Winch brake device

Abstract

To provide a winch brake device capable of improving operability of free-fall work of a work machine.SOLUTION: A winch brake device (4) used for a work machine to generate a braking force on the basis of a brake operation comprises: a pressing member (4j) that presses brake members (4a and 4b) into contact with each other to generate the brake force; a first brake cylinder (31) that applies a first pressing force for pressing the brake members into contact with each other to the pressing member; and a second brake cylinder (32) that applies a second pressing force different from the first pressing force to the pressing member. The first and second brake cylinders can respectively apply the first and second pressing forces independently of each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a brake device for a winch used in a work machine. [Background technology]

[0002] As background art in this technical field, for example, Patent Document 1 describes a technology that can change the brake control characteristics when the crane is not in free fall and the braking characteristics when the crane is in free fall by arranging two brake mechanisms (brake cylinders) in series. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6645937 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because free fall operations occur in a variety of applications for cranes, braking characteristics that can accommodate the diversifying operations (various loads during operation) are required.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a winch brake device that can improve the operability of free fall work of a work machine (such as a crane). [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention is a winch brake device that is used in a work machine and generates a braking force based on a brake operation, the winch brake device including: a pressing member that presses braking members together to generate the braking force; a first piston configured separately from the pressing member and capable of pressing the pressing member; The pressing member Through the first piston a first brake cylinder that applies a first pressing force to bring the braking members into pressure contact with each other; a second piston configured separately from the pressing member and capable of pressing the pressing member independently of the first piston; The pressing member Through the second piston and a second brake cylinder that applies a second pressing force different from the first pressing force, wherein the first brake cylinder and the second brake cylinder are capable of applying the first pressing force or the second pressing force independently of each other.

[0007] According to the present invention, it is possible to improve the operability of the free fall operation of a work machine (such as a crane). 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 an external side view of a crane equipped with a brake device according to a first embodiment. [Diagram 2] FIG. 2 is a hydraulic circuit diagram of the brake device according to the first embodiment. [Diagram 3] 4A is a diagram showing the braking force characteristics of the first piston, FIG. 4B is a diagram showing the braking force characteristics of the second piston, FIG. 4C is a diagram showing the pressure characteristics of the brake control valve, and FIG. 4D is a diagram showing the brake control characteristics. [Figure 4] 4 is a flowchart showing a procedure of a control process of the brake device by a controller. [Diagram 5] FIG. 13 is a hydraulic circuit diagram of a brake device according to Modification 1-1. [Figure 6] 10 is a flowchart showing a procedure of a control process of a brake device according to Modification 1-2. [Figure 7] 10 is a flowchart showing a procedure of a control process of a brake device according to Modification 1-3. [Figure 8] FIG. 7 is a hydraulic circuit diagram of a brake device according to a second embodiment. [Figure 9] 1A is a diagram showing the control characteristics of an electromagnetic proportional valve, FIG. 1B is a diagram showing the brake control characteristics in a heavy excavation mode, and FIG. 1C is a diagram showing the brake control characteristics in a light excavation mode. [Figure 10]1A is a diagram showing the control characteristics of an electromagnetic proportional valve, FIG. 1B is a diagram showing the brake control characteristics in a heavy excavation mode, and FIG. 1C is a diagram showing the brake control characteristics in a light excavation mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which a brake device according to the present invention is applied to a crane, which is an example of a work machine, will be described with reference to the drawings.

[0010] First Embodiment 1 is an external side view of a crane equipped with a brake device according to the first embodiment. The crane 100 has a running body 101, a rotating body 103 that is rotatably mounted on the running body 101 via a rotating device 102, a boom 104 that is rotatably mounted on the rotating body 103 in the vertical direction, and a cab 108 in which an operator sits. The rotating body 103 is equipped with a hoisting winch 105 that is a winch for hoisting the boom, and a boom hoisting winch 106 that is a winch for raising and lowering the boom.

[0011] A hoisting rope 105a is wound around the hoisting winch 105. As the hoisting winch 105 rotates, the hoisting rope 105a is wound or unwound, and the hook 110 is raised and lowered via a sheave provided at the end of the boom 104. A hoisting rope 106a is wound around the hoisting winch 106. As the hoisting winch 106 rotates, the hoisting rope 106a is wound or unwound, and the boom 104 is raised and lowered via a sheave provided at the end of the boom 104.

[0012] The operator's cab 108 is provided with a hoisting operation lever 13 for operating the hoisting winch 105 to raise and lower the same, various operation levers (not shown) for operating the rotating body 103 and the hoisting winch 106 of the boom 104 to raise and lower the same, a controller 18 for controlling the crane 100, a brake mode changeover switch 17 for changing the operating mode of the brake device 4, a brake control characteristic changeover switch 24 for changing the control characteristics of the brake device 4, and a monitor (not shown) as an alarm means (see FIG. 2).

[0013] Fig. 2 is a hydraulic circuit diagram of the brake device according to the first embodiment of the present invention. Fig. 2 illustrates a hydraulic circuit for driving the hoisting winch 105, and does not illustrate a hydraulic circuit for driving the hoisting winch 106.

[0014] The crane 100 includes a controller 18 that controls the operation of each part of the crane 100, an engine (not shown), and a main pump 12, a cooling oil pump 19, and a pilot pump 9 that are driven by the engine (not shown). The main pump 12, the cooling oil pump 19, and the pilot pump 9 discharge the hydraulic oil in the tank 10 as pressurized oil.

[0015] Although not shown, the controller 18 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 18 is realized by the CPU loading various programs stored in the storage device into the RAM and executing them.

[0016] The hoisting winch 105 includes a winding 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 pressure oil to the hydraulic motor 1, driving the hydraulic motor 1 to drive the winding drum 3 to wind up and lower it. The control valve 11 controls the flow of pressure 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 winding drum 3. The brake device 4 brakes the carrier shaft 4g of the planetary reduction mechanism 2 to prevent the winding drum 3 from freely rotating.

[0017] The planetary reduction mechanism 2 includes a sun gear 2a, a planetary gear 2b, and a ring 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 is meshed with the planetary gear 2b, and the planetary gear 2b is meshed with a ring gear 2c provided on the inner periphery of the take-up drum 3. The planetary gear 2b is supported by a planetary carrier 2d. A carrier shaft 4g to which the planetary carrier 2d is fixed is supported by a bearing inside the brake device 4. The gap between the outer periphery of the carrier shaft 4g and a through hole through which the carrier shaft 4g is inserted is sealed by an oil seal 4h.

[0018] For ease of explanation, the direction of the rotation axis of the hoisting winch 105, i.e., the direction of the central axis of the carrier shaft 4g, will be simply referred to as the axial direction. In addition, of the two ends of the hoisting winch 105 in the axial direction, the side on which the output shaft of the hydraulic motor 1 is disposed will be referred to as the front side of the hoisting winch 105, and the opposite side in the axial direction will be referred to as the rear side of the hoisting winch 105.

[0019] (Brake device configuration) The brake device 4 also functions as a clutch device that transmits and interrupts rotation between the hydraulic motor 1 and the winding drum 3. In other words, the brake device 4 functions as a clutch and a parking brake during power winding and stopping, and as a service brake (service brake) during free fall. In this specification, the braking force required when the brake device 4 is used as a clutch is defined as the "required clutch force."

[0020] The brake device 4 applied to this embodiment is a negative type wet multi-plate brake having a plurality of friction plates 4a. The brake device 4 mainly includes a plurality of friction plates (braking members) 4a, a plurality of mating plates (braking members) 4b engaging with the plurality of friction plates 4a, a first brake cylinder 31, a second brake cylinder 32, a carrier shaft 4g, an oil seal 4h, and a pressing member 4j.

[0021] The multiple friction plates 4a are attached to the outer periphery of the carrier shaft 4g by spline connection so as to be movable in the axial direction but constrained in the rotational direction. On the other hand, the multiple counter plates 4b are arranged alternately with the multiple friction plates 4a in the axial direction and are attached to the inner periphery of the casing by spline connection so as to be free in the axial direction but constrained in the rotational direction. By applying a pressing force to the counter plates 4b, a friction torque generated between them and the friction plates 4a is transmitted to the carrier shaft 4g, generating a braking force.

[0022] The mating plates 4b are connected to each other by a spring. Therefore, in the brake released state, the mating plates 4b move away from each other, and a gap is formed between the friction plate 4a and the mating plate 4b. By forming a gap between the friction plate 4a and the mating plate 4b, drag torque (rotational resistance due to the viscosity of oil between the friction plate 4a and the mating plate 4b (so-called drag torque)) during free fall is reduced.

[0023] The first brake cylinder 31 has a first piston 4c, a plurality of springs (first springs) 4e that bias the first piston 4c, a first casing 4f that houses the first piston 4c, and a first pressure chamber 4m which is a ring-shaped space formed between the first casing 4f and the first piston 4c.

[0024] The second brake cylinder 32 has a second piston 4d, a plurality of springs (second springs) 4k that bias the second piston 4d, a second casing 4i that houses the second piston 4d, and a second pressure chamber 4n which is a ring-shaped space formed between the second casing 4i and the second piston 4d.

[0025] The first piston 4c is biased axially forward by a first pressing force by a plurality of springs 4e. The second piston 4d is disposed coaxially with the first piston 4c inside the first piston 4c. The second piston 4d is biased axially forward (to the right in FIG. 2) by a second pressing force by a plurality of springs 4k, similar to the first piston 4c. The first piston 4c and the second piston 4d can each independently press a pressing member 4j.

[0026] Here, the spring 4e biasing the first piston 4c and the spring 4k biasing 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 this embodiment, the springs 4e and 4k have the same spring characteristics (characteristics of deforming when force is applied and recovering when force is removed). Of course, the springs 4e and 4k may have nonlinear characteristics or different spring constants. Also, the number of springs 4e and 4k may be the same.

[0027] In this embodiment, the number of springs 4e biasing the first piston 4c is greater than the number of springs 4k biasing the second piston 4d, and more specifically, the ratio of the number of springs 4e to the number of springs 4e is 6:4. Therefore, the first piston 4c has a pressing force that presses the mating plate 4b 1.5 times greater than the second piston 4d. In other words, the first piston 4c can generate a braking force that is 1.5 times greater than the second piston 4d. The sum of the braking forces of the two brake cylinders 31 and 32 is set to be equal to the required clutch force. Therefore, the required clutch force is apportioned to the first brake cylinder 31 and the second brake cylinder 32 in a ratio of 6:4. In other words, the sum of the biasing forces of the springs 4e and 4k is equal to the pressing force required to generate the required clutch force.

[0028] The first pressure chamber 4m is supplied with pressure oil from a brake cylinder port B1. The second pressure chamber 4n is supplied with pressure oil from a brake cylinder port B2. When pressure oil is supplied to the first pressure chamber 4m, the first piston 4c is pressed axially rearward. When pressure oil is supplied to the second pressure chamber 4n, the second piston 4d is pressed axially rearward. Therefore, when the first piston 4c and the second piston 4d are pressed axially rearward, the braking force of the brake device 4 is smallest, and when the first piston 4c or the second piston 4d is pressed axially frontward, the braking force of the brake device 4 is largest.

[0029] The ratio (A1 / A2) of the pressure receiving area A1 of the pressure oil acting on the first pressure chamber 4m to the pressure receiving area A2 of the pressure oil acting on the second pressure chamber 4n is configured to be 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 this embodiment, since the ratio of the number of the springs 4e that bias the first piston 4c to the number of the springs 4k that bias the second piston 4d is 6:4, the ratio of the pressure receiving area A1 to the pressure receiving area A2 is also configured to be 6:4. This makes it possible to generate a braking force proportional to the depression amount of the brake pedal 6a. In other words, the ratio of the braking force proportional to the depression amount of the brake pedal 6a is also configured to be 6:4.

[0030] The relationship between the ratio of the pressing force of the first piston 4c and the pressing force of the second piston 4d and the ratio of the pressure receiving area A1 of the first pressure chamber 4m and the pressure receiving area A2 of the second pressure chamber 4n does not necessarily have to be the same. For example, the difference between the pressing force ratio and the pressure receiving area ratio may be within a range of ±10% (preferably within a range of ±5%). This includes cases where the effective pressure receiving areas in both pressure chambers 4m and 4n are actively adjusted to the required ratio, taking into account pressure loss due to piston seals attached to the brake cylinders 31 and 32.

[0031] The pressing member 4j is provided so as to be able to come into contact with the first piston 4c and the second piston 4d, and constantly presses the mating plate 4b by the biasing force of the spring 4e acting on the first piston 4c and the biasing force of the spring 4k acting on the second piston 4d. That is, the brake device 4 constantly generates a braking force (negative brake) by the axial forward pressing force acting on the pressing member 4j. Note that the shape of the pressing member 4j is not important as long as it can come into contact with the first piston 4c and the second piston 4d at the same time.

[0032] The brake cylinder port B1 is connected to the pilot pump 9 via the brake control valve 6, the brake mode changeover valve 5, and the brake control characteristics changeover valve 22, and is also connected to the pilot pump 9 via the brake mode changeover valve 21 and the brake control characteristics changeover valve 23. This allows the brake cylinder port B1 to selectively receive pressure oil whose pressure has been adjusted by the brake control valve 6 and pressure oil discharged from the pilot pump 9.

[0033] Similarly, the brake cylinder port B2 is connected to the pilot pump 9 via the brake control valve 6, the brake mode changeover valve 5, and the brake control characteristics changeover valve 22, and is also connected to the pilot pump 9 via the brake mode changeover valve 21 and the brake control characteristics changeover valve 23. This allows the brake cylinder port B2 to be selectively supplied with pressure oil whose pressure has been adjusted by the brake control valve 6 and pressure oil discharged from the pilot pump 9.

[0034] Here, in order to cool the braking device 4, cooling oil (pressurized oil) is forcibly circulated by a cooling oil pump 19. Specifically, the cooling oil discharged from the cooling oil pump 19 is supplied to the inside of the braking device 4 from the IN port, and after absorbing heat from the brake discs (friction plate 4a, mating plate 4b), 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 a casing internal pressure protection valve 20, which is a relief valve. Therefore, the internal pressure of the braking device 4 is also kept below the upper limit of the casing internal pressure protection valve 20. The positional relationship between the IN port and the OUT port may be configured inversely to that in this embodiment.

[0035] (Hydraulic circuit configuration) The hydraulic circuit that drives the hoisting winch 105 is provided with a motor brake changeover valve 7 that is change-over controlled by the operation of the hoisting operation lever 13, a motor brake cylinder 8, a brake control valve 6 that is operated by a brake pedal 6a, brake mode change-over valves 5, 21 and brake control characteristic change-over valves 22, 23 that are change-over controlled by a controller 18, and a casing internal pressure protection valve 20. Note that the brake control valve 6 may be configured to operate in response to a brake operation, and may be configured to operate in response to the depression amount of the brake pedal 6a, or may be configured to operate in response to the depression force of the brake pedal 6a, or may be configured to operate by replacing this operation with a manual operation, or may be configured to operate in response to the rotation speed of the hoisting winch 105.

[0036] In addition, in order to switch the operation mode (neutral brake mode / neutral free mode) of the brake device 4 by switching the brake mode switching valves 5, 21, a plurality of operation pressure sensors 15 and one brake circuit pressure sensor 16 are provided in this hydraulic circuit, each of which is connected to a controller 18. Furthermore, a brake mode switching switch 17 and a brake control characteristics switching switch 24 are connected to the controller 18.

[0037] The brake mode changeover switch 17 is a switch for selecting whether the operating mode is to be a neutral brake mode or a neutral free mode, which will be described later, and the brake control characteristic changeover switch 24 is a switch for selecting whether the work mode is to be a heavy excavation mode or a light excavation mode, which will be described later.

[0038] (Operation of hydraulic circuit) Next, the operation of the hydraulic circuit in the neutral brake mode, which is an operation mode for powered hoisting / lowering, and the operation of the hydraulic circuit in the neutral free mode, which is an operation mode for free fall, will be described. Figure 2 shows the state of the neutral brake mode. When the brake mode changeover switch 17 is switched to the operation position for the neutral brake mode, the brake mode changeover valves 5, 21 and the brake control characteristic changeover valves 22, 23 are in a non-excited state as shown in Figure 2. In this state, when the brake mode changeover switch 17 is switched to the operation position for the neutral free mode and other conditions are met, the brake mode changeover valves 5, 21 are excited and the operation mode is changed to the neutral free mode.

[0039] - Operation during powered lifting and lowering (neutral brake mode) - When the hoisting operation lever 13 shown in Fig. 2 is operated to the hoisting position or the lowering position, the pilot pressure from the pilot pump 9 acts on the control valve 11 to drive the spool of the control valve 11, and pressure oil discharged from the main pump 12 via 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 changeover valve 7 via the high pressure selection valve 14. As a result, the motor brake changeover 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, thereby driving the hydraulic motor 1 to rotate. The motor brake changeover valve 7 may be an electromagnetic changeover valve that is electrically switched by a detection signal from an operating pressure sensor 15.

[0040] In the neutral braking mode, the brake mode changeover valves 5, 21 and the brake control characteristics changeover valves 22, 23 are in a non-excited state. Therefore, the brake mode changeover valves 5, 21 are switched to positions (D1), (D2), respectively, and the brake control characteristics changeover valves 22, 23 are switched to positions (E1), (E2), respectively. Note that the brake control characteristics changeover valves 22, 23 do not necessarily have to be switched to positions (E1), (E2). In other words, the neutral braking mode may be started with the brake control characteristics changeover valves 22, 23 in positions (F1), (F2), respectively.

[0041] The pilot pressure from the pilot pump 9, which is the brake release pressure, is blocked by the brake mode changeover 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 are at tank pressure, the spring 4e urges the first piston 4c, and the spring 4k urges the second piston 4d. The urging forces of the springs 4e and 4k acting on the first piston 4c and the second piston 4d are transmitted to the pressing member 4j, which presses the mating plate 4b. As a result, the friction plate 4a and the mating plate 4b are pressed against each other, applying a braking force to the planetary carrier 2d and fixing the planetary carrier 2d.

[0042] In the neutral brake mode, when the sun gear 2a of the planetary reduction mechanism 2 rotates due to the rotational driving force of the hydraulic motor 1, the planetary gear 2b rotates on its axis, causing the ring gear 2c and the winding drum 3 connected to the ring gear 2c to rotate, thereby performing winding up or down by power.

[0043] -Free fall operation (neutral free mode)- When the hoisting operation lever 13 is operated to the neutral position, the control valve 11 cuts off the flow of pressure oil from the main pump 12 to the hydraulic motor 1. Pilot pressure oil is also no longer supplied to the motor brake changeover valve 7 via the high pressure selection valve 14, so the motor brake changeover valve 7 is switched to position (B). The motor brake changeover valve 7 cuts off the pilot pressure to the motor brake cylinder 8, so the motor brake is activated by the biasing force of the spring. In this state, when the brake mode changeover valves 5, 21 are excited and the braking force of the brake device 4 is released, the take-up drum 3 rotates freely due to the weight of the load suspended from the hook 110.

[0044] The mode is switched to the neutral free mode by operating the brake mode changeover valves 5, 21 by command of the controller 18 based on the respective determination values ​​of the operation pressure sensor 15, the brake circuit pressure sensor 16, and the brake mode changeover switch 17. For example, when it is detected that the brake mode changeover switch 17 has been switched to the operation position of the neutral free mode in a state in which the operation pressure detected by the operation pressure sensor 15 is smaller than a predetermined threshold value (i.e., the hoist operation lever 13 is in neutral) and the circuit pressure detected by the brake circuit pressure sensor 16 is smaller than a predetermined threshold value (i.e., the brake pedal 6a is depressed), the controller 18 switches the operation mode from the neutral brake mode to the neutral free mode.

[0045] Here, in this embodiment, a heavy excavation mode (first work mode) and a light excavation mode (second work mode) are prepared in advance as work modes in the neutral free mode. The heavy excavation mode is a mode suitable for dropping a heavy suspended load by its own weight (heavy load work), and the light excavation mode is a mode suitable for dropping a relatively light suspended load by its own weight (light load work). Specifically, the heavy excavation mode and the light excavation mode have different brake control characteristics, and are set so that the braking force in the heavy excavation mode is greater than that in the light excavation mode. The operation of the hydraulic circuit in each excavation mode will be described below.

[0046] -Heavy excavation mode- When the brake control characteristics changeover switch 24 is switched to the heavy excavation mode position, the work mode is changed over to the heavy excavation mode. In the heavy excavation mode, the brake mode changeover valves 5 and 21 are in an excited state, and the brake control characteristics changeover valves 22 and 23 are in a non-excited state. That is, in the heavy excavation mode, the brake mode changeover valves 5 and 21 are switched to positions (C1) and (C2), respectively, and the brake control characteristics changeover valves 22 and 23 are switched to positions (E1) and (E2), respectively.

[0047] Then, the brake mode switching valve 5 is subjected to pilot pressure adjusted by the brake control valve 6 (pilot pressure according to the depression amount of the brake pedal 6a), and the brake mode switching valve 21 is subjected directly to pilot pressure from the pilot pump 9, which is the brake release pressure (maximum pressure). 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 according to the difference between the biasing force of the spring 4e and the pilot pressure acting on the first pressure chamber 4m.

[0048] On the other hand, the pilot pressure (brake release pressure) from the pilot pump 9 acts directly 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 axially rearward (left side in FIG. 2) against the biasing force of the spring 4k, and the brake applied by the second piston 4d is released.

[0049] Thus, in the heavy excavation mode, the first brake cylinder 31 operates independently of the second brake cylinder 32, 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 that biases the first piston 4c.

[0050] -Light digging mode- When the brake control characteristics changeover switch 24 is switched to the light excavation mode position, the work mode is changed over to the light excavation mode. In the light excavation mode, the brake mode changeover valves 5, 21 are in an excited state, and the brake control characteristics changeover valves 22, 23 are in an excited state. That is, in the light excavation mode, the brake mode changeover valves 5, 21 are changed over to positions (C1), (C2), respectively, and the brake control characteristics changeover valves 22, 23 are changed over to positions (F1), (F2), respectively.

[0051] Then, the pilot pressure adjusted by the brake control valve 6 (pilot pressure according to the depression amount of the brake pedal 6a) is applied to the brake mode switching valve 5, and the pilot pressure from the pilot pump 9, which is the brake release pressure, 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 via the brake cylinder port B2. Therefore, the second piston 4d presses the pressing member 4j with a pressing force according to the difference between the biasing force of the spring 4k and the pilot pressure acting on the second pressure chamber 4n.

[0052] On the other hand, the pilot pressure (brake release pressure) from the pilot pump 9 acts directly 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 axially rearward (left side in FIG. 2) against the biasing force of the spring 4e, and the brake applied by the first piston 4c is released.

[0053] Thus, in the light excavation mode, the second brake cylinder 32 operates independently of the first brake cylinder 31, and only the second brake cylinder 32 generates a braking force. The braking force in the light excavation mode follows the spring characteristics of the spring 4k that biases the second piston 4d. In this way, by exciting the brake control characteristic changeover valves 22, 23, the brake cylinders 31, 32 that generate the braking force are selectively switched.

[0054] Next, various characteristics of the brake device 4 according to this embodiment will be described with reference to Fig. 3. Fig. 3(a) is a diagram showing the braking force characteristics of the first piston 4c, with the horizontal axis showing the pressure acting on the first pressure chamber 4m and the vertical axis showing the braking force by the first piston 4c. Fig. 3(b) is a diagram showing the braking force characteristics of the second piston 4d, with the horizontal axis showing the pressure acting on the second pressure chamber 4n and the vertical axis showing the braking force by the second piston 4d.

[0055] As described above, in this embodiment, the ratio of the number of springs 4e biasing the first piston 4c to the number of springs 4k biasing the second piston 4d is 6:4. If the required clutch force is 100% (maximum value of braking force), the braking force of the first piston 4c is a maximum of 60% of the required clutch force (see FIG. 3(a)), and the braking force of the second piston 4d is a maximum of 40% of the required clutch force (see FIG. 3(b)). Since the spring 4e has a linear characteristic, the braking force of the first piston 4c decreases linearly as the pressure acting on the first pressure chamber 4m increases. Similarly, the braking force of the second piston 4d also decreases linearly as the pressure acting on the second pressure chamber 4n increases.

[0056] The braking force characteristics of the first piston 4c and the second piston 4d can be adjusted by changing the spring characteristics of the springs 4e and 4k and the pressure-receiving areas of the first piston 4c and the second piston 4d.

[0057] 3(c) is a diagram showing the pressure characteristics of the brake control valve 6. The horizontal axis indicates the pedal stroke. The pedal stroke is expressed as a percentage of the pedal stroke (amount of depression), with the state in which the brake pedal 6a is fully depressed being 100% and the non-operated state in which the brake pedal 6a is not depressed being 0%.

[0058] 3(c), the pressure characteristic of the brake control valve 6 is such that the pressure decreases linearly with an increase in the pedal stroke in the range of 0% to 100%. Note that the pressure characteristic of the brake control valve 6 may not necessarily be such that the pressure decreases linearly with an increase in the pedal stroke.

[0059] FIG. 3(d) is a diagram showing brake control characteristics, with the horizontal axis showing pedal stroke and the vertical axis showing braking force. In FIG. 3(d), the required clutch force is set to 100%, and the braking force ratio is shown. As shown in FIG. 3(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. Then, when it is detected that the pedal stroke is 100%, the brake mode changeover valves 5, 21 are immediately de-energized, and the mode is temporarily switched to the neutral brake mode. Therefore, the first brake cylinder 31 and the second brake cylinder 32 work together to generate a braking force, which is the required clutch force (100%).

[0060] In this manner, in this embodiment, braking forces can be generated with different brake control characteristics in the heavy excavation mode and the light excavation mode when the pedal stroke is in the range of 0% to 100%.

[0061] Next, the control of the brake device 4 by the controller 18 will be described. Fig. 4 is a flowchart showing the procedure of the control process of the brake device 4 by the controller 18. As shown in Fig. 4, 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.

[0062] Next, the controller 18 performs a brake mode determination as to whether the current operation mode is the neutral brake mode or the neutral brake mode (S102). If the result of the brake mode determination is the neutral brake mode, the controller 18 performs an operation determination as to whether the brake control characteristics changeover switch 24 has been operated (S103). If the controller 18 determines, based on an input signal from the brake control characteristics changeover switch 24, that an operation to switch to the light excavation mode has been performed, it outputs a command to excite the brake control characteristics changeover valves 22, 23 (S104).

[0063] Here, in this embodiment, even if the mode is temporarily switched to the neutral brake mode during hoisting operation in S102, the mode can be switched to the light excavation mode or the heavy excavation mode by operating the brake control characteristics changeover switch 24, but when the mode is temporarily switched to the neutral brake mode, the work mode changeover may be prohibited or invalidated. In other words, the brake control characteristics changeover switch 24 may be valid only when the mode is permanently in the neutral brake mode.

[0064] Next, the controller 18 writes the setting value of the brake control characteristics (in this case, light excavation mode) to the RAM to update the setting value (S105). Next, the controller 18 displays the setting of the brake control characteristics on the monitor in the operator's cab 108 (S106). That is, the controller 18 displays on the monitor that the mode is heavy excavation mode or light excavation mode.

[0065] On the other hand, if the controller 18 determines in S103 that an operation to switch to the heavy excavation mode has been performed, it outputs a command to de-energize the brake control characteristic changeover valves 22, 23 (S107), and proceeds to S105.

[0066] Furthermore, in S102, if the result of the brake mode determination is the neutral free mode, the controller 18 performs an operation determination as to whether or not the brake control characteristics changeover switch 24 has been operated (S108), and if it is determined that it has been operated (S108 / YES), a warning is displayed on the monitor to the effect that the brake control characteristics cannot be changed (switching between heavy excavation mode and light excavation mode) (S109), and operation of the brake control characteristics changeover switch 24 is disabled. That is, switching between heavy excavation mode and light excavation mode is prohibited during the neutral free mode.

[0067] On the other hand, in S108, when the controller 18 determines that the brake control characteristic changeover switch 24 has not been operated (S108 / NO), the process ends.

[0068] According to the first embodiment configured as above, the following advantageous effects can be obtained.

[0069] 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. The braking characteristics of the first brake cylinder 31 and the braking characteristics of the second brake cylinder 32 are different (the number of springs 4e and the number of springs 4k are different). Therefore, the operator can operate the crane 100 while generating a braking force with 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 with the braking characteristics of the second brake cylinder 32. This improves the operability of the crane 100 during free fall work.

[0070] In particular, when the suspended load is heavy, the operator can select the heavy excavation mode to generate a braking force greater than that in the light excavation mode, enabling the brake pedal 6a to be operated in a manner that suits the operator's sense. Conversely, when the suspended load is light, the operator can select the light excavation mode to generate a braking force smaller than that in the heavy excavation mode even when the brake pedal 6a is depressed a predetermined amount, improving operability even in light load work. Thus, in this embodiment, even with a single brake device 4, one of two different brake characteristics can be selected according to the load of the suspended load, allowing free fall work to be performed favorably.

[0071] Furthermore, in the first embodiment, the brake characteristics of the brake device 4 are physically (mechanically) changed by switching between the first brake cylinder 31 and the second brake cylinder 32, and therefore the reliability is high. If the pressure of the pressurized oil acting on the first brake cylinder 31 and the second brake cylinder 32 were electrically controlled, there is a possibility that braking force will not be secured if electronic components fail, and this is unsuitable for a brake device that requires high safety. However, with the configuration of the first embodiment, such concerns are not present because the brake characteristics are switched physically (mechanically).

[0072] In addition, the heavy excavation mode and the light excavation mode are controlled so that they can be selected only during the neutral brake mode in the brake mode determination (S102). This improves the safety of the work. Specifically, since the suspended load falls under its own weight in the neutral free mode, if the operation mode is switched to the heavy excavation mode or the light excavation mode during this time, the brake characteristics are different, so the operator needs to adjust the amount of depression of the brake pedal 6a. Furthermore, due to the responsiveness at the time of switching the operation mode, the behavior of the hydraulic circuit may temporarily become unstable. In this respect, since the heavy excavation mode and the light excavation mode can be selected only during the neutral brake mode as in the present embodiment, there is an advantage that such a concern does not exist and the work can be performed safely.

[0073] During the neutral free mode, switching from heavy excavation mode to light excavation mode is prohibited, but switching from light excavation mode to heavy excavation mode is enabled, thereby ensuring safety while further improving operability for the operator.

[0074] Furthermore, since information on the heavy excavation mode, light excavation mode, various warning information, and the like are displayed on the monitor, the operator can easily visually recognize the operation mode, further improving the operability of the crane 100. Note that instead of displaying a warning on the monitor, a warning may be issued using a notification means such as a buzzer or lamp.

[0075] In the first embodiment, when it is detected that the pedal stroke is 100%, the brake mode switching valves 5, 21 are immediately de-energized to temporarily switch to the neutral brake mode, and a braking force equal to the required clutch force (100%) is generated. Therefore, the crane 100 can be safely operated. Of course, a configuration may be adopted in which a braking force lower than the required clutch force is generated when the pedal stroke is 100%.

[0076] Here, the brake device 4 according to the first embodiment can be modified in various ways as described below.

[0077] (Variation 1-1) Fig. 5 is a hydraulic circuit diagram of a brake device 4 according to Modification 1-1. Modification 1-1 shown in Fig. 5 is characterized in that, instead of providing the brake control characteristic changeover valves 22 and 23 shown in Fig. 2, a brake control characteristic changeover valve 25 that integrates the functions of the brake control characteristic changeover valves 22 and 23 is provided.

[0078] The brake control characteristics changeover valve 25 shown in Fig. 5 is in a non-excited state, and the brake control characteristics changeover valve 25 is switched to position (G2). When the brake mode changeover valves 5, 21 are excited in this state, 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. Then, a braking force is generated by the first brake cylinder 31 according to the depression amount of the brake pedal 6a. Therefore, when the brake control characteristics changeover valve 25 is in a non-excited state, the heavy excavation mode is selected.

[0079] On the other hand, when the operating mode is switched from the heavy excavation mode to the light excavation mode, the controller 18 outputs a command to excite the brake control characteristics changeover valve 25. Then, the brake control characteristics changeover valve 25 changes from position (G2) to position (G1). Then, 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. Then, a braking force is generated by the second brake cylinder 32 according to the depression amount of the brake pedal 6a.

[0080] In this way, the brake device 4 according to the modified example 1-1 also provides the same operational effects as those of the first embodiment. Moreover, the modified example 1-1 has an advantage that the hydraulic circuit configuration can be simplified since the number of brake control characteristic changeover valves is small.

[0081] (Variation 1-2) Fig. 6 is a flowchart showing the procedure of the control process of the brake device 4 according to the modified example 1-2. As shown in Fig. 6, 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). Next, 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).

[0082] If the result of the brake mode determination is the neutral free mode, the controller 18 performs a control characteristic determination to determine whether the set value of the brake control characteristic read in S201 is the heavy excavation mode or the light excavation mode (S203). If the controller 18 determines in S203 that it is the light excavation mode, it determines whether a hoisting operation has been performed (S204). Specifically, the controller 18 determines whether a hoisting operation has been performed by the hoisting operation lever 13 based on a detection signal input from the operation pressure sensor 15.

[0083] If the answer is YES in S204, the controller 18 detects the load (load of the suspended load) acting on the hoisting rope 105a with a load detector (not shown) and performs a descent allowable load determination as to whether or not to permit free fall of the suspended load based on the detected value (S205). If the detected value of the load detector is less than the threshold value, the controller 18 outputs a command to excite the brake control characteristic changeover valves 22, 23 (S206).

[0084] On the other hand, if the detected value of the load detector is equal to or greater than the threshold value, the controller 18 displays a warning on the monitor to indicate that the mode will be changed to heavy excavation mode (S207). Next, the controller 18 outputs a command to de-energize the brake control characteristic changeover valves 22, 23 (S208) and writes the set value of the brake control characteristic to the RAM (S209). In this case, the heavy excavation mode is written to the RAM. Then, 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.

[0085] In addition, if it is determined in S202 that the neutral brake mode is selected, if it is determined in S203 that the heavy excavation mode is selected, or if it is determined in S204 that the hoisting operation is not being performed (S204 / NO), the controller 18 ends the processing.

[0086] In this variant 1-2, when the current operating mode is the neutral free mode and the light excavation mode, the operation of the hoisting operation lever 13 and the load of the suspended load acting on the hoisting rope 105a are detected (S204, S205), and if the load of the suspended load is less than a threshold value, the light excavation mode is continued and the brake control characteristics changeover valves 22, 23 are excited (S206), and if the load of the suspended load is equal to or greater than the threshold value, the brake control characteristics changeover valves 22, 23 are automatically de-excited and the mode is switched to heavy excavation mode (S208), which is easy for the operator to use and also has excellent safety.

[0087] In addition, in the modified example 1-2, the controller 18 may store the state where the mode is automatically switched to the heavy excavation mode in S208 in the RAM and may reflect the state in the next hoisting operation, or may perform processing limited to the current hoisting operation. Also, the load of the suspended load may be detected by a device other than the load detector.

[0088] (Variation 1-3) FIG. 7 is a flowchart showing the procedure of the control process of the brake device 4 according to the modified example 1-3. As shown in FIG. 7, first, the controller 18 reads the current brake control characteristic setting value (heavy excavation mode or light excavation mode) stored in the RAM (S301), and performs a control characteristic determination to determine whether the read brake control characteristic setting value is the heavy excavation mode or the light excavation mode (S302). If the controller 18 determines in S302 that the mode is the light excavation mode, it outputs a command to excite the brake control characteristic switching valves 22, 23 (S303). On the other hand, if the controller 18 determines in S302 that the mode is the heavy excavation mode, it outputs a command to de-excite the brake control characteristic switching valves 22, 23 (S304). Then, the controller 18 displays the current brake control characteristic on the monitor (S305). Specifically, the controller 18 displays on the monitor that the current operation mode is the heavy excavation mode or the light excavation mode.

[0089] Next, the controller 18 performs a key-off determination to determine whether or not the engine key switch is turned off (i.e., the operation of the crane 100 is stopped) (S306). If the key switch is not turned off (S306 / NO), the process returns to S301. On the other hand, if the key switch is turned off (S306 / YES), the controller 18 writes the setting value of the brake control characteristic to the RAM (S307).

[0090] In this modification 1-3, when the key switch is turned OFF, the current work mode (heavy excavation mode or light excavation mode) is written to RAM and processing ends, so that the next time the key switch is turned ON (i.e., when the crane 100 starts operating), the work mode previously stored in S301 can be read as the initial value. In other words, the previous work mode can be automatically restored. Therefore, the control of the brake device 4 according to modification 3 is even more user-friendly for the operator.

[0091] <Second embodiment> Fig. 8 is a hydraulic circuit diagram of the brake device 4 according to the second embodiment. The second embodiment shown in Fig. 8 differs from the first embodiment in that an electromagnetic proportional pressure reducing valve (hereinafter referred to as an electromagnetic proportional valve) 26 is provided upstream of the brake mode switching valve 21, and a brake control characteristic adjustment dial 27 is connected to the controller 18. According to this configuration, pressure oil whose pressure is adjusted by the brake control valve 6 and pressure 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 characteristic can be varied more finely. Below, the features of the brake control characteristic in the second embodiment will be specifically described.

[0092] Fig. 9(a) is a diagram showing the control characteristics of the solenoid proportional valve, (b) is a diagram showing the brake control characteristics in heavy excavation mode, and (c) is a diagram showing the brake control characteristics in light excavation mode. In Fig. 9(a), (b), and (c), the control characteristics when the brake control characteristics adjustment dial 27 is set to level 3 are shown by thick lines, and the control characteristics of levels 1, 2, 4, and 5 are shown by thin lines. The control characteristics for each level of the solenoid proportional valve 26 shown in Fig. 9(a) are stored in the storage device of the controller 18 in the form of a look-up table.

[0093] 9(a) specifies the characteristics of the control pressure of the electromagnetic proportional valve 26 relative to the pressure of the brake control valve 6, but instead of the pressure of the brake control valve 6, it is also possible to specify 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. In other words, the electromagnetic proportional valve 26 may be configured to be operated by the controller 18 based on a control signal corresponding to the brake operation.

[0094] As shown in FIG. 9(a), the control characteristic of the solenoid proportional valve 26 when set to level 1 is such that when the pressure of the brake control valve 6 is in the range of 0% or more and less than 20%, the control pressure of the solenoid proportional valve 26 increases linearly from 0% to 100% in response to an increase in pressure, and when the pressure of the brake control valve 6 is in the range of 20% or more and 100% or less, the control pressure of the solenoid proportional valve 26 is maintained at 100%.

[0095] The control characteristics of the solenoid proportional valve 26 when set to level 2 are such that when the pressure of the brake control valve 6 is in the range of 0% or more and less than 40%, the control pressure of the solenoid proportional valve 26 increases linearly from 0% to 100% in response to an increase in pressure, and when the pressure of the brake control valve 6 is in the range of 40% or more and 100% or less, the control pressure of the solenoid proportional valve 26 is maintained at 100%.

[0096] The control characteristic of the solenoid proportional valve 26 when set to level 3 is such that when the pressure of the brake control valve 6 is in the range of 0% or more and less than 60%, the control pressure of the solenoid proportional valve 26 increases linearly from 0% to 100% in response to an increase in pressure, and when the pressure of the brake control valve 6 is in the range of 60% or more and 100% or less, the control pressure of the solenoid proportional valve 26 is maintained at 100%.

[0097] The control characteristics of the solenoid proportional valve 26 when set to level 4 are such that when the pressure of the brake control valve 6 is in the range of 0% or more and less than 80%, the control pressure of the solenoid proportional valve 26 increases linearly from 0% to 100% in response to an increase in pressure, and when the pressure of the brake control valve 6 is in the range of 80% or more and 100% or less, the control pressure of the solenoid proportional valve 26 is maintained at 100%.

[0098] The control characteristic of the solenoid proportional valve 26 when set to level 5 is such that, when the pressure of the brake control valve 6 is in the range of 0% or more and 100% or less, the control pressure of the solenoid proportional valve 26 increases linearly from 0% to 100% in response to an increase in pressure.

[0099] In this way, the pressure of the electromagnetic proportional valve 26 is controlled according to the control characteristics shown in Figure 9(a), so that in the heavy excavation mode, the brake control characteristics shown in Figure 9(b) are obtained, and in the light excavation mode, the brake control characteristics shown in Figure 9(c) are obtained.

[0100] For example, when the setting value of the brake control characteristic adjustment dial 27 is at level 3, in heavy excavation mode, as shown in FIG. 9(b), in the range of pedal stroke between 0% and less than 40%, the braking force increases linearly with increasing pedal stroke at the same slope as the characteristic due to the first piston 4c alone, and in the range of pedal stroke between 40% and 100%, the assist characteristic due to the second piston 4d is added, resulting in a brake control characteristic in which the braking force increases linearly at a steeper slope than the characteristic due to the first piston 4c alone.

[0101] Furthermore, as shown in FIG. 9(c), in the light excavation mode, even when the setting value is the same level 3, when the pedal stroke is in the range of 0% or more and less than 40%, the braking force increases linearly with an increase in pedal stroke at the same slope as the characteristic due to the second piston 4d alone, and when the pedal stroke is in the range of 40% or more and less than 100%, the assist characteristic due to the first piston 4c is added, resulting in a brake control characteristic in which the braking force increases linearly at a steeper slope than the characteristic due to the second piston 4d alone.

[0102] Even at the same level 3, the slope of the straight line in the heavy digging mode is gentler in the pedal stroke range of 0% or more and less than 40% than in the light digging mode, and the slope of the straight line in the pedal stroke range of 40% or more and less than 100 is steeper.

[0103] In this way, in the second embodiment, more detailed brake control characteristics can be realized, which makes it even easier for the operator to use. In particular, the second embodiment is suitable for work in which the heavy excavation mode and the light excavation mode are switched.

[0104] Specifically, one crane 100 is usually equipped with two to three winch devices. Therefore, the load pattern of each winch device may differ depending on the work content. For example, in clamshell work, a winch device that supports a 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.

[0105] During excavation, when the bucket is in an open (released) state and the bucket is landed on the ground by free fall operation, the descent speed is adjusted by the winch device for supporting the bucket, which is a heavy load, and the winch device for opening and closing the bucket, which is a light load, is operated to close the bucket by following the descent speed of the support winch device. If the follow-up is delayed, the bucket will land after it is closed, but if the follow-up is ahead, the wire rope of the winch device for opening and closing may become loose and become untidy. For this reason, high operability is required especially for the winch device for opening and closing the bucket, in clamshell work.

[0106] In this way, the load differs for each winch device, and the second embodiment is effective when it is desired to specialize for each load type.

[0107] Although the brake control characteristic adjustment dial 27 is set to five levels, 1 to 5, this setting is arbitrary. Also, a continuously variable dial having intermediate values ​​between 1 to 5 levels may be used.

[0108] (Variation 2-1) Moreover, the control characteristics of the proportional solenoid valve 26 according to the second embodiment can be modified so as to be controlled in a curved manner.

[0109] Fig. 10(a) is a diagram showing the control characteristics of the solenoid proportional valve, (b) is a diagram showing the brake control characteristics in the heavy excavation mode, and (c) is a diagram showing the brake control characteristics in the light excavation mode. As shown in Fig. 10(a), the control characteristics of the solenoid proportional valve 26 when set to level 1 are such that when the pressure of the brake control valve 6 is in the range of 0% or more and less than 20%, the control pressure of the solenoid proportional valve 26 increases in a curved manner from 0% to 100% in response to an increase in pressure, and when the pressure of the brake control valve 6 is in the range of 20% or more and 100% or less, the control pressure of the solenoid proportional valve 26 is maintained at 100%. As shown in the figure, the control characteristics of levels 2 to 5 are also such that the control pressure of the solenoid proportional valve 26 increases in a curved manner as the pressure of the brake control valve 6 increases.

[0110] In this way, the pressure of the electromagnetic proportional valve 26 is controlled according to the control characteristics shown in Figure 10(a), so that in the heavy excavation mode, the brake control characteristics shown in Figure 10(b) are obtained, and in the light excavation mode, the brake control characteristics shown in Figure 10(c) are obtained.

[0111] For example, when the setting value of the brake control characteristic adjustment dial 27 is at level 3, in heavy excavation mode, in the pedal stroke range of 0% or more and less than 40%, the braking force increases linearly with the same slope as the characteristic due to only the first piston 4c as the pedal stroke increases, and in the pedal stroke range of 40% or more and less than 100%, the assist characteristic due to the second piston 4d is added, resulting in a brake control characteristic in which the braking force increases curvilinearly as the pedal stroke increases. Also in light excavation mode, a brake control characteristic such as that shown in Figure 10(c) is obtained.

[0112] Modification 2-1 is preferable because it can realize operability that matches the operator's sense when the braking energy accompanying the free descent changes quadratically due to the gravitational acceleration. Furthermore, it is more functional if the second embodiment and modification 2-1 are configured so that the operator can select.

[0113] 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.

[0114] In the above-described embodiments, the negative type brake device 4 is exemplified, but a positive type brake device may be used. That is, in the present invention, the brake device is not limited to the negative type.

[0115] Furthermore, 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 other mobile cranes such as wheel cranes, truck cranes, rough terrain cranes, and all-terrain cranes, as well as tower cranes, overhead cranes, jib cranes, retractable cranes, stacker cranes, gantry cranes, unloaders, and foundation machines such as earth drills. The present invention can also be applied to work machines other than cranes, such as road machinery, hydraulic excavators, and wheel loaders. The brake device of the present invention can also be applied to machines other than winches. [Explanation of symbols]

[0116] 1 Hydraulic motor 2 Planetary reduction mechanism 2a Sun gear 2b Planetary Gear 2c Ring gear 2d Planetary Carrier 3 Winding drum 4 Brake device 4a Friction plate (braking member) 4b Counter plate (braking member) 4c First piston 4d 2nd piston 4e Spring (first spring) 4f First casing 4g carrier axis 4h Oil seal 4i Second casing 4j Pressing member 4k spring (second spring) 4m First Pressure Chamber 4n Second pressure chamber 5 Brake mode change 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 Winding operation lever 15 Operating pressure sensor 16 Brake circuit pressure sensor 17 Brake mode switch 18 Controller 19 Cooling oil pump 20 Casing internal pressure protection valve 21 Brake mode change valve 22 Brake control characteristic changeover valve 23 Brake control characteristic changeover valve 24 Brake control characteristics changeover switch 25 Brake control characteristic changeover valve 26 Solenoid proportional pressure reducing valve (Solenoid proportional valve) 27 Brake control characteristics adjustment dial 31 No. 1 brake cylinder 32 No. 2 brake cylinder 100 Crane 101 Vehicle 102 Swivel 103 Rotating body 104 Boom 108 Cab 105 Hoisting winch (winch) 106 Hoisting winch (winch) 105a Winding Rope 110 Hook 106a Descending rope B1 Brake cylinder port B2 Brake cylinder port

Claims

1. A winch brake device used in a work machine that generates a braking force based on a brake operation, a pressing member that presses the braking members together to generate the braking force; a first brake cylinder including a first piston configured separately from the pressing member and capable of pressing the pressing member, and applying a first pressing force to the pressing member via the first piston for pressing the braking members together; a second piston configured separately from the pressing member and capable of pressing the pressing member independently of the first piston, and a second brake cylinder applying a second pressing force different from the first pressing force to the pressing member via the second piston, A winch braking device, characterized in that the first brake cylinder and the second brake cylinder are capable of applying the first pressing force or the second pressing force independently of each other.

2. 2. The winch brake device according to claim 1, A winch braking device, characterized in that the first brake cylinder and the second brake cylinder are capable of applying the first pressing force and the second pressing force in cooperation with each other.

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

4. The winch brake device according to claim 1 or 2, a brake control valve that operates in response to the brake operation; a proportional solenoid valve that operates based on an input signal; the first brake cylinder has a first pressure chamber to which pressure oil is supplied, the second brake cylinder has a second pressure chamber to which pressure oil is supplied, One of the first pressure chamber and the second pressure chamber is supplied with pressure oil whose pressure is adjusted by the brake control valve, a brake device for a winch, wherein the other of the first pressure chamber and the second pressure chamber is supplied with pressurized oil whose pressure is adjusted by the electromagnetic proportional valve.

5. 5. The winch brake device according to claim 4, A plurality of control characteristics of the solenoid proportional valve are set in advance, 13. A winch brake device, comprising: a proportional solenoid valve operable based on an input signal corresponding to the control characteristic selected by an operator.

6. In the winch brake device according to any one of claims 1 to 5, The work machine is a crane capable of performing a free fall operation in which a suspended load is dropped by its own weight, The crane has the following working modes in the free fall work: a first working mode in which work is performed by generating a braking force by the first brake cylinder; a second operation mode in which work is performed by generating a braking force by the second brake cylinder; A winch brake device, characterized in that the switching of the work mode is disabled during the free fall work.

7. In the winch brake device according to any one of claims 1 to 5, The work machine is a crane capable of performing a free fall operation in which a suspended load is dropped by its own weight, The crane has the following working modes in the free fall work: a first working mode in which work is performed by generating a braking force by the first brake cylinder; a second operation mode in which work is performed by generating a braking force by the second brake cylinder; A winch brake device, characterized in that switching between the first operation mode and the second operation mode is performed automatically based on the load of the suspended load.

8. The winch brake device according to claim 4 or 5, 2. A brake device for a winch, wherein the pressure oil supplied to the first pressure chamber and the pressure oil supplied to the second pressure chamber are supplied via a common brake control valve.

9. In the winch brake device according to any one of claims 1 to 5, the first brake cylinder applies the first pressing force to the pressing member by a biasing force of a first spring, the second brake cylinder applies the second pressing force to the pressing member by a biasing force of a second spring, A winch brake device, wherein the first spring and the second spring have the same spring characteristics but are different in number from each other.

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