crane

Abstract

To provide a crane capable of obtaining stable swivel characteristics.SOLUTION: A crane includes an engine (10), a main pump (11) driven by the engine, a turning hydraulic motor (20) driven by hydraulic oil discharged from the main pump, a direction control valve (15) actuated by operation of an operation device (35) to control the flow direction of the hydraulic oil supplied from the main pump to the turning hydraulic motor, and a flow control valve (17) to adjust the flow rate of the hydraulic oil supplied from the main pump to the direction control valve such that the longitudinal differential pressure of the direction control valve approaches a preset target value. In this crane, the target value is changed in accordance with the operation amount of the operation device regardless of the engine speed.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] There is known a technique for arbitrarily changing the swing characteristics of a crane. For example, Patent Document 1 describes that "the crane is provided with a hydraulic pump, a swing hydraulic motor driven by pressure oil from the hydraulic pump, an operating member for inputting a swing command, a directional control valve for controlling the flow of pressure oil from the hydraulic pump to the swing hydraulic motor according to the amount of operation of the operating member, and a change means for arbitrarily changing at least one of the starting characteristics and the stopping characteristics. Then, by switching the bleed-off control valve by a control signal from the controller to the electromagnetic proportional valve, the amount of pressure oil supplied to the swing hydraulic motor based on the starting characteristics during the starting operation is controlled, and the amount of pressure oil supplied to the swing hydraulic motor based on the stopping operation during the stopping operation is controlled" (see abstract). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-143635 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the amount of pressurized oil supplied to the rotation hydraulic motor is controlled by switching the bleed-off control valve, so there is a possibility that the rotation characteristics of the crane will become unstable if the discharge flow rate of the hydraulic pump changes.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a crane that can obtain stable turning characteristics. [Means for solving the problem]

[0006] In order to achieve the above object, a representative embodiment of the present invention provides a main pump that is driven by an input of a predetermined rotation speed, a swing hydraulic motor that is driven by pressure oil discharged from the main pump, a directional control valve that is operated by the operation of an operating device and controls the flow direction of pressure oil supplied from the main pump to the swing hydraulic motor, and a directional control valve that controls a flow direction of pressure oil supplied from the main pump to the swing hydraulic motor so that a differential pressure before and after the directional control valve approaches a preset target value. The directional control valve Flow rate of pressure oil supplied to of A crane equipped with a flow control valve for adjusting the flow rate of the the flow rate control valve is provided in an oil passage that branches off from an oil passage connecting the main pump and the directional control valve and is connected to a suction side of the main pump, and is capable of returning pressure oil discharged from the main pump to the suction side of the main pump, The target value is changed in accordance with the amount of operation of the operating device, regardless of the number of rotations of the input.

[0007] According to the present invention, stable turning characteristics can be obtained. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of a crane according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram of a hydraulic circuit that drives a rotation hydraulic motor. [Diagram 3] FIG. 4 is a diagram showing the relationship between the operation amount of a swing operation lever and the set differential pressure of a flow rate control valve. [Figure 4] FIG. 2 is a diagram showing a screen of a display panel. [Diagram 5] FIG. 4 is a diagram showing the relationship between the operation amount of a swing operation lever and the set differential pressure of a flow rate control valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a side view of a crane according to an embodiment of the present invention. The crane according to this embodiment has a running body 101, a rotating body 103 rotatably mounted on the running body 101 via a rotating device 102, a boom 104 attached to the tip of the rotating body 103 so as to be able to rise and fall, and a cab 108. The rotating body 103 rotates in the left-right direction at a desired speed by the rotating device 102. This rotating device 102 includes a hydraulic motor 20 for rotation (see Fig. 2).

[0010] A hoist drum 105 is mounted on the rotating body 103, and a hoist rope 106 is wound or unwound by driving the hoist drum 105, and a load is raised or lowered via a hook 107 suspended from the tip of a boom 104. A driver's cab 108 is provided with a swing operation lever (operating device) 35 that allows an operator to operate the swing body 103 to swing, a controller 30 that controls the crane, a display panel 31, etc. (see FIG. 2). This swing operation lever 35 is, for example, an electric lever. Of course, the swing operation lever 35 may be a hydraulic lever.

[0011] Fig. 2 is a configuration diagram of a hydraulic circuit that drives a swing hydraulic motor 20. The hydraulic circuit shown in Fig. 2 includes a main pump 11, a pilot pump 12, a swing hydraulic motor 20, a directional control valve 15, a flow rate control valve 17, a pressure control valve 18, and a relief valve 16. In Fig. 2, L1 to L8 indicate oil passages, and E1 to E5 indicate electrical wiring. Reference numeral 25 indicates a tank that stores hydraulic oil.

[0012] The main pump 11 is driven by the engine 10 and supplies pressure oil to the directional control valve 15. The discharge flow rate of the main pump 11 is adjusted by a regulator (not shown). The main pump 11 is a variable displacement hydraulic pump. The pilot pump 12 is driven by the engine 10 and supplies pressure oil to the pressure control valve 18. The pilot pump 12 is a fixed displacement hydraulic pump. The rotation speed of the engine 10 is controlled based on the amount of operation of an accelerator grip (not shown) operated by an operator.

[0013] The swing hydraulic motor 20 is driven by pressure oil discharged from the main pump 11. The directional control valve 15 controls the flow direction and flow rate of the pressure oil supplied to the swing hydraulic motor 20. By switching the position (spool position) of the directional control valve 15, the swing hydraulic motor 20 rotates forward or reverse.

[0014] The directional control valve 15 has input units 15a and 15b on the left and right sides for inputting pilot signals (electrical signals). When the swing operation lever 35 is operated, pilot signals Pl and Pr corresponding to the amount of operation are generated by the controller 30. The pilot signals Pl and Pr are input to the input units 15a and 15b via electrical wiring E1 and E2, respectively, and the position of the directional control valve 15 is switched.

[0015] Specifically, the directional control valve 15 is normally in a neutral position O, and when a pilot signal Pl is input to the input port 15a, it switches to the left position A, and when a pilot signal Pr is input to the input port 15b, it switches to the right position B.

[0016] When the directional control valve 15 is in the neutral position O, the pressure oil discharged from the main pump 11 flows from the oil passage L1 to the oil passage L5 and returns to the tank 25. When the directional control valve 15 is switched to the left position A, the pressure oil discharged from the main pump 11 flows from the oil passage L1 to the oil passage L2 and forwardly rotates the swing hydraulic motor 20. The pressure oil discharged from the swing hydraulic motor 20 flows in this order through the oil passage L3 and the oil passage L5 and returns to the tank 25.

[0017] On the other hand, when the directional control valve 15 is switched to the right position B, the pressure oil discharged from the main pump 11 flows from the oil passage L1 to the oil passage L3 to reverse the rotation hydraulic motor 20. The pressure oil discharged from the rotation hydraulic motor 20 flows in this order through the oil passage L2 and the oil passage L5, and returns to the tank 25.

[0018] The flow rate control valve 17 is provided on an oil passage L4 that branches off from an oil passage L1 that connects the main pump 11 and the directional control valve 15 and is connected to the tank 25. The flow rate control valve 17 is normally held in a closing direction by a spring 17a. The flow rate control valve 17 is acted upon by a pressure Ps on the discharge side of the main pump 11, a pressure Pc on the downstream side of the directional control valve 15, and a pressure Pv on the downstream side of the pressure control valve 18. Specifically, the pressure Ps acts in a direction that opens the flow rate control valve 17, and the pressures Pc and Pv act in a direction that closes the flow rate control valve 17.

[0019] Therefore, the flow rate control valve 17 opens and closes depending on the balance between the differential pressure before and after the directional control valve 15 (the difference between pressure Ps and pressure Pc) and the pressure Pv of the pressure oil introduced from the pressure control valve 18. Note that the pressure Pc is affected by the pressure loss of the directional control valve 15, and is therefore lower than the pressure Ps.

[0020] The pressure control valve 18 is provided in the oil passage L6 through which the pressurized oil discharged from the pilot pump 12 flows. In a normal state, the pressure control valve 18 is held at a position where the oil passage L7 and the oil passage L8 communicate with each other, and the pressure Pv is equal to the tank pressure. When a control signal is input from the controller 30 to the pressure control valve 18 via the electric wiring E5, the pressure control valve 18 switches to a position where the oil passage L6 and the oil passage L7 communicate with each other in response to the control signal. As a result, the pressurized oil from the pilot pump 12 is introduced into the flow rate control valve 17.

[0021] The relief valve 16 limits the upper limit of the discharge pressure of the main pump 11 to a set pressure. Therefore, the pressure in the hydraulic circuit shown in FIG.

[0022] Although not shown, the controller 30 is composed of hardware including a CPU that performs various calculations, a storage device such as a ROM or HDD that stores programs for the CPU to execute the calculations, a RAM that serves as a work area when the CPU executes the programs, and a communication interface that is an interface when transmitting and receiving data to and from other devices, and software that is stored in the storage device and executed by the CPU. Each function of the controller 30 is realized by the CPU loading various programs stored in the storage device into the RAM and executing them.

[0023] When an operation command is input from the swing operation lever 35 via the electric wiring E3, the controller 30 generates a control signal according to the operation command and outputs the control signal to the pressure control valve 18. For example, in this embodiment, the controller 30 generates a control signal such that the set pressure of the pressure control valve 18 increases (the value of the pressure Pv acting on the flow rate adjustment valve 17 increases) as the operation amount of the swing operation lever 35 increases. Therefore, when the operation amount of the swing operation lever 35 is small, the setting (target value) of the differential pressure before and after the directional control valve 15 can be reduced, and when the operation amount of the swing operation lever 35 is large, the setting (target value) of the differential pressure before and after the directional control valve 15 can be increased.

[0024] Of course, the controller 30 may generate a control signal that keeps the set pressure of the pressure control valve 18 constant regardless of the amount of operation of the swing operation lever 35.

[0025] A display panel 31 is connected to the controller 30 via electrical wiring E4. The display panel 31 is, for example, a touch-type liquid crystal panel, and an operator can check various settings and conditions of the crane by touching the panel.

[0026] (Operation of hydraulic circuit) Next, the operation of the hydraulic circuit according to this embodiment will be described, taking as an example a case where the operator operates the swing operation lever 35 in the left swing direction in order to swing the swing body 103 left.

[0027] When the operator operates the swing operation lever 35, an operation command from the swing operation lever 35 is input to the controller 30. The controller 30 outputs a pilot signal Pl to the input unit 15a based on the operation command. Then, the directional control valve 15 switches to the left position A, pressure oil from the main pump 11 is supplied to the swing hydraulic motor 20, the swing hydraulic motor 20 is rotationally driven, and the swing body 103 starts swinging to the left.

[0028] Furthermore, the controller 30 generates a control signal for operating the pressure control valve 18 in response to the input operation command, and outputs the control signal to the pressure control valve 18 .

[0029] The pressure control valve 18 operates in accordance with the input control signal to communicate the oil passage L6 with the oil passage L7, and the pressure oil discharged from the pilot pump 12 is introduced into the flow rate adjustment valve 17.

[0030] As a result, the flow rate adjustment valve 17 operates in a closing direction due to the action of the pressure Pv on the downstream side of the pressure control valve 18, and the differential pressure before and after the directional control valve 15 is adjusted to a set differential pressure (a predetermined target value) according to the pressure Pv. Since the pressure Pv is determined according to the amount of operation of the swing operation lever 35, the differential pressure before and after the directional control valve 15 becomes a target value according to the amount of operation of the swing operation lever 35.

[0031] More specifically, since the pressure Pv according to the operation amount of the swing operation lever 35 acts on the flow rate control valve 17, if the differential pressure before and after the direction control valve 15 is smaller than the sum of the pressure Pv and the spring 17a, the flow rate control valve 17 does not operate in the opening direction but operates in the closing direction. As a result, the differential pressure before and after the direction control valve 15 remains unchanged. Then, when the differential pressure before and after the direction control valve 15 exceeds the sum of the pressure Pv and the spring 17a, the flow rate control valve 17 operates in the opening direction, so that the differential pressure before and after the direction control valve 15 is controlled to approach a preset target value, that is, the sum of the pressure Pv and the biasing force of the spring 17a. Then, since the set pressure Pv of the pressure control valve 18 changes according to the operation amount of the swing operation lever 35, the differential pressure before and after the direction control valve 15 is also controlled to approach a target value according to the operation amount of the swing operation lever 35.

[0032] In this way, under the pressure difference between the front and rear of the directional control valve 15 controlled to approach a preset target value in response to the operation of the swing operation lever 35, a desired flow rate of pressurized oil is supplied to the swing hydraulic motor 20 regardless of the rotation speed of the engine 10.

[0033] (effect) Thus, according to this embodiment, the differential pressure before and after the directional control valve 15 is controlled to approach a preset target value regardless of changes in the discharge flow rate of the main pump 11 or changes in the rotation speed of the engine 10. As a result, pressure oil at a flow rate according to the differential pressure before and after the directional control valve 15 is stably supplied from the main pump 11 to the swing hydraulic motor 20. Therefore, for example, even if the rotation speed of the engine 10 is increased to drive the hoist drum 105 at high speed, the swing speed of the swing body 103 does not change, and stable swing characteristics of the crane can be obtained. In addition, the combined operability of the crane is improved.

[0034] In addition, the set differential pressure of the flow rate control valve 17 can be adjusted as desired by a control signal from the controller 30 to the pressure control valve 18, making it possible to realize crane operability that suits the operator's preferences.

[0035] In this embodiment, the setting is made so that the greater the operation amount of the swing operation lever 35, the greater the set differential pressure of the flow rate control valve 17. Therefore, when the swing operation lever 35 is operated with the setting (target value) of the differential pressure before and after the directional control valve 15 reduced, the bypass flow rate (flow rate through the flow rate control valve 17) of the flow rate control valve 17 increases, the torque driving the swing hydraulic motor 20 increases more gradually, and gentle acceleration characteristics are obtained.

[0036] On the other hand, when the pressure difference between the front and rear of the directional control valve 15 is set large and the swing operation lever 35 is operated, the bypass flow rate of the flow control valve 17 decreases, the torque driving the swing hydraulic motor 20 increases significantly, and rapid acceleration characteristics are obtained.

[0037] In this way, according to this embodiment, any desired swing characteristic can be stably obtained according to the operator's preference. In addition, there is an advantage that the operability of the crane can be improved with a simple configuration such as providing the pressure control valve 18.

[0038] (Modification) In the above embodiment, a plurality of modes M1 to M3 having different control characteristics (operating characteristics) of the flow rate control valve 17 may be preset in the controller 30, and when the operator selects a preferred mode on the display panel 31, the flow rate control valve 17 may be configured to operate according to the selected mode.

[0039] 3, three modes M1 to M3 are provided in advance in which the set differential pressure of the flow rate control valve 17 differs according to the amount of operation of the swing operation lever 35. Each of the modes M1 to M3 has a control characteristic in which the set differential pressure of the flow rate control valve 17 increases as the amount of operation of the swing operation lever 35 increases, but the set differential pressure of the flow rate control valve 17 relative to the amount of operation of the swing operation lever 35 differs.

[0040] 4, when the operator touches any one of the modes M1 to M3 on the mode setting screen of the display panel 31, the selected mode is output from the display panel 31 to the controller 30. The controller 30 generates a control signal for the pressure control valve 18 in accordance with the selected mode.

[0041] For example, comparing mode M1 and mode M3, the set differential pressure of the flow rate control valve 17 is larger in mode M1 than in mode M3 for the same operation amount of the swing operation lever 35. Therefore, when mode M1 is selected, the differential pressure before and after the directional control valve 15 is larger, so that even with the same operation amount of the swing operation lever 35, the flow rate of the pressure oil supplied to the swing hydraulic motor 20 is larger, and the swing body 103 can be rotated at a higher speed.

[0042] According to this modification, the turning operation can be more easily performed according to the operator's preference.

[0043] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention, and all technical matters included in the technical ideas described in the claims are the subject of the present invention. The above-described embodiment shows a preferred example, 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 attached claims.

[0044] For example, instead of modes M1 to M3 in Fig. 3, modes M4 to M6 in which the set differential pressure of the flow rate control valve 17 changes stepwise relative to the amount of operation of the swing operation lever 35 can be used as shown in Fig. 5. Also, the controller 30 may store data that maps the relationship between the amount of operation of the swing operation lever 35 and the set differential pressure of the flow rate control valve 17, and the controller 30 may control the operation of the pressure control valve 18 based on the data.

[0045] Also, a dedicated switch or dial for selecting a mode may be provided separately instead of touch operation on the display panel 31. These modes may be configured so that the operator can add, change, or delete them as desired.

[0046] Although 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 wheel cranes, truck cranes, rough terrain cranes, all-terrain cranes, as well as tower cranes, overhead cranes, jib cranes, retractable cranes, stacker cranes, gantry cranes, and unloaders. [Explanation of symbols]

[0047] 10 Engine 11 Main pump 12 Pilot pump 15 Directional control valve 17 Flow control valve 18 Pressure Control Valve 20 Swing hydraulic motor 35 Operating lever (operating device) 30 Controller 31 Display Panel

Claims

1. a main pump that is driven by an input of a predetermined rotation speed; a hydraulic motor for rotation driven by pressure oil discharged from the main pump; a directional control valve that is actuated by operation of an operating device to control the flow direction of pressure oil supplied from the main pump to the swing hydraulic motor; a flow rate control valve that adjusts a flow rate of pressure oil supplied from the main pump to the directional control valve so that a differential pressure before and after the directional control valve approaches a preset target value, the flow rate control valve is provided in an oil passage that branches off from an oil passage connecting the main pump and the directional control valve and is connected to a suction side of the main pump, and is capable of returning pressure oil discharged from the main pump to the suction side of the main pump, A crane characterized in that the target value is changed in accordance with the amount of operation of the operating device, regardless of the input rotation speed.

2. 2. The crane of claim 1, A crane characterized in that the target value is changed so as to increase as the amount of operation of the operating device increases.

3. The crane according to claim 1 or 2, A crane characterized in that a plurality of modes having different control characteristics of the flow rate control valve are preset, and the target value is changed in accordance with a selected mode.

4. The crane according to any one of claims 1 to 3, Further comprising a pilot pump that drives the flow rate control valve, The crane according to claim 1, wherein the pressure oil discharged from the pilot pump is introduced into the flow rate control valve at a pressure corresponding to an amount of operation of the operating device, and acts in a direction to close the flow rate control valve.

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