When the operator operates the operation lever 25 for the main hoisting winch 6 at high speed (second position) to perform a hoisting operation, the directional control valve 32 switches from position A0 to position A1, and the directional control valve 32-1 (for high speed) switches from position A10 to position A11. Then, pressure oil discharged from the hydraulic pump 30 flows through the main pipe 38 and into the hydraulic motor 31. Furthermore, pressure oil discharged from the hydraulic pump 130 flows through the pipe 72 of the junction circuit M1, joins the main pipe 38, and flows into the hydraulic motor 31.

[0044] In other words, the pressure oil discharged from the hydraulic pump 30 and the pressure oil discharged from the hydraulic pump 130 flow into the hydraulic motor 31 at a flow rate that is approximately twice as high as that at low speed, causing the hydraulic motor 31 to rotate at high speed. The pressure oil flowing out from the hydraulic motor 31 flows through the main pipe 37 and the pipe 71 of the junction circuit M1, and is finally returned to the tank 34. In this way, the main hoisting winch 6 reels in the main hoisting rope 12 at high speed.

[0045] When the operator operates the operation lever 26 for the auxiliary winch 7 at high speed (second position) to perform a hoisting operation, the directional control valve 132 switches from position A20 to position A21, and the directional control valve 132-1 (for high speed) switches from position A30 to position A31. Then, pressure oil discharged from the hydraulic pump 130 flows through the main pipe 138 and into the hydraulic motor 131. Further, pressure oil discharged from the hydraulic pump 130 flows through the pipe 172 of the junction circuit M2, joins the main pipe 138, and flows into the hydraulic motor 131.

[0046] In other words, the pressure oil discharged from the hydraulic pump 130 and the pressure oil discharged from the hydraulic pump 30 flow into the hydraulic motor 131 at a flow rate that is approximately twice as high as that at low speed, causing the hydraulic motor 131 to rotate at high speed. The pressure oil flowing out from the hydraulic motor 131 flows through the main pipe 137 and the pipe 171 of the junction circuit M2, and is finally returned to the tank 34. In this way, the auxiliary hoisting winch 7 reel in the auxiliary hoisting rope 13 at high speed.

[0047] In this way, when the main winch 6 and the auxiliary winch 7 are simultaneously operated to hoist at high speed, the main winch 6 and the auxiliary winch 7 are driven by pressure oil from both the hydraulic pump 30 and the hydraulic pump 130, respectively.

[0048] In this embodiment, when the main hoisting winch 6 and auxiliary hoisting winch 7 are driven simultaneously to perform high-speed hoisting operation with the bucket 16 suspended by the main hoisting rope 12 and auxiliary hoisting rope 13, if the circuit pressure in at least one of the series circuits S1 and S2 reaches a predetermined value or higher, pressure oil merging prohibition control (special control) is performed to prevent the circuit pressure from reaching the relief pressure, allowing the bucket 16 to be hoisted. Details of the pressure oil merging prohibition control in this embodiment will be described below.

[0049] FIG. 4 is a flowchart showing the processing procedure for controlling the drive of the main winch 6 and the auxiliary winch 7.

[0050] The controller 60 is configured to include an arithmetic processing unit having a CPU, memory devices such as ROM and RAM, and other peripheral circuits. The controller 60 is connected to the operation levers 25 and 26 via electrical wiring E1, and is also electrically connected to pressure detectors 65 and 66 via electrical wiring E2 (see FIG. 3). Based on detection signals input from these devices, the controller 60 controls the operation of the solenoid switching valves 55 and 56, or the operation of the solenoid proportional valve 46.

[0051] First, the controller 60 determines whether the operating lever 25 of the main hoisting winch 6 is in a hoisting operation (step S1). If the operating lever 25 is in a hoisting operation (step S1 / Yes), the controller 60 determines whether the operating lever 26 of the auxiliary hoisting winch 7 is in a hoisting operation (step S2). If the operating lever 26 is in a hoisting operation (step S2 / Yes), the controller 60 determines that the main hoisting winch 6 and the auxiliary hoisting winch 7 are simultaneously in a hoisting operation, and monitors the circuit pressure P of the series circuits S1, S2 (step S3). If at least one of the pressures (circuit pressure P) detected by the pressure detector 65 and the pressure detector 66 is equal to or greater than a predetermined value (Pr) (step S3 / Yes), the controller 60 executes merger prohibition control (step S4).

[0052] In this embodiment, the "predetermined value Pr" is a value smaller than the set pressure of the relief valves 35, 36, and is set in advance to a value of, for example, about 80% to 90% of the set pressure.

[0053] In addition, if at least one of the operating levers 25 and 26 is not operated (step S1 / No, step S2 / No), or if the circuit pressure P is less than the predetermined value Pr (step S3 / No), the merging prohibition control described below is not performed.

[0054] FIG. 5 is a flowchart showing the processing procedure of the merging prohibition control shown in FIG.

[0055] As shown in FIG. 5, when the merger prohibition control is initiated, the controller 60 switches the high-speed directional control valve 32-1 of the main hoisting winch 6 to its initial position (position A10) (step S41). That is, the supply of pressure oil from the hydraulic pump 130 to the hydraulic motor 31 is stopped. Next, the controller 60 switches the high-speed directional control valve 132-1 of the auxiliary hoisting winch 7 to its initial position (position A30) (step S42). That is, the supply of pressure oil from the hydraulic pump 30 to the hydraulic motor 131 is stopped. Next, the controller 60 determines whether the operating levers 25, 26 are performing a hoisting operation (step S43), and maintains the jog prohibition control until the hoisting operation is stopped (until a "No" is determined in step S43). That is, the directional control valves 32-1, 132-1 are held in their initial positions until the operating levers 25, 26 are in their neutral positions.

[0056] In this way, since the directional control valve 32-1 is held at position A10 and the directional control valve 132-1 is held at position A30, the hydraulic motor 31 for the main hoisting winch 6 is driven only by pressure oil from the hydraulic pump 30, and the hydraulic motor 131 for the auxiliary hoisting winch 7 is driven only by pressure oil from the hydraulic pump 130. In other words, during merger prohibition control, the series circuit S1 becomes a circuit for driving the main hoisting winch 6, and the series circuit S2 becomes a circuit for driving the auxiliary hoisting winch 7.

[0057] As described above, according to the first embodiment, when the circuit pressure P of the series circuits S1, S2 approaches the set pressure of the relief valves 35, 36 (i.e., when it becomes equal to or exceeds the predetermined value Pr), merger prohibition control is executed. More specifically, the hydraulic motor 31 for the main hoisting winch 6 is driven only by pressure oil from the hydraulic pump 30, and the hydraulic motor 131 for the auxiliary hoisting winch 7 is driven only by pressure oil from the hydraulic pump 130. This prevents the circuit pressure P from reaching the relief valves 35, 36 and relieving the pressure oil in the circuits, making it less likely that the main hoisting winch 6 and the auxiliary hoisting winch 7 will stop. This allows the bucket 16 to be hoisted stably. Furthermore, according to the first embodiment, the bucket 16 can be hoisted stably.

[0058] Furthermore, once the merger prohibition control is initiated, the control continues until the operation levers 25, 26 are not operated (until step S43 returns No), so the hoisting operation of the bucket 16 can be performed stably.

[0059] Furthermore, in this embodiment, this merger prohibition control (special control) is performed only when the winches 6, 7 are operating in a hoisting motion. Therefore, there is no influence from surge pressure that occurs when the winches 6, 7 are lowered. There is also no influence from other controls during hoisting. In addition, it is possible to reduce the influence when other operations, such as raising and lowering the boom 5, are performed in combination.

[0060] (Second embodiment) Next, a crane according to a second embodiment of the present invention will be described. The crane according to the second embodiment is characterized in that the processing of the merge prohibition control is partially different from that of the first embodiment. Therefore, the following will describe the features of the second embodiment, and will omit a description of the same configuration as the first embodiment.

[0061] Fig. 6 is a flowchart showing the processing procedure of merge prohibition control according to the second embodiment. As shown in Fig. 6, in the second embodiment, a process (step S42-1) for controlling the motor displacement of the hydraulic motors 31, 131 to the small displacement side is added between steps S42 and S43.

[0062] In step S42-1, the controller 60 controls the motor displacement control devices 40, 140 to change the motor displacement of the hydraulic motors 31, 131 to a smaller displacement than before the start of the merger prevention control. That is, the controller 60 controls the hydraulic motors 31, 131 to rotate at a higher speed than before the start of the merger prevention control, thereby increasing the output of the hydraulic motors 31, 131. Explaining this in detail using FIG. 3, the controller 60 controls the opening of the solenoid proportional valve 46 to adjust the force acting on the displacement control spool 44, thereby controlling the motor displacement of the hydraulic motor 31 so that the piston 41 moves in the direction b. The controller 60 also controls the motor displacement of the hydraulic motor 131 to a smaller displacement by the motor displacement control device 140.

[0063] As described above, according to the second embodiment, it is possible to achieve the same operational effects as the first embodiment and to stably hoist up the bucket 16. Moreover, since the hoisting speed of the hydraulic motors 31, 131 can be made faster than in the first embodiment during merger prohibition control, there is also the advantage that the efficiency of excavation work by the crane 1 is improved compared to the first embodiment.

[0064] (Reference to other embodiments) The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the appended claims.

[0065] Furthermore, the operation levers for each winch, such as operation levers 25, 26, may be located not in the cab 9 of the crane 1 but, for example, in a remote control room that is remote from the crane 1. Furthermore, instead of the operation levers 25, 26, a device such as an operation dial may be used, or the hoisting / lowering speed of the winches 6, 7, etc. may be input from an operation unit such as a touch panel or a mobile terminal, and the controller 60 may output a current command value corresponding to the input value (speed value) to the solenoid directional control valves 55, 56. In other words, as a means for specifying the rotation speed of the winches 6, 7, etc., in addition to a means in which the operator gives an instruction using the amount of operation of the operation levers 25, 26, any means may be used, such as an instruction using an operation dial or an instruction by directly inputting a speed value.

[0066] Furthermore, while a crawler crane has been given as an example of a crane, the present invention is not limited to this and can be applied to any type of cranes, including other mobile cranes such as wheel cranes, truck cranes, rough terrain cranes, and all-terrain cranes, as well as foundation machines such as tower cranes, overhead cranes, jib cranes, retractable cranes, stacker cranes, gantry cranes, unloaders, and earth drills. Furthermore, while a grab bucket 16 as shown in Figure 1 has been given as an example of an attachment, the present invention can be applied to any type of attachment that operates with multiple winches, and can also be applied to, for example, clamshells, hammer grabs, and diaphragm wall equipment. [Explanation of symbols]

[0067] 1 crane 2. Running body 3 Swivel device 4 Rotating body 5. Boom 6 Main winch (No. 1 winch) 7 Auxiliary winch (second winch) 8. Hoisting winch 9 Cab 10,11 Sheaves 12 Main winding rope 13 Auxiliary rope 14 Pendant Rope 15. Descending rope 16 Bucket (attachment) 17,18 Sheaves 25,26 Control lever 30 Hydraulic pump (first hydraulic pump) 31 Hydraulic motor (first hydraulic motor) 32 Directional control valve 32a,23b Pressure receiving part 33 Counterbalance valve 34 Tank 35,36 Relief valve 37,38 Main pipeline 40 Motor capacity control device 41 Piston 41a,41b Oil room 42 Load pressure control spool 42a Spring 43 Piston 43a,43b Oil room 44 Tilt control spool 44a Spring 45 piston 45a Oil room 46 Solenoid proportional valve 47 Pilot Pump 50 apertures 51 Pipeline 55,56 Solenoid controlled directional control valve 60 Controller 65,66 Pressure detector 130 Hydraulic pump (second hydraulic pump) 131 Hydraulic motor (second hydraulic motor) 140 Motor capacity control device E1~E5 Electrical wiring L1, L2 center pipe 231 Hydraulic motor (for elevation) 331 Hydraulic motor (for travel) 431 Hydraulic motor (for travel)

Claims

1. a first winch; and a first hydraulic motor that drives the first winch; a second winch; and a second hydraulic motor that drives the second winch and is disposed upstream or downstream of the first hydraulic motor in the flow of pressure oil; a first hydraulic pump that supplies pressure oil to the first hydraulic motor and the second hydraulic motor; a second hydraulic pump that supplies pressure oil to the first hydraulic motor and the second hydraulic motor; an attachment operated by the first winch and the second winch, When the first winch and the second winch are performing a hoisting operation, a crane configured to perform special control to stop the supply of pressurized oil to the second hydraulic motor by the first hydraulic pump and the supply of pressurized oil to the first hydraulic motor by the second hydraulic pump when at least one of the pressure between the first hydraulic motor and the first hydraulic pump and the pressure between the second hydraulic motor and the second hydraulic pump is equal to or higher than a predetermined value.

2. The crane of claim 1, The crane according to claim 1, wherein the predetermined value is less than a set pressure of a relief valve provided on the discharge side of the first hydraulic pump or the discharge side of the second hydraulic pump.

3. The crane according to claim 1 or 2, the first hydraulic motor and the second hydraulic motor are both variable displacement motors, When the special control is started, the output of at least one of the first hydraulic motor and the second hydraulic motor is increased compared to before the special control was started.

4. The crane according to any one of claims 1 to 3, When the special control is executed, the special control is maintained until the first winch and the second winch are not operated.

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