Brake control device and crane equipped with the same

Abstract

To provide a brake control device which can inhibit a brake response time from increasing when rapid brake operation is conducted, and to provide a crane including the brake control device.SOLUTION: A brake control device 10 includes: a hydraulic pump 22; a brake unit 6 which generates brake force exerted on a winch drum 11; an operation device 7 to which brake operation is provided; an electromagnetic proportional pressure reduction valve 2 which opens or closes so that a pressure of working fluid to be supplied to the brake unit 6 can be adjusted according to a control amount of the brake operation; selector valves 1, 12 disposed between the hydraulic pump 22 and the brake unit 6; and a controller 4 which switches the selector valves 1, 12 so that the brake unit 6 detours the electromagnetic proportional pressure reduction valve 2 and is connected to the hydraulic pump 22 when conditions of determination for determining that rapid brake operation is provided to the operation device are met.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a brake control device and a crane including the same.

Background Art

[0002] Generally, a crane includes a self-propelled lower traveling body, an upper slewing body rotatably supported by the lower traveling body, a boom member attached to the upper slewing body so as to be able to move up and down, a hook suspended from the tip of the boom member via a rope, and a winch for winding and unwinding the rope.

[0003] Patent Document 1 discloses a winch control device that controls the operation of a winch. This winch control device includes a winch, a state switching valve (state switching unit), a pressure control valve, and a brake force adjustment unit. The pressure control valve is a valve that converts a command from the brake force adjustment unit into hydraulic pressure. The pressure control valve is a valve that controls (adjusts) the brake force when the winch is in a free state (when the switching position of the state switching valve is in the free position). The pressure control valve is, for example, an electromagnetic proportional pressure reducing valve. The winch includes a winch drum, a motor, a speed reducer, and a clutch.

[0004] The clutch switches the connection state (degree of connection) between the motor and the winch drum. The clutch applies a brake to the rotation of the winch drum. The clutch includes a housing, a clutch plate, a clutch cylinder, and a spring. The clutch cylinder includes a piston capable of pressing the clutch plate, a pressure contact chamber, and a separation chamber. In response to a command from the brake force adjustment unit, the opening degree of the pressure control valve changes, and the pressure in the pressure contact chamber changes. The brake force of the winch (clutch) changes according to the pressure in the pressure contact chamber.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when the pressure control valve is an electromagnetic proportional pressure reducing valve, due to its structure, the electromagnetic proportional pressure reducing valve is good at controlling static pressure, but may not necessarily be suitable for operations that supply a large flow rate. Also, in order to ensure sufficient braking capacity in the clutch (brake unit), the pressure receiving areas of the pressure contact chamber and the separation chamber, the stroke of the piston, and the piston volume (the product of the pressure receiving area and the stroke) increase. Therefore, when an emergency braking operation is performed by the operator, the flow rate of the hydraulic oil required in the brake unit (the value obtained by dividing the piston volume by the brake response time) increases. However, in the flow rate control by the pressure control valve constituted by the electromagnetic proportional pressure reducing valve, the flow rate of the hydraulic oil required in the brake unit may not be quickly supplied to the brake unit when an emergency braking operation is performed. In this case, the brake response time may become long.

Means for Solving the Problems

[0007] An object of the present disclosure is to provide a brake control device capable of suppressing an increase in the brake response time when an emergency braking operation is performed, and a crane equipped with the same.

[0008] The provided brake control device includes a hydraulic pump, a brake unit capable of generating a braking force on a winch drum in response to the supply of hydraulic oil discharged from the hydraulic pump, an operating device to which a brake operation for adjusting the braking force is applied, an electromagnetic proportional pressure reducing valve that opens and closes so that the pressure of the hydraulic oil supplied to the brake unit is adjusted according to the operation amount of the brake operation, a switching valve interposed between the hydraulic pump and the brake unit, and a controller that switches the switching valve so that when a preset determination condition for determining that an emergency brake operation has been applied to the operating device is satisfied, the brake unit bypasses the electromagnetic proportional pressure reducing valve and is connected to the hydraulic pump.

[0009] In this brake control device, when the determination condition is satisfied, the controller controls the operation of the switching valve so that the brake unit bypasses the electromagnetic proportional pressure reducing valve and is connected to the hydraulic pump (that is, the hydraulic pump and the brake unit are connected without passing through the electromagnetic proportional pressure reducing valve). Therefore, when an emergency brake operation is applied to the operating device, the secondary pressure of the hydraulic pump is quickly transmitted to the brake unit. Accordingly, in this brake control device, a large flow rate of hydraulic oil can be quickly supplied to the brake unit without being affected by the electromagnetic proportional pressure reducing valve in terms of time when an emergency brake operation is performed. As a result, it is possible to suppress an increase in the brake response time when an emergency brake operation is performed.

[0010] Preferably, the determination condition includes that the operation amount of the brake operation exceeds an operation amount threshold which is a preset threshold value. The operation amount in an emergency brake operation usually tends to be the maximum operation amount that can be applied to the operating device or a large operation amount close thereto. Therefore, in this configuration, the controller can determine whether an emergency brake operation has been applied to the operating device by comparing the operation amount of the brake operation with the operation amount threshold.

[0011] Preferably, the determination condition includes that the operation speed of the braking operation exceeds an operation speed threshold value which is a preset value. In an emergency braking operation, the operation speed usually tends to be high. Therefore, with this configuration, the controller can determine whether an emergency braking operation has been applied to the operating device by comparing the operation speed of the braking operation with the operation speed threshold value.

[0012] The braking control device further includes a mode switching valve for switching between a free mode and a braking mode. The switching valve is a second switching valve arranged in parallel with the mode switching valve between the hydraulic pump and the brake unit. The second switching valve may be an electromagnetic switching valve with higher responsiveness to a command signal from the controller than the mode switching valve. With this configuration, by arranging the two switching valves (the mode switching valve and the second switching valve) in parallel in the hydraulic circuit, the switching operation between the free mode and the braking mode by the mode switching valve and the rapid response during emergency braking can be performed more smoothly.

[0013] The provided crane includes a machine body, a lifting member attached to the machine body so as to be able to lift and lower, a winch drum for winding and unwinding a rope hanging from the lifting member, and the above-described braking control device capable of adjusting the braking force on the winch drum. With this crane, it is possible to suppress an increase in the brake response time when an emergency braking operation is performed.

Advantages of the Invention

[0014] According to the present disclosure, there are provided a braking control device capable of suppressing an increase in the brake response time when an emergency braking operation is performed, and a crane equipped with the same.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0017] FIG. 1 is a side view showing a crane 100 according to an embodiment of the present disclosure. As shown in FIG. 1, the crane 100 includes a self-propelled lower traveling body 101, an upper slewing body 103 rotatably supported on the lower traveling body 101 about an axis, a lifting member attached to the upper slewing body 103 so as to be able to rise and fall, a hook 105 suspended from the tip of the lifting member via a rope R, a gantry 107 attached to the upper slewing body 103, and a winch drum 11. The lower traveling body 101 and the upper slewing body 103 are examples of the machine body. In the crane 100 shown in FIG. 1, the lifting member is constituted by a boom 104, but the lifting member may further include a jib (not shown) attached to the tip of the boom 104. Further, the crane 100 may be provided with a mast instead of the gantry 107.

[0018] The winch drum 11 causes the hook 105 to perform a lifting and lowering operation for lifting work by winding or unwinding the rope R connected to the hook 105. The rope R is fed out from the winch drum 11, passes through the tip of the undulating member, and is arranged to hang down from the tip of the undulating member to suspend the hook 105. A suspended load 106 is suspended from the hook 105. The winch drum 11 is arranged such that its rotation axis coincides with the width direction of the upper slewing body 103. In the present embodiment, the winch drum 11 is supported by the upper slewing body 103, but it may be supported by the boom 104.

[0019] As shown in FIG. 2, the crane 100 further includes a main pump 21, a winch motor 23, a winch control valve 24, a winch operating device 25, and a speed reducer 28.

[0020] The main pump 21 discharges hydraulic oil by being driven by a drive source (not shown) such as an engine.

[0021] The winch motor 23 is a hydraulic motor for rotationally driving the winch drum 11. In the present embodiment, the winch motor 23 has an output shaft 23a that rotates by receiving the supply of hydraulic oil from the main pump 21. The winch motor 23 has a first port and a second port, and when it receives the supply of hydraulic oil to one of these ports, the output shaft 23a rotates in the direction corresponding to the one port and discharges hydraulic oil from the other port.

[0022] The winch control valve 24 is interposed between the main pump 21 and the winch motor 23, selectively guides the hydraulic oil for driving the winch motor 23 from the main pump 21 to one of the first port and the second port of the winch motor 23 to control the direction of the hydraulic oil supplied to the winch motor 23, and controls the flow rate of the hydraulic oil supplied to the winch motor 23. The winch control valve 24 has a first pilot port and a second pilot port.

[0023] The winch operation device 25 has a winch operation lever 25a and a pilot valve 25b (remote control valve). The winch operation lever 25a rotates in the direction in which a winch operation is applied to the winch operation lever 25a by an operator. The pilot valve 25b has an inlet port connected to a pilot pump (not shown) and a pair of outlet ports. The pair of outlet ports are respectively connected to the first pilot port and the second pilot port of the winch control valve 24 via pilot lines. The pilot valve 25b opens to allow a pilot pressure corresponding to the magnitude of the winch operation to be supplied from the pilot pump to the pilot port corresponding to the direction of the winch operation applied to the winch operation lever 25a among the first and second pilot ports. Note that the pilot pump may be a control pump 22 described later, or may be a pump different from the control pump 22.

[0024] When no pilot pressure is input to either the first or second pilot port, the winch control valve 24 is held in the neutral position (the central position in Fig. 2). In this neutral position, the connection between the main pump 21 and the winch motor 23 is blocked and the center bypass line is opened, so that the hydraulic oil from the main pump 21 returns directly to the tank 27 through the center bypass line.

[0025] When a pilot pressure equal to or higher than a certain level is supplied to the first pilot port, the winch control valve 24 shifts from the neutral position to the first drive position (the upper position in Fig. 2) with a stroke corresponding to the magnitude of the pilot pressure. In this first drive position, the hydraulic oil from the main pump 21 is supplied to the first port of the winch motor 23 at a flow rate corresponding to the stroke, and the hydraulic oil is discharged from the second port. As a result, the output shaft 23a of the winch motor 23 rotates in the first direction. The discharged hydraulic oil returns to the tank 27.

[0026] When a pilot pressure equal to or higher than a certain level is supplied to the second pilot port, the winch control valve 24 shifts from the neutral position to the second drive position (the lower position in Fig. 2) with a stroke corresponding to the magnitude of the pilot pressure. At this second drive position, the hydraulic oil from the main pump 21 is supplied to the second port of the winch motor 23 at a flow rate corresponding to the stroke, and the hydraulic oil is discharged from the first port. As a result, the output shaft 23a of the winch motor 23 rotates in the second direction. The discharged hydraulic oil returns to the tank 27.

[0027] The speed reducer 28 is provided between the output shaft 23a of the winch motor 23 and the winch drum 11 to transmit the power of the winch motor 23 to the winch drum 11. The speed reducer 28 is constituted by, for example, a planetary gear mechanism. A plate 6e in the brake unit 6 described later is connected to the carrier shaft of the speed reducer 28.

[0028] The crane 100 is provided with a brake control device 10. As shown in Fig. 2, the brake control device 10 includes a control pump 22, a brake unit 6, a brake operation device 7, an operation amount sensor 5, a mode switching valve 1, an electromagnetic proportional pressure reducing valve 2, an emergency brake switching valve 3, a relief valve 9, and a controller 4.

[0029] The control pump 22 discharges hydraulic oil when driven by a drive source (not shown), such as an engine. The control pump 22 is an example of the hydraulic pump in the present disclosure.

[0030] The brake unit 6 is configured to be able to generate a braking force on the winch drum 11 by receiving the supply of the hydraulic oil discharged from the control pump 22.

[0031] The brake unit 6 is configured to be operable to switch between a clutch-on state in which the power of the winch motor 23 is transmitted to the winch drum 11 and a clutch-off state in which the winch drum 11 is disengaged from the winch motor 23 and free rotation of the winch drum 11 is allowed.

[0032] The brake unit 6 has a piston 6a, a spring 6d, a plurality of plates 6e including an inner plate and an outer plate, and a unit case 6f that houses these. The inside of the unit case 6f is partitioned into a positive clutch chamber 6b, a negative clutch chamber 6c, and a plate chamber in which the plurality of plates 6e are arranged. The piston 6a is displaceable with respect to the unit case 6f in its axial direction. The axial direction is a direction in which the piston 6a approaches the plurality of plates 6e or a direction in which the piston 6a moves away from the plurality of plates 6e.

[0033] When the piston 6a moves in the axial direction, the state of the brake unit 6 switches between the clutch-on state (the state in which the brake is applied) and the clutch-off state (the state in which the brake is released). Specifically, when the piston 6a moves in a direction approaching the plurality of plates 6e, a pressing force is applied to the plurality of plates 6e so that the inner plate and the outer plate in the plurality of plates 6e come into contact. As a result, the state of the brake unit 6 becomes the clutch-on state. On the other hand, when the piston 6a moves in a direction away from the plurality of plates 6e, the inner plate and the outer plate are separated. As a result, the state of the brake unit 6 becomes the clutch-off state. The spring 6d biases the piston 6a in a direction in which the state of the brake unit 6 becomes the clutch-on state, that is, a direction in which the piston 6a approaches the plurality of plates 6e.

[0034] In this embodiment, when the pressure in the positive clutch chamber 6b is the same as the pressure in the negative clutch chamber 6c, the state of the brake unit 6 becomes the clutch-on state due to the biasing force of the spring 6d. On the other hand, when the pressure in the negative clutch chamber 6c becomes greater than the pressure in the positive clutch chamber 6b, and the force generated due to this differential pressure (i.e., the force in the direction of moving the piston 6a away from the plurality of plates 6e) becomes greater than the biasing force of the spring 6d, the state of the brake unit 6 becomes the clutch-off state.

[0035] The brake operation device 7 is provided with a brake operation for adjusting the braking force on the winch drum 11 by the operator. The brake operation device 7 is an example of the operation device in the present disclosure. The brake operation device 7 has a brake pedal 7a (foot pedal) as an operation member.

[0036] When a brake operation (pedal operation) by the operator is applied to the brake pedal 7a of the brake operation device 7, the operation amount sensor 5 detects the operation amount of the pedal operation and inputs a brake detection signal, which is a detection signal corresponding to the detected operation amount, to the controller 4.

[0037] The mode switching valve 1 is interposed between the control pump 22 and the brake unit 6. The mode switching valve 1 switches between a first state (right side position in FIG. 2) in which the control pump 22 and the brake unit 6 are connected via the electromagnetic proportional pressure reducing valve 2, and a second state (left side position in FIG. 2) in which the control pump 22 and the brake unit 6 are connected bypassing the electromagnetic proportional pressure reducing valve 2 (without passing through the electromagnetic proportional pressure reducing valve 2). In this embodiment, when the state of the mode switching valve 1 is the first state, the control pump 22, the electromagnetic proportional pressure reducing valve 2, the mode switching valve 1, and the brake unit 6 are connected in this order. When the state of the mode switching valve 1 is the second state, the control pump 22, the mode switching valve 1, and the brake unit 6 are connected in this order, and the electromagnetic proportional pressure reducing valve 2 is not interposed between the control pump 22 and the mode switching valve 1. The mode switching valve 1 is an example of the switching valve according to the present disclosure.

[0038] The mode switching valve 1 is an electromagnetic switching valve that switches between a first state and a second state according to a mode command signal from the controller 4. Specifically, in the present embodiment, when the solenoid of the mode switching valve 1 is in a non-excited state, the state of the mode switching valve 1 becomes the second state (the left position in FIG. 2), and when the solenoid of the mode switching valve 1 is in an excited state, the state of the mode switching valve 1 becomes the first state (the right position in FIG. 2).

[0039] The electromagnetic proportional pressure reducing valve 2 opens and closes so that the pressure of the hydraulic oil supplied to the brake unit 6 is adjusted according to the operation amount of the brake operation (pedal operation) in the free mode described later. Specifically, in the present embodiment, the controller 4 outputs a brake command signal to the electromagnetic proportional pressure reducing valve 2 according to the operation amount of the brake operation (pedal operation), and the electromagnetic proportional pressure reducing valve 2 opens and closes so that the pressure of the hydraulic oil supplied to the positive clutch chamber 6b of the brake unit 6 is adjusted according to the brake command signal from the controller 4.

[0040] Due to its structure, the electromagnetic proportional pressure reducing valve 2 is not necessarily suitable for operations that supply a large flow rate. One of the reasons is that, for example, the cross-sectional area of the flow path through which the hydraulic oil flows in the electromagnetic proportional pressure reducing valve 2 is smaller than the cross-sectional area of the flow path through which the hydraulic oil flows in the mode switching valve 1 and the cross-sectional area of the flow path through which the hydraulic oil flows in the emergency brake switching valve 3.

[0041] The emergency brake switching valve 3 is configured to be switchable between a supply position (the right position in FIG. 2) that allows the hydraulic oil from the control pump 22 to be supplied to the negative clutch chamber 6c, and a discharge position (the left position in FIG. 2) that allows the hydraulic oil in the negative clutch chamber 6c to be discharged from the negative clutch chamber 6c to the tank 27. In the present embodiment, the emergency brake switching valve 3 is constituted by a solenoid valve (electromagnetic switching valve). In the present embodiment, the solenoid of the emergency brake switching valve 3 is in an excited state as shown in FIG. 2 during normal times, and the spool of the emergency brake switching valve 3 is set to the supply position. When a failure such as a disconnection occurs and the secondary pressure of the electromagnetic proportional pressure reducing valve 2 decreases while the mode switching valve 1 is in the first state (the solenoid is in the excited state), the controller 4 switches the emergency brake switching valve 3 to a non-excited state. As a result, the spool of the emergency brake switching valve 3 switches from the supply position to the discharge position, and the negative clutch chamber 6c is connected to the tank 27. Thereby, a braking force is generated on the winch drum 11, that is, a state in which a brake is applied to the winch drum 11 is achieved. The brake control device 10 may further include a schematic pressure sensor that detects the secondary pressure of the electromagnetic proportional pressure reducing valve 2, and the controller 4 may determine whether a failure such as a disconnection has occurred based on the pressure detection signal input from the pressure sensor and the brake detection signal.

[0042] When the mode switching valve 1 is in the second state (the solenoid is in the non-excited state), pressures corresponding to the secondary pressure of the control pump 22 are supplied to both the positive clutch chamber 6b and the negative clutch chamber 6c. Therefore, due to the biasing force of the spring 6d, the state of the brake unit 6 becomes the clutch-on state. Hereinafter, the mode of the brake control device 10 when the mode switching valve 1 is in the second state (the solenoid is in the non-excited state) may be referred to as the brake mode.

[0043] In this braking mode, a braking force is constantly generated on the winch drum 11, that is, the winch drum 11 is in a braked state (clutch-on state). In this clutch-on state, the power of the winch motor 23 is transmitted to the winch drum 11. Therefore, in response to the winch operation by the operator applied to the winch operation lever 25a, the winch drum 11 rotates by the power of the winch motor 23, and the rope R is wound or unwound.

[0044] When the state of the mode switching valve 1 is the first state (the solenoid is in the excited state), the secondary pressure of the electromagnetic proportional pressure reducing valve 2 is applied to the positive clutch chamber 6b. Hereinafter, the mode of the brake control device 10 when the state of the mode switching valve 1 is the first state (the solenoid is in the excited state) may be referred to as the free mode.

[0045] In this free mode, according to the output from the electromagnetic proportional pressure reducing valve 2, the balance between the pressure in the positive clutch chamber 6b and the pressure in the negative clutch chamber 6c changes, and the piston 6a is displaced in its axial direction relative to the unit case 6f. When a brake detection signal corresponding to the operation amount of the brake operation is input from the operation amount sensor 5 to the controller 4, the controller 4 outputs a brake command signal corresponding to the brake detection signal to the electromagnetic proportional pressure reducing valve 2, and the electromagnetic proportional pressure reducing valve 2 outputs a secondary pressure corresponding to the brake command signal input from the controller 4. That is, the electromagnetic proportional pressure reducing valve 2 outputs a secondary pressure corresponding to the operation amount of the brake operation. Specifically, the electromagnetic proportional pressure reducing valve 2 outputs a larger secondary pressure as the operation amount of the brake operation increases. When the output (secondary pressure) of the electromagnetic proportional pressure reducing valve 2 increases, the braking force on the winch drum 11 also increases, and the winch drum 11 is in a braked state. When the output (secondary pressure) of the electromagnetic proportional pressure reducing valve 2 decreases, the braking force on the winch drum 11 also decreases, and the brake on the winch drum 11 is released. Therefore, in the free mode, the operator can switch between the state of applying a brake to the winch drum 11 and the state of releasing the brake by adjusting the operation amount of the brake operation. In the state where the brake is released in the free mode, the suspended load 106 can freely fall by its own weight. The speed of this free fall can be increased or decreased according to the operation amount of the brake pedal 7a.

[0046] The crane 100 may further include a mode switching switch 30. The mode switching switch 30 is a switch for switching the mode of the brake control device 10 between the brake mode and the free mode. The mode switching switch 30 is configured to be operable by an operator, for example, by being provided inside the cab of the crane.

[0047] When the mode switch 30 receives a free mode operation by the operator, it inputs a free mode signal to the controller 4, and the controller 4 controls the operation of the mode switching valve 1 so that the state of the mode switching valve 1 becomes the first state (the right position in FIG. 2). Thereby, the mode of the brake control device 10 is switched to the free mode. On the other hand, when the mode switch 30 receives a brake mode operation by the operator, it inputs a brake mode signal to the controller 4, and the controller 4 controls the operation of the mode switching valve 1 so that the state of the mode switching valve 1 becomes the second state (the left position in FIG. 2). Thereby, the mode of the brake control device 10 is switched to the brake mode.

[0048] When the pressure in the discharge line (the discharge line from which the hydraulic oil is discharged from the control pump 22) connected to the control pump 22 exceeds a predetermined value, the relief valve 9 opens to allow at least a part of the hydraulic oil to flow to the tank 27.

[0049] In order to prevent seizure of the plurality of plates 6e due to friction generated between the inner plate and the outer plate, as shown in FIG. 2, the brake unit 6 is configured such that cooling oil is supplied to the plate chamber.

[0050] The controller 4 includes a computer including an arithmetic processing device such as an MPU and a memory. The controller 4 controls the operation of the mode switching valve 1 so that the mode switching valve 1 switches from the first state to the second state when a determination condition preset for determining that a sudden braking operation has been applied to the brake operation device 7 is satisfied.

[0051] In this embodiment, the determination condition is a condition (first determination condition) that the operation amount of the braking operation exceeds an operation amount threshold value which is a preset value. The operation amount in an emergency braking operation usually becomes the maximum operation amount that can be applied to the brake pedal 7a of the braking operation device 7 or a large operation amount close to this. Therefore, in this embodiment, the controller 4 can determine whether an emergency braking operation has been applied to the brake pedal 7a by comparing the operation amount of the braking operation with the operation amount threshold value.

[0052] FIG. 3 is a graph showing an example of the relationship between the operation amount of the braking operation and the clutch pressure in the brake control device 10 according to this embodiment. In FIG. 3, the horizontal axis is the ratio (unit: %) of the operation amount (pedal operation amount) of the braking operation applied to the brake pedal 7a when the maximum operation amount is 100, and the vertical axis is the clutch pressure (unit: MPa). The clutch pressure is the pressure supplied to the positive clutch chamber 6b of the brake unit 6. In FIG. 3, the clutch pressure is shown by a solid line. The horizontal straight line shown by a broken line in FIG. 3 indicates the level of the clutch pressure at which a braking force sufficient to stop the rotation of the winch drum 11 can be generated. The vertical straight line shown by a one-dot chain line in FIG. 3 indicates the operation amount threshold value.

[0053] As shown in FIG. 3, when the pedal operation amount is equal to or less than the operation amount threshold value, the clutch pressure is a value corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2, gradually increases according to the pedal operation amount, and becomes a constant value (the maximum value of the secondary pressure of the electromagnetic proportional pressure reducing valve 2) when the pedal operation amount is equal to or more than a certain value. Due to its structure, the electromagnetic proportional pressure reducing valve 2 is good at controlling static pressure, but is not necessarily suitable for operations such as rapidly increasing the pressure or supplying a large flow rate.

[0054] When the pedal operation amount exceeds the operation amount threshold value, that is, when the determination condition is satisfied, the controller 4 controls the operation of the mode switching valve 1 so that the mode switching valve 1 switches from the first state to the second state. As a result, the control pump 22 and the positive clutch chamber 6b of the brake unit 6 are connected without passing through the electromagnetic proportional pressure reducing valve 2, and the clutch pressure switches to a value corresponding to the secondary pressure of the control pump 22. As shown in FIG. 3, the secondary pressure of the control pump 22 is a pressure capable of generating a braking force sufficient to stop the rotation of the winch drum 11. In the present embodiment, the secondary pressure of the control pump 22 is a pressure higher than the maximum value of the secondary pressure of the electromagnetic proportional pressure reducing valve 2. As shown in FIG. 3, when the mode switching valve 1 switches from the first state to the second state, the clutch pressure rapidly increases from the secondary pressure of the electromagnetic proportional pressure reducing valve 2 to the secondary pressure of the control pump 22.

[0055] When the pedal operation amount is equal to or less than the operation amount threshold value, the secondary pressure of the electromagnetic proportional pressure reducing valve increases proportionally as the pedal operation amount increases, and a clutch pressure (a clutch pressure capable of stopping the suspended load from descending) sufficient to stop the rotation of the winch drum 11 before the pedal operation amount reaches the operation amount threshold value can be generated.

[0056] When the pedal operation amount increases gently, as shown in FIG. 3, the clutch pressure switches from the state where it has reached the maximum value of the secondary pressure of the electromagnetic proportional pressure reducing valve 2 to the secondary pressure of the control pump 22. In this case, there is not much sudden increase in the clutch pressure.

[0057] On the other hand, when the operator performs an emergency braking operation such as quickly and deeply depressing the brake pedal 7a, the pedal operation amount exceeds the operation amount threshold almost simultaneously with the start of the pedal operation, and the mode switching valve 1 switches from the first state to the second state. As a result, when an emergency braking operation is applied to the brake pedal 7a of the braking operation device 7, the secondary pressure of the control pump 22 is quickly transmitted to the brake unit 6. Therefore, when an emergency braking operation is performed, hydraulic oil with a large flow rate can be quickly supplied to the positive clutch chamber 6b of the brake unit 6 without being affected by the electromagnetic proportional pressure reducing valve 2 in terms of time. As a result, it is possible to suppress an increase in the brake response time when an emergency braking operation is performed.

[0058] Next, with reference to FIG. 4, the operation of the brake control device 10 according to the present embodiment will be described. FIG. 4 is a flowchart showing an example of arithmetic processing by the controller 4.

[0059] When the mode of the brake control device 10 is set to the brake mode, that is, when the state of the mode switching valve 1 is the second state, the controller 4 determines whether an operation by the operator has been applied to the mode switching switch 30 (step S1). When a free mode signal is input from the mode switching switch 30 (YES in step S1), the controller 4 controls the operation of the mode switching valve 1 so that the state of the mode switching valve 1 switches from the second state to the first state (that is, the solenoid of the mode switching valve 1 is in an excited state), and switches the mode of the brake control device 10 to the free mode (step S2).

[0060] Next, based on the detection signal input from the operation amount sensor 5, the controller 4 determines whether the operation amount of the brake operation applied to the brake pedal 7a of the brake operation device 7 exceeds the operation amount threshold value (step S3). When the operation amount of the brake operation is equal to or less than the operation amount threshold value (NO in step S3), the state of the mode switching valve 1 is maintained in the first state (step S5). When the free mode is switched to the brake mode while the processes of step S3 and step S5 are repeatedly performed, the controller 4 ends the process shown in FIG. 4.

[0061] On the other hand, when the operation amount of the brake operation exceeds the operation amount threshold value (YES in step S3), the controller 4 controls the operation of the mode switching valve 1 so that the mode switching valve 1 switches from the first state to the second state (that is, so that the solenoid of the mode switching valve 1 is de-energized) (step S4).

[0062] FIG. 5 is a graph showing an example of the relationship between the operation speed of the brake operation and the clutch pressure in the brake control device 10 according to Modification 1 of the present embodiment. In the brake control device 10 according to this Modification 1, the determination condition is different from the determination condition of the brake control device 10 shown in FIG. 3. Other configurations of the brake control device 10 according to Modification 1 are the same as those of the brake control device 10 shown in FIG. 2. Hereinafter, Modification 1 will be described with reference to FIGS. 2 and 5.

[0063] In Modification 1, the determination condition is the condition (second determination condition) that the operation speed of the braking operation exceeds a preset operation speed threshold value. The operation speed in an emergency braking operation (i.e., the pedal operation speed when depressing the brake pedal 7a in an emergency braking operation) usually tends to be a large operation speed. Therefore, in this Modification 1, the controller 4 can determine whether an emergency braking operation has been applied to the brake pedal 7a of the braking operation device 7 by comparing the operation speed of the braking operation with the operation speed threshold value. Specifically, for example, even if the operator intends to perform a braking operation that exceeds the operation amount threshold value, there may be a case where the brake pedal 7a has not been depressed sufficiently in reality. In this case, if the determination condition is the first determination condition (the condition using the operation amount threshold value), the state of the mode switching valve 1 is maintained in the first state. On the other hand, in this Modification 1, since the determination condition is the second determination condition (the condition using the operation speed threshold value), even if the operation amount does not exceed the operation amount threshold value, if the pedal operation speed exceeds the operation speed threshold value, the state of the mode switching valve 1 switches from the first state to the second state. Therefore, the second determination condition in Modification 1 is a condition that is more responsive to the braking operation (fast pedal operation) that the operator often performs in a scenario where the operator wants to apply the brake instantaneously. Thus, in Modification 1, it is possible to more appropriately determine whether an emergency braking operation has been applied.

[0064] In this Modification 1, the controller 4 controls the operation of the mode switching valve 1 so that the mode switching valve 1 switches from the first state to the second state when the second determination condition is satisfied.

[0065] In FIG. 5, the horizontal axis represents the operation speed (pedal operation speed) of the braking operation, and the vertical axis represents the clutch pressure (unit: MPa). The clutch pressure is the pressure supplied to the positive clutch chamber 6b of the brake unit 6. The broken line shown by the dashed line in FIG. 5 indicates the state (first state or second state) of the mode switching valve 1. The vertical straight line shown by the dash-dotted line in FIG. 5 indicates the operation speed threshold value.

[0066] As shown in FIG. 5, when the pedal operation speed is equal to or lower than the operation speed threshold value, the clutch pressure becomes a value corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2, that is, a value corresponding to the pedal operation amount.

[0067] On the other hand, when the pedal operation speed exceeds the operation speed threshold value, that is, when the second determination condition is satisfied, the controller 4 controls the operation of the mode switching valve 1 so that the mode switching valve 1 switches from the first state to the second state. Thereby, the control pump 22 and the positive clutch chamber 6b of the brake unit 6 are connected without passing through the electromagnetic proportional pressure reducing valve 2, and the clutch pressure switches to a value corresponding to the secondary pressure of the control pump 22. As shown in FIG. 5, when the state of the mode switching valve 1 switches from the first state to the second state, the clutch pressure rapidly increases from the secondary pressure of the electromagnetic proportional pressure reducing valve 2 to the secondary pressure of the control pump 22 (pump pressure in FIG. 5).

[0068] FIG. 6 is a diagram showing a hydraulic circuit and a controller 4 of a brake control device 10 according to Modification 2 of the present embodiment. The brake control device 10 according to this Modification 2 is different from the brake control device 10 shown in FIG. 2 in that it further includes a switching valve 12 (a switching valve dedicated for emergency braking) and a check valve 8. Other configurations of the brake control device 10 according to Modification 2 are the same as those of the brake control device 10 shown in FIG. 2. The switching valve 12 dedicated for emergency braking is an example of the switching valve (second switching valve) in the present disclosure and is interposed between the control pump 22 and the brake unit 6.

[0069] In the brake control device 10 shown in Fig. 2, the mode switching valve 1 serves to switch between the free mode and the brake mode, and to quickly supply the secondary pressure of the control pump 22 to the positive clutch chamber 6b of the brake control device 10 when a sudden braking operation is applied to the brake pedal 7a. On the other hand, in this Modification 2, the above two functions are shared by the mode switching valve 1 and the dedicated switching valve 12 for sudden braking. That is, the mode switching valve 1 is responsible for switching between the free mode and the brake mode, and the dedicated switching valve 12 for sudden braking is responsible for quickly supplying the secondary pressure of the control pump 22 to the positive clutch chamber 6b of the brake control device 10 when a sudden braking operation is applied to the brake pedal 7a.

[0070] The dedicated switching valve 12 for sudden braking is an electromagnetic switching valve with a higher responsiveness to the command signal from the controller 4 than the mode switching valve 1. For the function of switching between the free mode and the brake mode, the size of the spool and the size of the coil of the mode switching valve 1 are larger than the size of the spool and the size of the coil of the dedicated switching valve 12 for sudden braking. The dedicated switching valve 12 for sudden braking has a structure specialized for the response during sudden braking, and its responsiveness to the command signal from the controller 4 is further enhanced compared to the mode switching valve 1. By arranging these switching valves 1 and 12 in parallel in the hydraulic circuit, the switching operation between the free mode and the brake mode by the mode switching valve 1 and the quick response during sudden braking become smoother compared to the brake control device shown in Fig. 2.

[0071] The switching valve 12 is arranged in parallel with the mode switching valve 1 between the control pump 22 and the positive clutch chamber 6b of the brake unit 6. A check valve 8 is arranged in the line connecting the switching valve 12 and the positive clutch chamber 6b. The check valve 8 allows the flow of hydraulic oil from the switching valve 12 toward the positive clutch chamber 6b, while blocking the flow of hydraulic oil from the positive clutch chamber 6b toward the switching valve 12. When the solenoid of the switching valve 12 is de-energized (the left position in Fig. 6, the first state), the switching valve 12 is connected to the tank 27. When the solenoid of the switching valve 12 is energized (the right position in Fig. 6, the second state), the switching valve 12 switches so that the control pump 22 and the positive clutch chamber 6b of the brake unit 6 are connected without passing through the electro-hydraulic proportional pressure reducing valve 2. The check valve 8 prevents the pressure in the positive clutch chamber 6b from becoming the pressure of the tank 27 by preventing the positive clutch chamber 6b from communicating with the tank 27 when the switching valve 12 is in the de-energized state.

[0072] When the determination condition is satisfied, the controller 4 switches the switching valve 12 so that the control pump 22 and the positive clutch chamber 6b of the brake unit 6 are connected without passing through the electro-hydraulic proportional pressure reducing valve 2. Thereby, when a sudden braking operation is applied to the brake pedal 7a of the brake operating device 7, the secondary pressure of the control pump 22 is transmitted to the brake unit 6 more quickly than in the brake control device 10 shown in Fig. 2. As a result, it is further suppressed that the brake response time becomes long when a sudden braking operation is performed. In the second modification, the determination condition may be either the first determination condition or the second determination condition.

[0073] [Modification Example] The present disclosure is not limited to the embodiments described above. The present disclosure includes, for example, the following forms.

[0074] (A) Regarding the determination condition In the above embodiment, the determination condition is that the operation amount of the braking operation exceeds the operation amount threshold value (the first determination condition). In Modification Example 1 of the above embodiment, the determination condition is that the operation speed of the braking operation exceeds the operation speed threshold value (the second determination condition). However, the determination condition according to the present disclosure includes both the first determination condition and the second determination condition. The controller may be configured to switch the switching valve so that when the first determination condition is satisfied and the second determination condition is satisfied, the brake unit bypasses the electromagnetic proportional pressure reducing valve and is connected to the hydraulic pump. Specifically, when the first determination condition is satisfied and the second determination condition is satisfied, the controller may control the operation of the mode switching valve 1 so that the mode switching valve 1 switches from the first state to the second state in the hydraulic circuit of FIG. 2, and in the hydraulic circuit of FIG. 6, the dedicated switching valve 12 for emergency braking may control the operation of the dedicated switching valve 12 for emergency braking so that it switches from the first state to the second state. When the determination condition includes both the first determination condition and the second determination condition in this way, it is possible to more appropriately determine whether an emergency braking operation has been applied compared to the case where the determination condition is the second determination condition. Specifically, for example, when the suspended load 106 is freely falling due to its own weight, the operator may perform a braking operation to reduce the falling speed of the suspended load 106 instead of an emergency braking operation to stop the falling operation of the suspended load 106. In such a case, for example, even if the operation amount of the braking operation does not exceed the operation amount threshold value (even if the first determination condition is not satisfied), when the operation speed of the braking operation exceeds the operation speed threshold value (when the second determination condition is satisfied), the state of the switching valve switches from the first state to the second state. In this case, an emergency brake is applied to stop the falling operation of the suspended load 106, and this emergency brake may not match the operator's feeling. On the other hand, when the determination condition includes both the first determination condition and the second determination condition, the state of the switching valve switches from the first state to the second state only when both the first determination condition and the second determination condition are satisfied. Thereby, the determination of whether an emergency braking operation has been applied becomes closer to the operator's feeling.

[0075] (B) Regarding the switching valve In the above-described specific example, each of the mode switching valve 1 and the dedicated switching valve 12 for emergency braking is configured such that when the solenoid is in a non-excited state, the state of the switching valve becomes the second state, and when the solenoid is in an excited state, the state of the switching valve becomes the first state. However, at least one of the mode switching valve 1 and the dedicated switching valve 12 for emergency braking may be configured such that when the solenoid is in a non-excited state, the state of the switching valve becomes the first state, and when the solenoid is in an excited state, the state of the switching valve becomes the second state.

Explanation of Signs

[0076] 1: Mode switching valve 2: Electro-hydraulic proportional pressure reducing valve 3: Emergency braking switching valve 4: Controller 5: Operation amount sensor 6: Brake unit 7: Brake operating device 7a: Brake pedal 8: Check valve 10: Brake control device 11: Winch drum 12: Electromagnetic switching valve 22: Control pump 100: Crane 101: Lower traveling body 103: Upper slewing body 104: Boom R: Rope

Claims

1. A brake control device, comprising: a hydraulic pump; a brake unit capable of generating a braking force on a winch drum by receiving the supply of hydraulic oil discharged from the hydraulic pump; an operating device to which a brake operation for adjusting the braking force is applied; an electromagnetic proportional pressure reducing valve that opens and closes so that the pressure of the hydraulic oil supplied to the brake unit is adjusted according to the operation amount of the brake operation; a mode switching valve interposed between the hydraulic pump and the brake unit, the mode switching valve for switching the mode of the brake control device between a free mode in which the braking force can be adjusted according to the operation amount of the brake operation and a brake mode in which the winch drum can be rotated by the power of a winch motor; a controller that switches the mode of the brake control device from the free mode to the brake mode and connects the brake unit to the hydraulic pump bypassing the electromagnetic proportional pressure reducing valve when a preset determination condition for determining that an emergency brake operation has been applied to the operating device is satisfied. A brake control device comprising:

2. A brake control device, comprising: a hydraulic pump; a brake unit capable of generating a braking force on a winch drum by receiving the supply of hydraulic oil discharged from the hydraulic pump; an operating device to which a brake operation for adjusting the braking force is applied; an electromagnetic proportional pressure reducing valve that opens and closes so that the pressure of the hydraulic oil supplied to the brake unit is adjusted according to the operation amount of the brake operation; a switching valve interposed between the hydraulic pump and the brake unit; a controller that switches the switching valve so that the brake unit is connected to the hydraulic pump bypassing the electromagnetic proportional pressure reducing valve when a preset determination condition for determining that an emergency brake operation has been applied to the operating device is satisfied; a mode switching valve for switching the mode of the brake control device between a free mode and a brake mode; and the switching valve is a second switching valve arranged in parallel with the mode switching valve between the hydraulic pump and the brake unit, the second switching valve is an electromagnetic switching valve having a higher responsiveness to a command signal from the controller than the mode switching valve. A brake control device

3. The brake control device according to claim 1 or 2, wherein the determination condition includes a condition that the operation amount of the brake operation exceeds an operation amount threshold that is a preset threshold.

4. 4. The brake control device according to claim 1, wherein the determination condition includes a condition that an operation speed of the brake operation exceeds an operation speed threshold that is a preset threshold.

5. The aircraft and a raising and lowering member attached to the fuselage so as to be able to raise and lower; The winch drum is for winding and unwinding the rope hanging from the hoisting member; A crane comprising: the brake control device according to any one of claims 1 to 4, which is capable of adjusting the braking force applied to the winch drum.

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