Braking device of winch

Abstract

The present invention provides a winch brake device capable of improving the operability of a free fall operation of a construction machine. The winch brake device (4) of the present invention is used for a construction machine and generates a braking force according to a braking operation, and comprises: a pressing member (4j) for pressing the brake members (4a, 4b) against each other to generate a braking force; a first brake cylinder (31) for applying a first pressing force to the pressing member for pressing the brake members against each other; and a second brake cylinder (32) for applying a second pressing force different from the first pressing force to the pressing member, wherein the first brake cylinder and the second brake cylinder can independently apply the first pressing force or the second pressing force.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2021-003628 filed on January 13, 2021. The entire contents of the Japanese Patent Application are incorporated herein by reference. Technical Field

[0002] The invention relates to a braking device for a winch of a construction machine. Background Art

[0003] As background technology in this technical field, for example, Patent Document 1 describes a technology in which two brake mechanisms (brake cylinders) are arranged in series to change the brake control characteristics of a crane during non-free fall and the brake characteristics during free fall.

[0004] Patent Document 1: Japanese Patent No. 6645937

[0005] However, since free-fall operations are performed in various applications, cranes are required to have braking characteristics corresponding to various operations (various loads during operations). Summary of the invention

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a winch brake device capable of improving the operability of a free-fall operation of a construction machine (crane, etc.).

[0007] In order to achieve the above-mentioned purpose, one embodiment of the present invention provides a brake device of a winch, which is used for construction machinery and generates a braking force according to a braking operation. The brake device of the winch is characterized in that it comprises: a pressing component, which presses the brake components against each other to generate the braking force; a first brake cylinder, which applies a first pressing force to the pressing component for pressing the brake components against each other; and a second brake cylinder, which applies a second pressing force different from the first pressing force to the pressing component, and the first brake cylinder and the second brake cylinder can independently apply the first pressing force or the second pressing force.

[0008] According to the present invention, the operability of free-fall work of a construction machine (crane, etc.) can be improved. In addition, problems, structures and effects other than the above will become clear from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a side view of the external appearance of a crane equipped with the brake device according to the first embodiment.

[0010] Figure 2 This is a hydraulic circuit diagram of the brake device according to the first embodiment.

[0011] Figure 3(a) is a diagram showing the braking force characteristics of the first piston. Figure 3 (b) is a diagram showing the braking force characteristics of the second piston. Figure 3 (c) is a diagram showing the pressure characteristics of the brake control valve. Figure 3 (d) is a diagram showing the braking control characteristics.

[0012] Figure 4 This is a flowchart showing the procedure of the control process of the brake device by the controller.

[0013] Figure 5 This is a hydraulic circuit diagram of the brake device according to Modification 1-1.

[0014] Figure 6 It is a flowchart showing the procedure of the control process of the brake device involved in the modification 1-2.

[0015] Figure 7 It is a flowchart showing the procedure of the control process of the brake device involved in the modification 1-3.

[0016] Figure 8 This is a hydraulic circuit diagram of a brake device according to a second embodiment.

[0017] Fig. 9 (a) is a diagram showing the control characteristics of the electromagnetic proportional valve. Fig. 9 (b) is a diagram showing the braking control characteristics in heavy excavation mode. Fig. 9 (c) is a diagram showing the brake control characteristics in the light excavation mode.

[0018] Fig.10 (a) is a diagram showing the control characteristics of the electromagnetic proportional valve. Fig.10 (b) is a diagram showing the braking control characteristics in heavy excavation mode. Fig.10 (c) is a diagram showing the brake control characteristics in the light excavation mode.

[0019] In the figure: 1-hydraulic motor, 2-planetary reduction mechanism, 2a-sun gear, 2b-planetary gear, 2c-internal gear, 2d-planetary carrier, 3-reel, 4-brake device, 4a-friction plate (brake component), 4b-dock plate (brake component), 4c-first piston, 4d-second piston, 4e-spring (first spring), 4f-first housing, 4g-wheel carrier shaft, 4h-oil seal, 4i-second housing, 4j-pressing component, 4k-spring (second spring), 4m-first pressure chamber, 4n-second pressure chamber, 5-brake mode switching valve, 6-brake control valve, 6a-brake pedal, 7-motor brake switching valve, 8-motor brake cylinder, 9-pilot pump, 10-tank, 11-control valve, 12-main pump, 13-winch operating lever, 15-operating pressure sensor, 16-brake return Road pressure sensor, 17-brake mode switching switch, 18-controller, 19-cooling oil pump, 20-housing internal pressure protection valve, 21-brake mode switching valve, 22-brake control characteristic switching valve, 23-brake control characteristic switching valve, 24-brake control characteristic switching switch, 25-brake control characteristic switching valve, 26-electromagnetic proportional pressure reducing valve (electromagnetic proportional valve), 27-brake control characteristic adjustment dial, 31-1st brake cylinder, 32-2nd brake cylinder, 100-crane, 101-traveling body, 102-slewing device, 103-slewing body, 104-boom, 108-cab, 105-hoisting winch (winch), 106-reversing winch (winch), 105a-hoisting rope, 110-hook, 106a-reversing rope, B1-brake cylinder port, B2-brake cylinder port. DETAILED DESCRIPTION

[0020] Hereinafter, an embodiment in which the brake device according to the present invention is applied to an example of a construction machine (ie, a crane) will be described with reference to the drawings.

[0021] <First embodiment>

[0022] Figure 1 This is a side view of the appearance of a crane equipped with a brake device according to the first embodiment. The crane 100 includes a traveling body 101, a revolving body 103 which is rotatably provided on the traveling body 101 via a revolving device 102, a boom 104 which is rotatably provided on the revolving body 103 in the vertical direction, and a cab 108 for an operator to ride on. A winch for hoisting (i.e., a hoisting winch 105) and a winch for lifting the boom (i.e., a lifting winch 106) are mounted on the revolving body 103.

[0023] A hoisting rope 105a is wound around the hoisting winch 105. The hoisting rope 105a is wound up or released by the rotation of the hoisting winch 105, so that the hook 110 is raised and lowered via a pulley provided at the front end of the boom 104. A hoisting rope 106a is wound around the hoisting winch 106. The hoisting rope 106a is wound up or released by the rotation of the hoisting winch 106, so that the boom 104 is hoisted via a pulley provided at the front end of the boom 104.

[0024] The cab 108 is provided with: a hoisting operating lever 13 for hoisting and unhoisting the hoisting winch 105; various operating levers (not shown) for performing the slewing operation of the slewing body 103 or the reversing operation of the reversing winch 106 of the boom 104; a controller 18 for controlling the crane 100; a brake mode switching switch 17 for switching the operation mode of the brake device 4; a brake control characteristic switching switch 24 for switching the control characteristic of the brake device 4; and a monitor (not shown) as a notification mechanism, etc. (refer to Figure 2 ).

[0025] Figure 2 FIG. 1 is a hydraulic circuit diagram of a brake device according to a first embodiment of the present invention. Figure 2 1 shows a hydraulic circuit for driving the hoisting winch 105, and omits a hydraulic circuit for driving the inverting winch 106.

[0026] The crane 100 includes a controller 18 for controlling the operation of each part of the crane 100, an engine (not shown), a main pump 12 driven by the engine (not shown), a cooling oil pump 19, and a pilot pump 9. The main pump 12, the cooling oil pump 19, and the pilot pump 9 discharge the working oil in the tank 10 as hydraulic oil.

[0027] Although not shown in the figure, the controller 18 is composed of hardware including: a CPU that performs various operations, a storage device such as a ROM or HDD that stores programs for executing operations based on the CPU, a RAM that serves as a work area when the CPU executes the program, and an interface (i.e., a communication interface) when transmitting and receiving data with other devices; and software stored in the storage device and executed by the CPU. The various functions of the controller 18 are realized by causing the CPU to load various programs stored in the storage device into the RAM and execute them.

[0028] The hoisting winch 105 includes a drum 3, a hydraulic motor 1, a main pump 12, a control valve 11, a planetary reduction mechanism 2, and a brake device 4. The main pump 12 supplies hydraulic oil to the hydraulic motor 1 to drive the hydraulic motor 1, thereby driving the drum 3 to hoist and unwind. The control valve 11 controls the flow of hydraulic oil from the main pump 12 to the hydraulic motor 1. The planetary reduction mechanism 2 transmits the driving force of the hydraulic motor 1 to the drum 3. The brake device 4 brakes the wheel frame shaft 4g of the planetary reduction mechanism 2 to prevent the drum 3 from rotating freely.

[0029] The planetary reduction mechanism 2 is constructed to include a sun gear 2a, a planetary gear 2b and an internal gear 2c. The output shaft of the hydraulic motor 1 is connected to the sun gear 2a of the planetary reduction mechanism 2. The sun gear 2a meshes with the planetary gear 2b, and the planetary gear 2b meshes with the internal gear 2c provided on the inner circumference of the drum 3. The planetary gear 2b is supported by the planetary carrier 2d. The carrier shaft 4g to which the planetary carrier 2d is fixed is supported by bearings inside the brake device 4. The outer circumferential surface of the carrier shaft 4g and the through hole through which the carrier shaft 4g is inserted are sealed by an oil seal 4h.

[0030] In the following, for the sake of convenience, the rotation axis direction of the hoisting winch 105 (i.e., the center axis direction of the wheel frame shaft 4g) is referred to as the axial direction. In addition, the side of the two axial ends of the hoisting winch 105 where the output shaft of the hydraulic motor 1 is arranged is referred to as the front side of the hoisting winch 105, and the side opposite thereto in the axial direction is referred to as the rear side of the hoisting winch 105.

[0031] (Structure of brake device)

[0032] The brake device 4 also has the function of a clutch device that transmits or blocks the rotation between the hydraulic motor 1 and the drum 3. That is, the brake device 4 functions as a clutch and a parking brake during power hoisting and stopping, and functions as a service brake during free fall. In addition, in this specification, the braking force required when the brake device 4 is used as a clutch is defined as "necessary clutch force".

[0033] The brake device 4 applicable to this embodiment is a negative control type and is a wet multi-disc brake having a plurality of friction plates 4a. The brake device 4 mainly comprises a plurality of friction plates (brake components) 4a, a plurality of docking plates (brake components) 4b engaged with the plurality of friction plates 4a, a first brake cylinder 31, a second brake cylinder 32, a wheel carrier shaft 4g, an oil seal 4h and a pressing component 4j.

[0034] The plurality of friction plates 4a are mounted on the outer periphery of the wheel carrier shaft 4g by spline connection so as to be movable in the axial direction but limited in the rotational direction. On the other hand, the plurality of docking plates 4b are alternately arranged with the plurality of friction plates 4a in the axial direction, and the plurality of docking plates 4b are mounted on the inner periphery of the housing by spline connection so as to be freely movable in the axial direction but limited in the rotational direction. By applying a pressing force to the docking plates 4b, the friction torque generated between the docking plates 4b and the friction plates 4a is transmitted to the wheel carrier shaft 4g, thereby generating a braking force.

[0035] The butt plates 4b are connected to each other by a spring. Therefore, in the brake release state, the butt plates 4b move in a direction away from each other, thereby forming a gap between the friction plate 4a and the butt plate 4b. By forming a gap between the friction plate 4a and the butt plate 4b, the drag torque (rotational resistance caused by the viscosity of the oil between the friction plate 4a and the butt plate 4b (so-called braking torque)) during free fall is reduced.

[0036] The first brake cylinder 31 includes a first piston 4c, a plurality of springs (first springs) 4e for pressing the first piston 4c, a first housing 4f for accommodating the first piston 4c, and an annular space (ie, a first pressure chamber 4m) formed between the first housing 4f and the first piston 4c.

[0037] The second brake cylinder 32 includes a second piston 4d, a plurality of springs (second springs) 4k for pressing the second piston 4d, a second housing 4i for accommodating the second piston 4d, and an annular space (ie, a second pressure chamber 4n) formed between the second housing 4i and the second piston 4d.

[0038] The first piston 4c is pushed forward in the axial direction by a first pressing force by a plurality of springs 4e. The second piston 4d is arranged inside the first piston 4c and coaxially with the first piston 4c. Similarly to the first piston 4c, the second piston 4d is pushed forward in the axial direction by a second pressing force by a plurality of springs 4k ( Figure 2 Moreover, the first piston 4c and the second piston 4d can press the pressing member 4j independently.

[0039] Here, the spring 4e that pushes the first piston 4c and the spring 4k that pushes the second piston 4d have the same linear characteristics and the same spring performance (spring constant), but the number of springs 4e and 4k is different. That is, in the present embodiment, the spring 4e and the spring 4k have the same spring characteristics (characteristics of deformation when force is applied and restoration when force is removed). Of course, the spring 4e and the spring 4k may also have nonlinear characteristics and may have different spring constants. Furthermore, the number of springs 4e and 4k may also be the same.

[0040] In the present embodiment, the number of springs 4e that push the first piston 4c is greater than the number of springs 4k that push the second piston 4d. More specifically, the ratio of the number of springs 4e to the number of springs 4e is 6:4. Therefore, the pressing force of the first piston 4c pressing the docking plate 4b is 1.5 times greater than that of the second piston 4d. In other words, the first piston 4c can generate a braking force that is 1.5 times greater than that of the second piston 4d. In addition, the total value of the braking force of the two brake cylinders 31 and 32 is set to be equal to the necessary clutch force. Therefore, the necessary clutch force is distributed to the first brake cylinder 31 and the second brake cylinder 32 in a ratio of 6:4. In other words, the total of the forces of the springs 4e and 4k is equal to the pressing force required to generate the necessary clutch force.

[0041] Hydraulic oil is supplied from the brake cylinder port B1 to the first pressure chamber 4m. Hydraulic oil is supplied from the brake cylinder port B2 to the second pressure chamber 4n. If hydraulic oil is supplied to the first pressure chamber 4m, the first piston 4c is pressed toward the rear side in the axial direction. If hydraulic oil is supplied to the second pressure chamber 4n, the second piston 4d is pressed toward the rear side in the axial direction. Therefore, in a state where the first piston 4c and the second piston 4d are pressed toward the rear side in the axial direction, the braking force of the brake device 4 is minimum, and if the first piston 4c or the second piston 4d is pressed toward the front side in the axial direction, the braking force based on the brake device 4 becomes maximum.

[0042] In addition, the ratio (A1 / A2) of the pressure area A1 of the hydraulic oil acting on the first pressure chamber 4m and the pressure area A2 of the hydraulic oil acting on the second pressure chamber 4n is equal to the ratio of the pressing force of the first piston 4c to the pressing force of the second piston 4d. As described above, in the present embodiment, since the ratio of the number of springs 4e pushing the first piston 4c to the number of springs 4k pushing the second piston 4d is 6:4, the ratio of the pressure area A1 to the pressure area A2 is also 6:4. Thus, a braking force proportional to the amount of depression of the brake pedal 6a can be generated. In other words, the ratio of the braking force proportional to the amount of depression of the brake pedal 6a is also 6:4.

[0043] In addition, the ratio of the pressing force of the first piston 4c to the pressing force of the second piston 4d and the ratio of the pressure-bearing area A1 of the first pressure chamber 4m to the pressure-bearing area A2 of the second pressure chamber 4n do not necessarily have to be consistent. For example, the ratio of the pressing force and the ratio of the pressure-bearing area may differ within a range of ±10% (preferably a range of ±5%). This includes the case where the pressure loss caused by the piston seals installed in the brake cylinders 31 and 32 in the two pressure chambers 4m and 4n is taken into consideration, so that the effective pressure-bearing area is actively adjusted to the required ratio.

[0044] The pressing member 4j is arranged to be able to abut against the first piston 4c and the second piston 4d, and the abutting plate 4b is always pressed by the force of the spring 4e acting on the first piston 4c and the force of the spring 4k acting on the second piston 4d. That is, the brake device 4 always generates a braking force (negative brake) by the pressing force acting on the pressing member 4j toward the axial front side. In addition, as long as the pressing member 4j can abut against the first piston 4c and the second piston 4d at the same time, its shape is not limited.

[0045] The brake cylinder port B1 is connected to the pilot pump 9 via the brake control valve 6, the brake mode switching valve 5 and the brake control characteristic switching valve 22, and is connected to the pilot pump 9 via the brake mode switching valve 21 and the brake control characteristic switching valve 23. Thus, the brake cylinder port B1 can selectively supply the hydraulic oil whose pressure is adjusted by the brake control valve 6 and the hydraulic oil discharged from the pilot pump 9.

[0046] Furthermore, the brake cylinder port B2 is also connected to the pilot pump 9 via the brake control valve 6, the brake mode switching valve 5 and the brake control characteristic switching valve 22, and is also connected to the pilot pump 9 via the brake mode switching valve 21 and the brake control characteristic switching valve 23. Thus, the brake cylinder port B2 can also selectively supply the hydraulic oil whose pressure is adjusted by the brake control valve 6 and the hydraulic oil discharged from the pilot pump 9.

[0047] Here, in order to cool the brake device 4, the cooling oil (hydraulic oil) is forced to circulate by the cooling oil pump 19. Specifically, the cooling oil discharged from the cooling oil pump 19 is supplied to the inside of the brake device 4 from the IN port, absorbs the heat of the brake disc (friction plate 4a and docking plate 4b), and is discharged from the OUT port and returned to the tank 10. The upper limit of the discharge pressure of the cooling oil pump 19 is limited by the safety valve (i.e., the housing internal pressure protection valve 20). Therefore, the internal pressure of the brake device 4 is also maintained below the upper limit of the housing internal pressure protection valve 20. In addition, the positional relationship between the IN port and the OUT port can also be configured to be opposite to that of the present embodiment.

[0048] (Hydraulic circuit structure)

[0049] The hydraulic circuit driving the hoisting winch 105 is provided with a motor brake switching valve 7 switched and controlled by the operation of the hoisting operating lever 13, a motor brake cylinder 8, a brake control valve 6 operated by the brake pedal 6a, brake mode switching valves 5, 21 and brake control characteristic switching valves 22, 23 switched and controlled by the controller 18, and a housing internal pressure protection valve 20. In addition, the brake control valve 6 can be a structure that works according to the brake operation, and can be a structure that works according to the pedaling amount of the brake pedal 6a, a structure that works according to the pedaling force of the brake pedal 6a, or a structure that replaces the operation with a manual operation, or a structure that works according to the rotation speed of the hoisting winch 105.

[0050] Furthermore, in the hydraulic circuit, a plurality of operating pressure sensors 15 and a brake circuit pressure sensor 16 are provided in order to switch the brake mode switching valves 5 and 21 and thus switch the operation mode (neutral brake mode / neutral free mode) of the brake device 4, and these sensors are respectively connected to the controller 18. In addition, the controller 18 is connected to a brake mode switching switch 17 and a brake control characteristic switching switch 24.

[0051] The brake mode switching switch 17 is a switch for selecting the operation mode to be set to either the neutral brake mode or the neutral free mode described below, and the brake control characteristic switching switch 24 is a switch for selecting the operation mode to be set to either the heavy excavation mode or the light excavation mode described below.

[0052] (Operation of the hydraulic circuit)

[0053] Next, the operation of the hydraulic circuit in the operation mode for performing power hoisting and unwinding (ie, neutral brake mode) and the operation of the hydraulic circuit in the operation mode for performing free fall (ie, neutral free mode) will be described. Figure 2 The state of the neutral braking mode is shown in FIG. If the braking mode switching switch 17 is switched to the operating position of the neutral braking mode, Figure 2 As shown, the brake mode switching valves 5, 21 and the brake control characteristic switching valves 22, 23 are in a non-excited state. In this state, if the brake mode switching switch 17 is switched to the operation position of the neutral free mode and other conditions are met, the brake mode switching valves 5, 21 are excited and the operation mode is switched to the neutral free mode.

[0054] -Power winch and unwinding action (neutral braking mode)-

[0055] like Figure 2When the hoisting operating lever 13 shown is operated to the hoisting position or the unwinding position, the pilot pressure from the pilot pump 9 acts on the control valve 11 to drive the valve column of the control valve 11, and the hydraulic oil discharged from the main pump 12 through the control valve 11 is supplied to the hydraulic motor 1. At the same time, the pilot pressure from the pilot pump 9 also acts on the motor brake switching valve 7 via the high-pressure selection valve 14. As a result, the motor brake switching valve 7 is switched to position (A), and the pilot pressure from the pilot pump 9 drives the motor brake cylinder 8 to the brake release side, so that the hydraulic motor 1 is driven to rotate. In addition, the motor brake switching valve 7 can also be an electromagnetic switching valve that is electrically switched according to the detection signal of the operating pressure sensor 15.

[0056] In the neutral braking mode, the braking mode switching valves 5 and 21 and the braking control characteristic switching valves 22 and 23 are in a non-excitation state. Therefore, the braking mode switching valves 5 and 21 are switched to positions (D1) and (D2), respectively, and the braking control characteristic switching valves 22 and 23 are switched to positions (E1) and (E2), respectively. In addition, the braking control characteristic switching valves 22 and 23 do not necessarily have to be switched to positions (E1) and (E2). That is, the neutral braking mode can also be started when the braking control characteristic switching valves 22 and 23 are in positions (F1) and (F2), respectively.

[0057] The brake release pressure (i.e., the pilot pressure from the pilot pump 9) is cut off by the brake mode switching valves 5 and 21, and the first pressure chamber 4m and the second pressure chamber 4n are connected to the tank 10. The first pressure chamber 4m and the second pressure chamber 4n become tank pressure, and the spring 4e pushes the first piston 4c, and the spring 4k pushes the second piston 4d. The force of the springs 4e and 4k acting on the first piston 4c and the second piston 4d is transmitted to the pressing member 4j, and the pressing member 4j presses the docking plate 4b. As a result, the friction plate 4a and the docking plate 4b are pressed against each other, thereby applying a braking force to the planetary carrier 2d, and the planetary carrier 2d is fixed.

[0058] In the neutral brake mode, when the sun gear 2a of the planetary reduction mechanism 2 is rotated by the rotational driving force of the hydraulic motor 1, the planetary gear 2b rotates to rotate the internal gear 2c and the drum 3 connected to the internal gear 2c, thereby performing power-based hoisting or unwinding.

[0059] -Freefall Actions (Neutral Free Mode)-

[0060] If the hoisting operating lever 13 is operated to the neutral position, the hydraulic oil flowing from the main pump 12 to the hydraulic motor 1 is blocked by the control valve 11. Since the pilot hydraulic oil is no longer supplied to the motor brake switching valve 7 via the high-pressure selection valve 14, the motor brake switching valve 7 is switched to position (B). Since the motor brake switching valve 7 blocks the pilot pressure flowing to the motor brake cylinder 8, the motor brake works by the force of the spring. In this state, if the brake mode switching valves 5 and 21 are energized and the braking force of the brake device 4 is released, the drum 3 rotates freely based on the deadweight of the hanging object suspended on the hook 110.

[0061] The switching to the neutral free mode is performed as follows: the controller 18 issues a command to operate the brake mode switching valves 5 and 21 based on the respective judgment values ​​of the operating pressure sensor 15, the brake circuit pressure sensor 16, and the brake mode switching switch 17, thereby switching to the neutral free mode. For example, in a state where the operating pressure detected by the operating pressure sensor 15 is less than a preset threshold value (i.e., the hoisting operating lever 13 is neutral) and the circuit pressure detected by the brake circuit pressure sensor 16 is less than a preset threshold value (i.e., the brake pedal 6a is stepped on), if it is detected that the brake mode switching switch 17 is switched to the operating position of the neutral free mode, the controller 18 switches the operation mode from the neutral brake mode to the neutral free mode.

[0062] Here, in the present embodiment, as the working modes in the neutral free mode, a heavy excavation mode (first working mode) and a light excavation mode (second working mode) are prepared in advance. The heavy excavation mode is a mode suitable for making a heavy object fall by its own weight (heavy load operation), and the light excavation mode is a mode suitable for making a light object fall by its own weight (light load operation). Specifically, the braking control characteristics are different in the heavy excavation mode and the light excavation mode, and the braking force in the heavy excavation mode is set to be greater than the braking force in the light excavation mode. The operation of the hydraulic circuit in each excavation mode is described below.

[0063] -Heavy Digging Mode-

[0064] If the brake control characteristic switching switch 24 is switched to the heavy excavation mode position, the operation mode is switched to the heavy excavation mode. In the heavy excavation mode, the brake mode switching valves 5 and 21 are in the energized state, and the brake control characteristic switching valves 22 and 23 are in the non-energized state. That is, in the heavy excavation mode, the brake mode switching valves 5 and 21 are switched to the positions (C1) and (C2), respectively, and the brake control characteristic switching valves 22 and 23 are switched to the positions (E1) and (E2), respectively.

[0065] In this way, the pilot pressure (pilot pressure corresponding to the amount of depression of the brake pedal 6a) adjusted by the brake control valve 6 is applied to the brake mode switching valve 5, and the brake release pressure (maximum pressure), that is, the pilot pressure from the pilot pump 9, is directly applied to the brake mode switching valve 21. The pilot pressure adjusted by the brake control valve 6 acts on the first pressure chamber 4m via the brake cylinder port B1. Therefore, the first piston 4c presses the pressing member 4j with a pressing force corresponding to the difference between the force of the spring 4e and the pilot pressure acting on the first pressure chamber 4m.

[0066] On the other hand, the pilot pressure (brake release pressure) from the pilot pump 9 directly acts on the second pressure chamber 4n via the brake cylinder port B2. More specifically, the maximum discharge pressure of the pilot pump 9 acts on the second pressure chamber 4n. Therefore, the second piston 4d is held at the rear side in the axial direction ( Figure 2 ), so the braking based on the second piston 4d is released.

[0067] Thus, in the heavy excavation mode, the first brake cylinder 31 and the second brake cylinder 32 operate independently, and only the braking force is generated by the first brake cylinder 31. The braking force in the heavy excavation mode follows the spring characteristics of the spring 4e pressing the first piston 4c.

[0068] -Light mining mode-

[0069] If the brake control characteristic switching switch 24 is switched to the light excavation mode position, the operation mode is switched to the light excavation mode. In the light excavation mode, the brake mode switching valves 5 and 21 are in the energized state, and the brake control characteristic switching valves 22 and 23 are in the energized state. That is, in the light excavation mode, the brake mode switching valves 5 and 21 are switched to the positions (C1) and (C2), respectively, and the brake control characteristic switching valves 22 and 23 are switched to the positions (F1) and (F2), respectively.

[0070] Thus, the pilot pressure (pilot pressure corresponding to the amount of depression of the brake pedal 6a) adjusted by the brake control valve 6 is applied to the brake mode switching valve 5, and the brake release pressure, that is, the pilot pressure from the pilot pump 9, is directly applied to the brake mode switching valve 21. In the light excavation mode, the positions of the brake control characteristic switching valves 22 and 23 are switched to positions (F1) and (F2), respectively, so that the pilot pressure adjusted by the brake control valve 6 acts on the second pressure chamber 4n through the brake cylinder port B2. Therefore, the second piston 4d presses the pressing member 4j with a pressing force corresponding to the difference between the acting force of the spring 4k and the pilot pressure acting on the second pressure chamber 4n.

[0071] On the other hand, the pilot pressure (brake release pressure) from the pilot pump 9 directly acts on the first pressure chamber 4m via the brake cylinder port B1. More specifically, the maximum discharge pressure of the pilot pump 9 acts on the first pressure chamber 4m. Therefore, the first piston 4c is held at the rear side in the axial direction ( Figure 2 ), so the braking based on the first piston 4c is released.

[0072] Thus, in the light excavation mode, the second brake cylinder 32 and the first brake cylinder 31 operate independently, and only the braking force is generated by the second brake cylinder 32. Moreover, the braking force in the light excavation mode follows the spring characteristics of the spring 4k that pushes the second piston 4d. In this way, by exciting the brake control characteristic switching valve 22 and the brake control characteristic switching valve 23, the brake cylinders 31 and 32 that generate the braking force are selectively switched.

[0073] Next, refer to Figure 3 Various characteristics of the brake device 4 according to the present embodiment will be described. Figure 3 (a) is a diagram showing the braking force characteristics of the first piston 4c, wherein the horizontal axis represents the pressure acting on the first pressure chamber 4m, and the vertical axis represents the braking force by the first piston 4c. Figure 3 (b) is a graph showing the braking force characteristics of the second piston 4d, wherein the horizontal axis represents the pressure acting on the second pressure chamber 4n, and the vertical axis represents the braking force by the second piston 4d.

[0074] As described above, in this embodiment, the ratio of the number of springs 4e pressing the first piston 4c to the number of springs 4k pressing the second piston 4d is 6:4. Therefore, if the necessary clutch force is set to 100% (the maximum value of the braking force), the braking force of the first piston 4c is proportionally distributed to a maximum of 60% of the necessary clutch force (reference Figure 3 In (a), the braking force of the second piston 4d is 40% of the necessary clutch force at most (reference Figure 3 (b)). Moreover, the spring 4e has a linear characteristic, so as the pressure acting on the first pressure chamber 4m increases, the braking force of the first piston 4c decreases linearly. Similarly, as the pressure acting on the second pressure chamber 4n increases, the braking force of the second piston 4d also decreases linearly.

[0075] The braking force characteristics of the first piston 4c and the braking force characteristics of the second piston 4d can be adjusted by changing the spring characteristics of the spring 4e and the spring 4k and the pressure receiving area of ​​the first piston 4c or the second piston 4d.

[0076] Figure 3(c) is a diagram showing the pressure characteristics of the brake control valve 6. The horizontal axis represents the pedal stroke. The pedal stroke represents the ratio of the pedal stroke (depression amount) when the brake pedal 6a is fully depressed as 100% and the non-operation state of the brake pedal 6a is not depressed as 0%.

[0077] like Figure 3 As shown in (c), the pressure characteristic of the brake control valve 6 is as follows: within the range of 0% to 100% of the pedal stroke, the pressure decreases linearly as the pedal stroke increases. In addition, the pressure characteristic of the brake control valve 6 does not necessarily need to be a characteristic in which the pressure decreases linearly as the pedal stroke increases.

[0078] Figure 3 (d) is a diagram showing the braking control characteristics, where the horizontal axis represents the pedal stroke and the vertical axis represents the braking force. Figure 3 In (d), the ratio of the braking force when the necessary clutch force is set to 100% is shown. Figure 3 As shown in (d), in the heavy excavation mode, the braking force increases linearly in the range of 0% to 60% as the pedal stroke increases. On the other hand, in the light excavation mode, the braking force increases linearly in the range of 0% to 40% as the pedal stroke increases. Moreover, if the pedal stroke is detected to be 100%, the brake mode switching valves 5 and 21 immediately become non-excitation states and are temporarily switched to the neutral brake mode. Therefore, the first brake cylinder 31 and the second brake cylinder 32 cooperate to generate the braking force, and the braking force becomes the necessary clutch force (100%).

[0079] As described above, in the present embodiment, within the range of the pedal stroke from 0% to 100%, the braking force can be generated with different brake control characteristics in the heavy excavation mode and the light excavation mode.

[0080] Next, control of the brake device 4 by the controller 18 will be described. Figure 4 4 is a flowchart showing the control process of the brake device 4 by the controller 18. Figure 4 As shown, first, the controller 18 reads the current setting value of the brake control characteristic stored in the RAM (S101). That is, the controller 18 determines whether the current operation mode is the heavy excavation mode or the light excavation mode.

[0081] Next, the controller 18 performs a braking mode determination to determine whether the current operation mode is the neutral free mode or the neutral braking mode (S102). When the braking mode determination result is the neutral braking mode, the controller 18 performs an operation determination to determine whether the braking control characteristic switching switch 24 is operated (S103). If the controller 18 determines that the operation of switching to the light excavation mode is performed based on the input signal from the braking control characteristic switching switch 24, the controller 18 outputs a command to energize the braking control characteristic switching valves 22 and 23 (S104).

[0082] Here, the present embodiment is configured such that, even if it is determined in S102 that the mode is temporarily switched to the neutral braking mode during the hoisting operation, the mode is switched to the light excavation mode or the heavy excavation mode by operating the brake control characteristic switching switch 24. However, the switching of the working mode may be prohibited or invalidated when the mode is temporarily switched to the neutral braking mode. In other words, the brake control characteristic switching switch 24 may be enabled only in the permanent neutral braking mode.

[0083] Next, the controller 18 writes the setting value of the brake control characteristic (light excavation mode at this time) into the RAM, thereby updating the setting value (S105). Next, the controller 18 displays the setting of the brake control characteristic on the monitor in the cab 108 (S106). That is, the controller 18 displays on the monitor whether it is in the heavy excavation mode or in the light excavation mode.

[0084] On the other hand, if the controller 18 determines in S103 that the operation to switch to the heavy excavation mode has been performed, it outputs a command not to energize the brake control characteristic switching valves 22 and 23 (S107), and then proceeds to S105.

[0085] Furthermore, in S102, if the result of the determination of the braking mode is the neutral free mode, the controller 18 performs an operation determination to determine whether the braking control characteristic switching switch 24 is operated (S108), and if it is determined that the operation is performed ("Yes" in S108), a warning display to the effect that the braking control characteristic cannot be changed (switching between the heavy excavation mode and the light excavation mode) is displayed on the monitor (S109), and the operation of the braking control characteristic switching switch 24 is set to be invalid. That is, the switching between the heavy excavation mode and the light excavation mode is prohibited during the neutral free mode.

[0086] On the other hand, if the controller 18 determines in S108 that the brake control characteristic changeover switch 24 has not been operated (NO in S108), the process ends.

[0087] According to the first embodiment having the above-described structure, the following effects can be obtained.

[0088] The brake device 4 includes a first brake cylinder 31 and a second brake cylinder 32, and the first brake cylinder 31 and the second brake cylinder 32 can independently press the pressing member 4j to generate a braking force. In addition, the braking characteristics based on the first brake cylinder 31 and the braking characteristics based on the second brake cylinder 32 are different (the number of springs 4e and springs 4k is different). Therefore, the operator can operate the crane 100 while generating a braking force based on the braking characteristics of the first brake cylinder 31 according to the work content, and can also operate the crane 100 while generating a braking force based on the braking characteristics of the second brake cylinder 32. Therefore, the operability of the crane 100 during the free fall operation is improved.

[0089] In particular, when the suspended object is heavy, the operator can select the heavy excavation mode to generate a greater braking force than the light excavation mode, so that the brake pedal 6a can be operated in accordance with the operator's feeling. On the contrary, when the suspended object is light, the operator can select the light excavation mode, whereby even if the brake pedal 6a is stepped on by a predetermined amount, only a smaller braking force than the heavy excavation mode is generated, so the operability in the light load operation is also improved. In this way, in the present embodiment, even if there is only one brake device 4, one of the two different braking characteristics can be selected according to the load of the suspended object to perform the free fall operation well.

[0090] In addition, in the first embodiment, since the braking characteristics of the brake device 4 are physically (mechanically) switched by switching between the first brake cylinder 31 and the second brake cylinder 32, the reliability is high. If the pressure of the hydraulic oil acting on the first brake cylinder 31 and the second brake cylinder 32 is controlled by electricity, if the electronic device fails, the braking force may not be ensured, so it is not suitable for use as a brake device requiring high safety. However, if the structure like the first embodiment is adopted, since the braking characteristics are physically (mechanically) switched, there is no need to worry about the above-mentioned problem.

[0091] Furthermore, the selection of the heavy excavation mode and the light excavation mode is controlled to be performed only during the neutral braking mode in the braking mode determination (S102). Therefore, the safety of the operation is improved. Specifically, in the neutral free mode, the suspended object falls due to its own weight. Therefore, if the action mode is switched to the heavy excavation mode or the light excavation mode during this period, the operator needs to adjust the amount of depression of the brake pedal 6a due to the different braking characteristics. Moreover, due to the responsiveness when the action mode is switched, the action of the hydraulic circuit may be temporarily unstable. In this regard, the present embodiment adopts a structure in which the heavy excavation mode and the light excavation mode can only be selected during the neutral braking mode, so it has the advantage of not having to consider the above-mentioned problems and being able to perform operations safely.

[0092] Furthermore, if switching from the heavy excavation mode to the light excavation mode is prohibited and switching from the light excavation mode to the heavy excavation mode is enabled during the neutral free mode, safety can be ensured and operability for the operator can be further improved.

[0093] Furthermore, since the information indicating whether the crane is in the heavy excavation mode or the light excavation mode, various warning information, etc. are displayed on the monitor, the operator can easily recognize the operation mode with the naked eye, and the operability of the crane 100 is further improved. In addition, a warning may be issued by a notification mechanism such as a buzzer or an indicator light instead of the warning display based on the monitor.

[0094] Furthermore, in the first embodiment, when the pedal stroke is detected to be 100%, the brake mode switching valves 5 and 21 are immediately de-energized and temporarily switched to the neutral brake mode, thereby generating a braking force equal to the required clutch force (100%). Therefore, the crane 100 can be safely operated. Of course, a structure may be adopted in which a braking force lower than the required clutch force is generated when the pedal stroke is 100%.

[0095] Here, various modifications can be made to the brake device 4 according to the first embodiment, as specifically described below.

[0096] (Variant 1-1)

[0097] Figure 5 1 is a hydraulic circuit diagram of the brake device 4 according to Modification 1-1. Figure 5 The feature of the modified example 1-1 shown is that, instead of Figure 2 In place of the brake control characteristic switching valves 22 and 23 shown in the figure, a brake control characteristic switching valve 25 is provided which integrates the functions of the brake control characteristic switching valves 22 and 23 .

[0098] Figure 5 The brake control characteristic switching valve 25 shown is in a non-excitation state, and the brake control characteristic switching valve 25 is switched to position (G2). In this state, if the brake mode switching valves 5 and 21 are excited, the pilot pressure adjusted by the brake control valve 6 acts on the first pressure chamber 4m, and the pilot pressure (brake release pressure) discharged from the pilot pump 9 acts on the second pressure chamber 4n. As a result, the braking force based on the first brake cylinder 31 is generated according to the amount of depression of the brake pedal 6a. Therefore, when the brake control characteristic switching valve 25 is in a non-excitation state, it is a heavy excavation mode.

[0099] On the other hand, when the operation mode is switched from the heavy excavation mode to the light excavation mode, the controller 18 outputs a command to energize the brake control characteristic switching valve 25. In this way, the brake control characteristic switching valve 25 is switched from the position (G2) to the position (G1). In this way, the pilot pressure adjusted by the brake control valve 6 acts on the second pressure chamber 4n, and the pilot pressure (brake release pressure) discharged from the pilot pump 9 acts on the first pressure chamber 4m. Thus, the braking force based on the second brake cylinder 32 is generated according to the amount of depression of the brake pedal 6a.

[0100] Thus, the brake device 4 according to the modification 1-1 also exhibits the same effects as those of the first embodiment. In the modification 1-1, the number of brake control characteristic switching valves is small, so there is also an advantage that the hydraulic circuit structure can be simplified.

[0101] (Variation 1-2)

[0102] Figure 6 FIG. 4 is a flowchart showing the control process of the brake device 4 according to the modification 1-2. Figure 6 As shown, first, the controller 18 reads the current setting value of the brake control characteristic (heavy excavation mode or light excavation mode) stored in the RAM (S201). Then, the controller 18 performs a brake mode determination to determine whether the current operation mode is the neutral free mode or the neutral brake mode (S202).

[0103] When the result of the braking mode determination is the neutral free mode, the controller 18 determines whether the setting value of the braking control characteristic read in S201 is the control characteristic determination of the heavy excavation mode and the light excavation mode (S203). If it is determined in S203 that it is the light excavation mode, the controller 18 determines whether the hoisting operation is performed (S204). Specifically, the controller 18 determines whether the hoisting operation based on the hoisting operating lever 13 is performed based on the detection signal input from the operating pressure sensor 15.

[0104] If "yes" in S204, the controller 18 detects the load (load of the hanging object) acting on the hoist rope 105a through a load detector (not shown), and determines whether to allow the free fall of the hanging object based on the detected value (S205). If the detected value of the load detector is less than the threshold value, the controller 18 outputs an instruction to excite the brake control characteristic switching valves 22 and 23 (S206).

[0105] On the other hand, if the detection value of the load detector is above the threshold value, the controller 18 displays a warning on the monitor that the mode needs to be changed to the heavy excavation mode (S207). Then, the controller 18 outputs an instruction to de-energize the brake control characteristic switching valves 22 and 23 (S208), and writes the set value of the brake control characteristic to the RAM (S209). At this time, the heavy excavation mode is written to the RAM. In addition, the controller 18 displays the current brake control characteristic on the monitor (S210). Specifically, the controller 18 displays on the monitor that the current operation mode is the heavy excavation mode or the light excavation mode.

[0106] If it is determined in S202 that the mode is in the neutral braking mode, if it is determined in S203 that the mode is in the heavy excavation mode, or if it is determined in S204 that the hoisting operation is not being performed (No in S204 ), the controller 18 ends the processing.

[0107] In this variation 1-2, when the current action mode is the neutral free mode and the light excavation mode, the operation of the hoisting operating lever 13 and the load of the suspended object acting on the hoisting rope 105a are detected (S204, S205), and when the load of the suspended object is less than the threshold value, the light excavation mode is maintained and the brake control characteristic switching valves 22 and 23 are energized (S206), and when the load of the suspended object is above the threshold value, the brake control characteristic switching valves 22 and 23 are automatically de-energized, thereby transferring to the heavy excavation mode (S208). Therefore, it is easy to use for the operator and has excellent safety.

[0108] In addition, in modification 1-2, the controller 18 can not only store the state of automatically switching to the heavy excavation mode in S208 in the RAM and reflect it in the next hoisting operation, but also set it to be limited to the processing in the current hoisting operation. In addition, the load of the hanging object can also be detected by a detector other than the load detector.

[0109] (Variation 1-3)

[0110] Figure 7 FIG. 4 is a flowchart showing the control process of the brake device 4 according to the modification 1-3. Figure 7As shown, first, the controller 18 reads the current setting value of the brake control characteristics (heavy excavation mode or light excavation mode) stored in the RAM (S301), and then determines whether the setting value of the brake control characteristics read is the control characteristics of the heavy excavation mode or the light excavation mode (S302). If it is determined in S302 that it is the light excavation mode, the controller 18 outputs an instruction to energize the brake control characteristics switching valves 22 and 23 (S303). On the other hand, if it is determined in S302 that it is the heavy excavation mode, the controller 18 outputs an instruction to de-energize the brake control characteristics switching valves 22 and 23 (S304). In addition, the controller 18 displays the current brake control characteristics on the monitor (S305). Specifically, the controller 18 displays on the monitor whether the current operation mode is the heavy excavation mode or the light excavation mode.

[0111] Next, the controller 18 performs a key-off determination (S306) to determine whether the key switch of the engine is off (i.e., the crane 100 is stopped). If the key switch is not off (No in S306), the process returns to S301. On the other hand, if the key switch is off (Yes in S306), the controller 18 writes the set value of the brake control characteristic into the RAM (S307).

[0112] In this modification 1-3, the current operation mode (heavy excavation mode or light excavation mode) is written into the RAM upon turning off the key switch and the process is terminated. Therefore, when the key switch is turned on next time (i.e., the crane 100 starts to operate), the operation mode stored last time can be read as the initial value in S301. That is, the last operation mode can be automatically restored. Therefore, the control of the brake device 4 involved in modification 3 becomes a control that is more convenient for the operator to use.

[0113] <Second embodiment>

[0114] Figure 8 This is a hydraulic circuit diagram of the brake device 4 according to the second embodiment. Figure 8 The second embodiment shown is different from the first embodiment in that an electromagnetic proportional pressure reducing valve (hereinafter referred to as an electromagnetic proportional valve) 26 is provided on the upstream side of the brake mode switching valve 21, and a brake control characteristic adjustment dial 27 is connected to the controller 18. According to this structure, the hydraulic oil whose pressure is adjusted by the brake control valve 6 and the hydraulic oil whose pressure is adjusted by the electromagnetic proportional valve 26 are selectively supplied to the first pressure chamber 4m and the second pressure chamber 4n, so that the brake control characteristics can be changed more finely. The characteristics of the brake control characteristics in the second embodiment are described in detail below.

[0115] Fig. 9(a) is a diagram showing the control characteristics of the electromagnetic proportional valve. Fig. 9 (b) is a diagram showing the braking control characteristics in heavy excavation mode. Fig. 9 (c) is a diagram showing the braking control characteristics in the light excavation mode. Fig. 9 In (a), (b) and (c), the control characteristics when the brake control characteristic adjustment dial 27 is set to level 3 are represented by thick lines, and the control characteristics when the brake control characteristic adjustment dial 27 is set to level 1, level 2, level 4 and level 5 are represented by thin lines. Fig. 9 The control characteristics of each stage of the electromagnetic proportional valve 26 shown in (a) are stored in the storage device of the controller 18 in the form of a table.

[0116] In addition, Fig. 9 In (a), the characteristics of the control pressure of the electromagnetic proportional valve 26 relative to the pressure of the brake control valve 6 are specified, but the relationship between the depression amount (stroke) or depression force of the brake pedal 6a, or the rotation speed of the hoisting winch 105 and the characteristics of the control pressure of the electromagnetic proportional valve 26 may be specified instead of the pressure of the brake control valve 6. That is, the electromagnetic proportional valve 26 can be controlled by the controller 18 according to the control signal corresponding to the brake operation.

[0117] like Fig. 9 As shown in (a), the control characteristics of the electromagnetic proportional valve 26 when set to level 1 are as follows: when the pressure of the brake control valve 6 is in the range of greater than 0% and less than 20%, the control pressure of the electromagnetic proportional valve 26 increases linearly from 0% to 100% as the pressure increases; when the pressure of the brake control valve 6 is in the range of greater than 20% and less than 100%, the control pressure of the electromagnetic proportional valve 26 is maintained at 100%.

[0118] The control characteristics of the electromagnetic proportional valve 26 when set to level 2 are as follows: when the pressure of the brake control valve 6 is in the range of greater than 0% and less than 40%, the control pressure of the electromagnetic proportional valve 26 increases linearly from 0% to 100% as the pressure increases; when the pressure of the brake control valve 6 is in the range of greater than 40% and less than 100%, the control pressure of the electromagnetic proportional valve 26 is maintained at 100%.

[0119] The control characteristics of the electromagnetic proportional valve 26 when set to level 3 are as follows: when the pressure of the brake control valve 6 is greater than 0% and less than 60%, the control pressure of the electromagnetic proportional valve 26 increases linearly from 0% to 100% as the pressure increases; when the pressure of the brake control valve 6 is greater than 60% and less than 100%, the control pressure of the electromagnetic proportional valve 26 is maintained at 100%.

[0120] The control characteristics of the electromagnetic proportional valve 26 when set to level 4 are as follows: when the pressure of the brake control valve 6 is in the range of greater than 0% and less than 80%, the control pressure of the electromagnetic proportional valve 26 increases linearly from 0% to 100% as the pressure increases; when the pressure of the brake control valve 6 is in the range of greater than 80% and less than 100%, the control pressure of the electromagnetic proportional valve 26 is maintained at 100%.

[0121] The control characteristic of the electromagnetic proportional valve 26 when set to level 5 is as follows: within the range of the pressure of the brake control valve 6 from 0% to 100%, the control pressure of the electromagnetic proportional valve 26 increases linearly from 0% to 100% as the pressure increases.

[0122] In this way, the pressure of the electromagnetic proportional valve 26 is Fig. 9 The control characteristic shown in (a) is controlled, so in the heavy excavation mode, Fig. 9 The braking control characteristics shown in (b) can be obtained in light excavation mode. Fig. 9 The braking control characteristics are shown in (c).

[0123] For example, when the setting value of the brake control characteristic adjustment dial 27 is level 3, in the heavy excavation mode, Fig. 9 As shown in (b), the following braking control characteristics can be obtained: in the range of pedal stroke being greater than 0% and less than 40%, the braking force increases linearly with the increase in pedal stroke at the same slope as the characteristic based only on the first piston 4c, and in the range of pedal stroke being greater than 40% and less than 100%, an auxiliary characteristic based on the second piston 4d is added, and the braking force increases linearly at a steeper slope than the characteristic based only on the first piston 4c.

[0124] And, if Fig. 9 As shown in (c), in the light excavation mode, the following braking control characteristics can be obtained: even when the setting value is also level 3, in the range of pedal stroke being greater than 0% and less than 40%, the braking force increases linearly with the increase in pedal stroke at the same slope as the characteristic based only on the second piston 4d, and in the range of pedal stroke being greater than 40% and less than 100%, an auxiliary characteristic based on the first piston 4c is added, and the braking force increases linearly at a steeper slope than the characteristic based only on the second piston 4d.

[0125] Moreover, even in the same level 3, the slope of the straight line in the range of 0% to less than 40% of the pedal stroke is gentler in the heavy excavation mode than in the light excavation mode, and the slope of the straight line in the range of 40% to 100% of the pedal stroke is steeper.

[0126] Thus, in the second embodiment, since a more refined brake control characteristic can be realized, it becomes more convenient for the operator to use. In particular, the second embodiment is suitable for switching work between the heavy excavation mode and the light excavation mode.

[0127] Specifically, two to three winch devices are usually mounted on one crane 100. Therefore, the load form of each winch device may differ depending on the content of the work. For example, in clamshell bucket work, a winch device that supports the bucket and controls the lifting and lowering of the bucket and a winch device that controls the opening and closing of the bucket are used.

[0128] During excavation, when the bucket is allowed to freely fall in an expanded state (released state) and touch the ground, the bucket support winch device, which is under heavy load, adjusts the descending speed, and the bucket opening and closing winch device, which is under light load, follows the descending speed of the support winch device to close the bucket. If the following is delayed, the bucket will touch the ground in a closed state, while if the following is premature, the wire rope of the opening and closing winch device will loosen and may cause the rope to become tangled. Therefore, in the clamshell bucket operation, high operability is required for the bucket opening and closing winch device in particular.

[0129] As described above, the second embodiment is effective when the loads of the winch devices are different and differentiation is desired according to the load states.

[0130] In the above, the brake control characteristic adjustment dial 27 is set to five levels, namely, level 1 to level 5, but this setting is arbitrary. Furthermore, a continuously variable dial having intermediate values ​​between levels 1 to 5 may also be used.

[0131] (Variant 2-1)

[0132] Furthermore, the control characteristics of the electromagnetic proportional valve 26 according to the second embodiment may be modified to be curve controlled.

[0133] Fig.10 (a) is a diagram showing the control characteristics of the electromagnetic proportional valve. Fig.10 (b) is a diagram showing the braking control characteristics in heavy excavation mode. Fig.10 (c) is a diagram showing the braking control characteristics in the light excavation mode. Fig.10As shown in (a), the control characteristics of the electromagnetic proportional valve 26 when set to level 1 are as follows: within the range of the pressure of the brake control valve 6 being 0% or more and less than 20%, the control pressure of the electromagnetic proportional valve 26 increases from 0% to 100% as the pressure increases, and within the range of the pressure of the brake control valve 6 being 20% ​​or more and less than 100%, the control pressure of the electromagnetic proportional valve 26 is maintained at 100%. As for levels 2 to 5, as shown in the figure, they also have the following control characteristics: the control pressure of the electromagnetic proportional valve 26 increases with the increase of the pressure of the brake control valve 6.

[0134] In this way, the pressure of the electromagnetic proportional valve 26 is Fig.10 The control characteristic shown in (a) is controlled, so in the heavy excavation mode, Fig.10 The braking control characteristics shown in (b) can be obtained in light excavation mode. Fig.10 The braking control characteristics shown in (c) are shown in FIG.

[0135] For example, when the setting value of the brake control characteristic adjustment dial 27 is level 3, in the heavy excavation mode, Fig.10 As shown in (b), the following braking control characteristics can be obtained: in the range of 0% to less than 40% of the pedal stroke, the braking force increases linearly with the same slope as the characteristic based on the first piston 4c alone as the pedal stroke increases, and in the range of 40% to 100% of the pedal stroke, an auxiliary characteristic based on the second piston 4d is added, and the braking force increases in a curve as the pedal stroke increases. In addition, in the light excavation mode, the following braking control characteristics can be obtained: Fig.10 The braking control characteristics are shown in (c).

[0136] Modification 2-1 is preferred because it can achieve operability consistent with the operator's feeling when the braking energy accompanying free fall changes in a quadratic curve based on gravitational acceleration. In addition, if the second embodiment and modification 2-1 are set as a structure that can be selected by the operator, the performance will be further improved.

[0137] In addition, the present invention is not limited to the above-mentioned embodiments, and various changes can be made within the scope of the purpose of the present invention, and all technical matters included in the technical ideas recorded in the claims become the objects of the present invention. The above-mentioned embodiments are just preferred examples, and those skilled in the art can implement various alternative examples, modified examples, variations or improved examples according to the contents disclosed in this specification, which are all included in the technical scope recorded in the claims.

[0138] In the above-mentioned embodiments, the negative control type brake device 4 is exemplified, but a positive control type (positive) brake device may also be used. That is, in the present invention, the brake device is not limited to the negative control type.

[0139] Furthermore, although a crawler crane is shown as an example of a crane, the present invention is not limited thereto, and can be applied to other mobile cranes such as wheeled cranes, truck cranes, off-road tire cranes, and all-terrain cranes, as well as all cranes such as tower cranes, bridge cranes, jib cranes, luffing cranes, stacking cranes, gantry cranes, unloaders, and basic machinery such as earth-drilling machines. Furthermore, the present invention can also be applied to construction machinery other than cranes, such as road machinery or hydraulic excavators, wheel loaders, etc. Furthermore, the brake device of the present invention can also be applied to machinery other than winches.

Claims

1. A winch brake device, which is used for construction machinery and generates braking force according to a braking operation, characterized in that: have: A pressing member to press the brake members against each other to generate the braking force; a first brake cylinder including a first piston which is separate from the pressing member and capable of pressing the pressing member, wherein a first pressing force for pressing the brake members against each other is applied to the pressing member by the urging force of a first spring via the first piston; and The second brake cylinder includes a second piston which is separate from the pressing member and can press the pressing member independently of the first piston, and the second piston applies a second pressing force different from the first pressing force to the pressing member through the urging force of a second spring. supplying hydraulic oil to the first brake cylinder and the second brake cylinder, The pressing member is provided so as to contact the first piston of the first brake cylinder and the second piston of the second brake cylinder. The first brake cylinder and the second brake cylinder can each independently apply the first pressing force or the second pressing force.

2. The brake device of the winch according to claim 1, characterized in that: The first brake cylinder and the second brake cylinder can cooperatively apply the first pressing force and the second pressing force.

3. The brake device of the winch according to claim 1 or 2, characterized in that: The first brake cylinder has a first pressure chamber to which hydraulic oil is supplied. The second brake cylinder has a second pressure chamber to which hydraulic oil is supplied. One of the hydraulic oil of maximum pressure and the hydraulic oil whose pressure is adjusted according to the brake operation is selectively supplied to one of the first pressure chamber and the second pressure chamber, The other of the hydraulic oil at the maximum pressure and the hydraulic oil whose pressure is adjusted according to the brake operation is selectively supplied to the other of the first pressure chamber and the second pressure chamber.

4. The brake device of the winch according to claim 1 or 2, characterized in that: have: a brake control valve that operates in accordance with the brake operation; and The electromagnetic proportional valve works according to the input signal. The first brake cylinder has a first pressure chamber to which hydraulic oil is supplied. The second brake cylinder has a second pressure chamber to which hydraulic oil is supplied. The hydraulic oil whose pressure is adjusted by the brake control valve is supplied to one of the first pressure chamber and the second pressure chamber. The hydraulic oil whose pressure is adjusted by the electromagnetic proportional valve is applied to the other of the first pressure chamber and the second pressure chamber.

5. The brake device of the winch according to claim 4, characterized in that: The control characteristics of the electromagnetic proportional valve are pre-set to have multiple, The electromagnetic proportional valve operates according to the input signal corresponding to the control characteristic selected by the operator.

6. The brake device of a winch according to any one of claims 1 to 5, characterized in that: The construction machine is a crane capable of performing a free-fall operation in which a suspended object is lowered by its own weight. The crane is pre-set with the following operation modes as the operation modes in the free fall operation: a first operation mode in which the operation is performed by generating a braking force based on the first brake cylinder; and a second operation mode in which the operation is performed by generating a braking force based on the second brake cylinder. During the free fall operation, the switching of the operation mode is disabled.

7. The brake device of a winch according to any one of claims 1 to 5, characterized in that: The construction machine is a crane capable of performing a free-fall operation in which a suspended object is lowered by its own weight. The crane is pre-set with the following operation modes as the operation modes in the free fall operation: a first operation mode in which the operation is performed by generating a braking force based on the first brake cylinder; and a second operation mode in which the operation is performed by generating a braking force based on the second brake cylinder. The switching between the first operation mode and the second operation mode is automatically performed according to the load of the hanging object.

8. The brake device of the winch according to claim 4 or 5, characterized in that: The hydraulic oil supplied to the first pressure chamber and the hydraulic oil supplied to the second pressure chamber are supplied via the common brake control valve.

9. The brake device of a winch according to any one of claims 1 to 5, characterized in that: The first spring and the second spring have the same spring characteristics, but are different in number.

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