JP7707909B2 - Brake control device and crane equipped with same - Google Patents

Description

This disclosure relates to a brake control device and a crane equipped with the same.

Generally, a crane comprises a self-propelled lower running body, an upper rotating body supported for rotation on the lower running body, a hoisting member including a boom attached to the upper rotating body so that it can be raised and lowered, a hook suspended from the tip of the hoisting member via a rope, and a winch for winding in and letting out the rope.

Patent Document 1 discloses a winch control device that controls the operation of a winch. This winch control device includes a winch, a state change valve (state change unit), a pressure control valve, and a braking force adjustment unit. The pressure control valve is a valve that converts a command from the braking force adjustment unit into hydraulic pressure. The pressure control valve is a valve that controls (adjusts) the braking force when the winch is in a free state (when the change position of the state change valve is 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 reducer, and a clutch.

The clutch switches the state of connection (degree of connection) between the motor and 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 chamber, and a separation chamber. The opening of the pressure control valve changes in response to a command from the braking force adjustment unit, and the pressure in the pressure chamber changes. The braking force of the winch (clutch) changes in response to the pressure in the pressure chamber.

JP 2019-055880 A

When the pressure control valve is an electromagnetic proportional pressure reducing valve, the structure of the electromagnetic proportional pressure reducing valve makes it good at controlling static pressure, but it may not necessarily be suitable for operations that supply a large flow rate. Also, in order to ensure sufficient brake capacity in the clutch (brake unit), the pressure-receiving area of the pressure contact chamber (positive chamber) and the separation chamber (negative chamber), the stroke of the piston, and the piston volume (product of the pressure-receiving area and the stroke) are large. Therefore, when an operator applies sudden braking, the flow rate of hydraulic oil required in the brake unit (the value obtained by dividing the piston volume by the brake response time) becomes large. However, with flow rate control by a pressure control valve constituted by an electromagnetic proportional pressure reducing valve, the flow rate of hydraulic oil required in the brake unit when sudden braking is applied may not be supplied to the brake unit quickly. In this case, the brake response time may become long.

The present disclosure aims to provide a brake control device that can prevent the brake response time from becoming longer when a sudden braking operation is performed, and a crane equipped with the same.

The brake control device provided includes a tank for storing hydraulic oil, a hydraulic pump for discharging the hydraulic oil, a brake unit having a positive chamber that receives the pressure of the hydraulic oil to generate a force in a direction to increase the braking force on the winch drum, and a negative chamber that receives the pressure of the hydraulic oil to generate a force in a direction to decrease the braking force, an operating device that applies a brake operation to adjust the braking force, an electromagnetic proportional pressure reducing valve that opens and closes so that the pressure of the hydraulic oil supplied to the positive chamber is adjusted according to the amount of operation of the brake operation, a first switching valve that switches between a pump connection state in which the negative chamber is connected to the hydraulic pump and a tank connection state in which the negative chamber is connected to a tank, and a controller that controls the operation of the first switching valve so that the pump connection state is switched to the tank connection state when a preset judgment condition is satisfied to judge that a sudden braking operation has been applied to the operating device.

In this brake control device, when the judgment condition is satisfied, the controller controls the operation of the first switching valve so that the pump connection state is switched to the tank connection state, and the pressure in the negative chamber of the brake unit quickly drops from the pressure corresponding to the secondary pressure of the hydraulic pump to the pressure corresponding to the tank pressure. Therefore, in this brake control device, braking force can be generated more quickly than when the electromagnetic proportional pressure reducing valve operates in response to sudden braking to generate braking force. This prevents the brake response time from becoming longer when sudden braking is performed.

The judgment condition preferably includes that the operation amount of the brake operation exceeds a preset operation amount threshold. The operation amount in a sudden braking operation is usually the maximum operation amount that can be applied to the operation device or a large operation amount close to this. Therefore, in this configuration, the controller can judge whether a sudden braking operation has been applied to the operation device by comparing the operation amount of the brake operation with the operation amount threshold.

The judgment condition preferably includes that the operation speed of the brake operation exceeds a preset operation speed threshold. The operation speed in a sudden brake operation is usually a large operation speed. Therefore, in this configuration, the controller can judge whether a sudden brake operation has been applied to the operating device by comparing the operation speed of the brake operation with the operation speed threshold.

The brake control device further includes a second switching valve that switches between a first state in which the positive chamber is connected to the hydraulic pump via the electromagnetic proportional pressure reducing valve and a second state in which the positive chamber is connected to the hydraulic pump by bypassing the electromagnetic proportional pressure reducing valve, and the controller is preferably configured to control the operation of the second switching valve so that the first state is switched to the second state when the judgment condition is met. When the judgment condition is met, the pump connection state is switched to the tank connection state, and the pressure in the negative chamber is quickly reduced to a pressure corresponding to the pressure of the tank, and hydraulic oil flows into the positive chamber. In order to ensure the flow rate of hydraulic oil to this positive chamber, the controller controls the operation of the second switching valve so that the positive chamber is connected to the hydraulic pump without passing through the electromagnetic proportional pressure reducing valve when the judgment condition is met. Therefore, it is easier to ensure the flow rate of hydraulic oil to the positive chamber compared to when hydraulic oil flows into the positive chamber via an electromagnetic proportional pressure reducing valve that is not suitable for operations that supply a large flow rate. This can reduce the possibility of cavitation occurring when hydraulic oil flows into the positive chamber.

The brake control device may further include a second switching valve that switches between a first state in which the positive chamber is connected to the hydraulic pump via the electromagnetic proportional pressure reducing valve and a second state in which the positive chamber is connected to the tank by bypassing the electromagnetic proportional pressure reducing valve, and the controller may be configured to control the operation of the second switching valve so that the first state is switched to the second state when the judgment condition is met. When the judgment condition is met, the pump connection state is switched to the tank connection state, and the pressure in the negative chamber is quickly reduced to a pressure corresponding to the pressure of the tank, and hydraulic oil flows into the positive chamber. In order to ensure the flow rate of hydraulic oil to this positive chamber, the controller controls the operation of the second switching valve so that the positive chamber is connected to the tank without passing through the electromagnetic proportional pressure reducing valve when the judgment condition is met. Therefore, it is easier to ensure the flow rate of hydraulic oil to the positive chamber compared to when hydraulic oil flows into the positive chamber via an electromagnetic proportional pressure reducing valve that is not suitable for operations that supply a large flow rate. This can reduce the possibility of cavitation occurring when hydraulic oil flows into the positive chamber.

The crane provided includes a machine body, a hoisting member attached to the machine body so that it can be raised or lowered, the winch drum for winding and unwinding the rope hanging down from the hoisting member, and the above-mentioned brake control device capable of adjusting the braking force applied to the winch drum. With this crane, it is possible to prevent the brake response time from becoming long when a sudden braking operation is performed.

The present disclosure provides a brake control device that can prevent the brake response time from becoming longer when a sudden braking operation is performed, and a crane equipped with the same.

FIG. 1 is a side view showing a crane equipped with a brake control device according to an embodiment of the present disclosure. FIG. 2 is a diagram showing a hydraulic circuit and a controller of the brake control device according to the embodiment. 4 is a graph showing an example of a relationship between an operation amount and a pressure of a brake operation in the brake control device according to the embodiment. 5 is a flowchart showing an example of a calculation process performed by the controller. 5 is a graph showing an example of a relationship between an operation speed and a pressure of a brake operation in the brake control device according to the first modified example of the embodiment. FIG. 11 is a diagram showing a hydraulic circuit and a controller of a brake control device according to a second modified example of the embodiment.

The following describes in detail the embodiments of the present disclosure with reference to the drawings.

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 running body 101, an upper rotating body 103 supported on the lower running body 101 so as to be rotatable about an axis, a hoisting member attached to the upper rotating body 103 so as to be able to be raised and lowered, a hook 105 suspended from the tip of the hoisting member via a rope R, a gantry 107 attached to the upper rotating body 103, and a winch drum 11. The lower running body 101 and the upper rotating body 103 are examples of a machine body. In the crane 100 shown in FIG. 1, the hoisting member is composed of a boom 104, but the hoisting member may further include a jib (not shown) attached to the tip of the boom 104. The crane 100 may also include a mast instead of the gantry 107.

The winch drum 11 winds or unwinds the rope R connected to the hook 105, causing the hook 105 to perform a lifting and lowering operation for lifting work. The rope R is unwound from the winch drum 11, passes through the tip of the hoisting member, and is arranged so as to hang down from the tip of the hoisting member to suspend the hook 105. A load 106 is suspended from the hook 105. The winch drum 11 is arranged so that its rotation axis coincides with the width direction of the upper rotating body 103. In this embodiment, the winch drum 11 is supported by the upper rotating body 103, but it may also be supported by the boom 104.

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 reducer 28.

The main pump 21 discharges hydraulic oil by being driven by a driving source (not shown), such as an engine.

The winch motor 23 is a hydraulic motor for rotating the winch drum 11. In this embodiment, the winch motor 23 has an output shaft 23a that rotates upon receiving hydraulic oil from the main pump 21. The winch motor 23 has a first port and a second port, and when hydraulic oil is supplied to one of these ports, the output shaft 23a rotates in the direction corresponding to the one port and operates to discharge hydraulic oil from the other port.

The winch control valve 24 is interposed between the main pump 21 and the winch motor 23, and selectively directs hydraulic oil for driving the winch motor 23 from the main pump 21 to one of the first and second ports of the winch motor 23 to control the direction of the hydraulic oil supplied to the winch motor 23 and to control 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.

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 of the winch operation given by the operator to the winch operation lever 25a. 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 connected to the first pilot port and the second pilot port of the winch control valve 24, respectively, 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 given to the winch operation lever 25a, out of the first and second pilot ports. The pilot pump may be the control pump 22 described later, or may be a pump separate from the control pump 22.

The winch control valve 24 is held in the neutral position (center position in FIG. 2) when pilot pressure is not input to either the first or second pilot port. In this neutral position, the main pump 21 and the winch motor 23 are disconnected 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.

When a certain pilot pressure or more is supplied to the first pilot port, the winch control valve 24 shifts from the neutral position to the first drive position (upper position in Figure 2) with a stroke corresponding to the magnitude of the pilot pressure. In this first drive position, 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 hydraulic oil is discharged from the second port. This causes the output shaft 23a of the winch motor 23 to rotate in the first direction. The discharged hydraulic oil returns to the tank 27.

When a certain pilot pressure or more is supplied to the second pilot port, the winch control valve 24 shifts from the neutral position to the second drive position (lower position in Figure 2) with a stroke corresponding to the magnitude of the pilot pressure. In this second drive position, 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 hydraulic oil is discharged from the first port. This causes the output shaft 23a of the winch motor 23 to rotate in the second direction. The discharged hydraulic oil returns to the tank 27.

The reducer 28 is disposed 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 reducer 28 is formed, for example, of a planetary gear mechanism. A plate 6e in the brake unit 6, which will be described later, is connected to the carrier shaft of the reducer 28.

The crane 100 includes a brake control device 10. As shown in FIG. 2, the brake control device 10 includes the tank 27, the control pump 22, the brake unit 6, the brake operating device 7, the operation amount sensor 5, the mode change valve 1, the electromagnetic proportional pressure reducing valve 2, the emergency brake change valve 3, the relief valve 9, and the controller 4. The emergency brake change valve 3 is an example of a first change valve in the present disclosure, and the mode change valve 1 is an example of a second change valve in the present disclosure. The tank 27 stores hydraulic oil.

The control pump 22 discharges hydraulic oil by being driven by a drive source (not shown), such as an engine. The control pump 22 is an example of a hydraulic pump in this disclosure.

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

The brake unit 6 is configured to be switchable 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 disconnected from the winch motor 23 and allows the winch drum 11 to rotate freely.

The brake unit 6 has a piston 6a, a spring 6d, a number of plates 6e including an inner plate and an outer plate, and a unit case 6f that houses them. The unit case 6f is divided into a positive clutch chamber 6b, a negative clutch chamber 6c, and a plate chamber in which the multiple plates 6e are arranged. The piston 6a can be displaced in its axial direction relative to the unit case 6f. The axial direction is the direction in which the piston 6a approaches the multiple plates 6e or the direction in which the piston 6a moves away from the multiple plates 6e.

The positive clutch chamber 6b receives hydraulic oil pressure from the control pump 22 and generates a force in a direction that increases the braking force on the winch drum 11, i.e., a force in a direction that moves the piston 6a closer to the multiple plates 6e. The positive clutch chamber 6b is an example of a positive chamber in this disclosure. The negative clutch chamber 6c receives hydraulic oil pressure from the control pump 22 and generates a force in a direction that decreases the braking force on the winch drum 11, i.e., a force in a direction that moves the piston 6a away from the multiple plates 6e. The negative clutch chamber 6c is an example of a negative chamber in this disclosure.

When the piston 6a moves in the axial direction, the state of the brake unit 6 switches between the clutch-on state (a state in which the brakes are applied) and the clutch-off state (a state in which the brakes are released). Specifically, when the piston 6a moves in a direction approaching the plates 6e, it applies a pressing force to the plates 6e so that the inner plates and outer plates of the plates 6e come into contact with each other. 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 plates 6e, the inner plates and the outer plates are separated from each other. 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, in a direction in which the piston 6a approaches the plates 6e.

In this embodiment, when the pressure in the positive clutch chamber 6b and the pressure in the negative clutch chamber 6c are the same, the brake unit 6 is in 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 the pressure difference between them (i.e., the force in the direction moving the piston 6a away from the multiple plates 6e) becomes greater than the biasing force of the spring 6d, the brake unit 6 is in the clutch-off state.

The brake operating device 7 is used by the operator to apply a brake operation to adjust the braking force applied to the winch drum 11. The brake operating device 7 is an example of an operating device in this disclosure. The brake operating device 7 has a brake pedal 7a (foot pedal) as an operating member.

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

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 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 position in FIG. 2) in which the control pump 22 and the brake unit 6 are connected by bypassing the electromagnetic proportional pressure reducing valve 2 (without passing through the electromagnetic proportional pressure reducing valve 2). Specifically, the first state is a state in which the positive clutch chamber 6b of the brake unit 6 is connected to the control pump 22 via the electromagnetic proportional pressure reducing valve 2. The second state is a state in which the positive clutch chamber 6b of the brake unit 6 is connected to the control pump 22 by bypassing 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 positive clutch chamber 6b of the brake unit 6 are connected in this order. When the mode change valve 1 is in the second state, the control pump 22, the mode change valve 1, and the positive clutch chamber 6b of 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 change valve 1.

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

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

The electromagnetic proportional pressure reducing valve 2 is not necessarily suitable for operations that supply large flow rates due to its structure. One of the reasons for this is that, for example, the cross-sectional area of the flow passage through which hydraulic oil flows in the electromagnetic proportional pressure reducing valve 2 is smaller than the cross-sectional area of the flow passage through which hydraulic oil flows in the mode switching valve 1 and the cross-sectional area of the flow passage through which hydraulic oil flows in the emergency brake switching valve 3.

The emergency brake changeover valve 3 is configured to be switchable between a supply position (left position in FIG. 2) that allows hydraulic oil from the control pump 22 to be supplied to the negative clutch chamber 6c, and a discharge position (right position in FIG. 2) that allows hydraulic oil in the negative clutch chamber 6c to be discharged from the negative clutch chamber 6c to the tank 27. In other words, the emergency brake changeover valve 3 switches between a pump connection state in which the negative clutch chamber 6c is connected to the control pump 22, and a tank connection state in which the negative clutch chamber 6c is connected to the tank 27. In the pump connection state, hydraulic oil pressure from the control pump 22 is supplied to the negative clutch chamber 6c. In this embodiment, the emergency brake changeover valve 3 is configured by an electromagnetic valve (electromagnetic changeover valve).

In this embodiment, the solenoid of the emergency brake switching valve 3 is normally in a non-energized state as shown in FIG. 2, the spool of the emergency brake switching valve 3 is set to the supply position, and the state of the emergency brake switching valve 3 is set to the pump connection state. When the mode switching valve 1 is in the first state (the solenoid is excited), if a failure such as a wire break occurs and the secondary pressure of the electromagnetic proportional pressure reducing valve 2 drops, the controller 4 switches the solenoid of the emergency brake switching valve 3 to the excited state. As a result, the spool of the emergency brake switching valve 3 switches from the supply position to the discharge position. That is, the state of the emergency brake switching valve 3 switches from the pump connection state to the tank connection state, and the negative clutch chamber 6c is connected to the tank 27. As a result, a braking force is generated on the winch drum 11, that is, the brake is applied to the winch drum 11.

The brake control device 10 may further include a pressure sensor (not shown) that detects the secondary pressure of the electromagnetic proportional pressure reducing valve 2. The controller 4 may determine whether or not a fault such as a broken wire has occurred based on the pressure detection signal input from the pressure sensor and the brake detection signal.

When the mode change valve 1 is in the second state (solenoid is de-energized), pressure corresponding to the secondary pressure of the control pump 22 is supplied to both the positive clutch chamber 6b and the negative clutch chamber 6c, and the brake unit 6 is in the clutch-on state due to the biasing force of the spring 6d. Hereinafter, the mode of the brake control device 10 when the mode change valve 1 is in the second state (solenoid is de-energized) may be referred to as the brake mode.

In this brake mode, a braking force is constantly applied to the winch drum 11, i.e., the winch drum 11 is braked (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.

When the mode change valve 1 is in the first state (the solenoid is energized), 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 mode change valve 1 is in the first state (the solenoid is energized) may be referred to as the free mode.

In this free mode, the balance between the pressure in the positive clutch chamber 6b and the pressure in the negative clutch chamber 6c changes according to the output from the electromagnetic proportional pressure reducing valve 2, and the piston 6a is displaced in its axial direction relative to the unit case 6f. When a brake detection signal corresponding to the amount of operation 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 amount of operation of the brake operation. Specifically, the electromagnetic proportional pressure reducing valve 2 outputs a larger secondary pressure as the amount of operation 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 brake on the winch drum 11 is applied. 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 free mode, the operator can switch between a braked state and a released state for the winch drum 11 by adjusting the amount of brake operation. When the brake is released in free mode, the load 106 can fall freely under its own weight. The speed of this free fall can be increased or decreased depending on the amount of operation of the brake pedal 7a.

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

When the mode change 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 change valve 1 so that the state of the mode change valve 1 becomes the first state (the right position in FIG. 2). This switches the mode of the brake control device 10 to the free mode. On the other hand, when the mode change 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 change valve 1 so that the state of the mode change valve 1 becomes the second state (the left position in FIG. 2). This switches the mode of the brake control device 10 to the brake mode.

The relief valve 9 opens to allow at least a portion of the hydraulic oil to flow to the tank 27 when the pressure in the discharge line connected to the control pump 22 (the discharge line through which the hydraulic oil is discharged from the control pump 22) exceeds a predetermined value.

To prevent the multiple plates 6e from seizing due to friction between the inner plate and the outer plate, as shown in Figure 2, the brake unit 6 is configured so that cooling oil is supplied to the plate chamber.

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 emergency brake switching valve 3 so that the pump connection state is switched to the tank connection state when a preset determination condition is satisfied to determine that an emergency braking operation has been applied to the brake operating device 7.

In this embodiment, the judgment condition is that the amount of braking operation exceeds a preset operation amount threshold (first judgment condition). The amount of operation in a sudden braking operation is usually the maximum amount of operation that can be applied to the brake pedal 7a of the brake operation device 7 or a large amount of operation close to this maximum amount. Therefore, in this embodiment, the controller 4 can judge whether a sudden braking operation has been applied to the brake pedal 7a by comparing the amount of braking operation with the operation amount threshold.

Figure 3 is a graph showing an example of the relationship between the amount of brake operation (pedal operation amount) and pressure (clutch pressure) in the brake control device 10 according to this embodiment. In Figure 3, the horizontal axis is the ratio (unit: %) of the amount of brake operation (pedal operation amount) given to the brake pedal 7a when the maximum operation amount is 100, and the vertical axis is pressure (unit: MPa). In Figure 3, the solid line indicates the pressure (positive clutch pressure) supplied to the positive clutch chamber 6b of the brake unit 6. The dashed line indicates the pressure (negative clutch pressure) supplied to the negative clutch chamber 6c of the brake unit 6. The dashed line indicates the differential pressure (negative clutch pressure - positive clutch pressure) obtained by subtracting the pressure supplied to the positive clutch chamber 6b from the pressure supplied to the negative clutch chamber 6c. In Figure 3, the vertical line indicated by the dashed double-dashed line indicates the operation amount threshold.

In the free mode, which adjusts the braking force on the winch drum 11 according to the brake operation applied to the brake pedal 7a of the brake operation device 7, the state of the mode switching valve 1 is set to the first state, and the state of the emergency brake switching valve 3 is set to the pump connection state.

In this free mode, in the specific example shown in FIG. 3, the positive clutch pressure behaves as follows. The minimum value of the positive clutch pressure is the positive clutch pressure when the pedal operation amount is zero, and is a pressure corresponding to the pressure of the tank 27. The maximum value of the positive clutch pressure is a pressure corresponding to the secondary pressure of the control pump 22. As shown in FIG. 3, as the pedal operation amount increases from zero, the opening area of the electromagnetic proportional pressure reducing valve 2 also increases. Therefore, as shown in FIG. 3, as the pedal operation amount increases, the positive clutch pressure also increases. When the pedal operation amount increases to a certain value (pump pressure corresponding value), the positive clutch pressure reaches a pressure corresponding to the secondary pressure of the control pump 22. Therefore, even if the pedal operation amount becomes larger than the pump pressure corresponding value, the positive clutch pressure remains constant at the pressure corresponding to the secondary pressure of the control pump 22. In the specific example of FIG. 3, the pump pressure corresponding value is a value smaller than the operation amount threshold, and even if the pedal operation amount becomes larger than the operation amount threshold, the positive clutch pressure remains constant at the pressure corresponding to the secondary pressure of the control pump 22.

On the other hand, the negative clutch pressure behaves as follows. In the region (pump connection region) where the pedal operation amount is from zero to the operation amount threshold, the spool of the emergency brake switching valve 3 is held in the supply position, and the state of the emergency brake switching valve 3 is maintained in the pump connection state, so that the negative clutch pressure is held at a pressure corresponding to the secondary pressure of the control pump 22. Therefore, in this pump connection region, the differential pressure between the negative clutch pressure and the positive clutch pressure (negative clutch pressure - positive clutch pressure) gradually decreases as the pedal operation amount increases from zero, and becomes almost 0 MPa when the pedal operation amount becomes the pump pressure corresponding value. The differential pressure is held at a constant value (almost 0 MPa) in the region where the pedal operation amount is between the pump pressure corresponding value and the operation amount threshold. In the region where this differential pressure is a constant value (almost 0 MPa), a braking force sufficient to stop the rotation of the winch drum 11 (a braking force that can stop the suspended load from descending) can be generated by the biasing force of the spring 6d. Therefore, it is possible to generate a braking force sufficient to stop the rotation of the winch drum 11 before the pedal operation amount reaches the operation amount threshold.

In this embodiment, when the pedal operation amount exceeds the operation amount threshold, the controller 4 controls the operation of the emergency brake switching valve 3 so that the pump connection state is switched to the tank connection state. As a result, the negative clutch chamber 6c is connected to the tank 27, and as shown in FIG. 3, the negative clutch pressure instantly drops from the pressure corresponding to the secondary pressure of the control pump 22 to the pressure corresponding to the pressure of the tank 27 (pressure near 0 MPa). At this time, the positive clutch pressure is maintained at the pressure corresponding to the secondary pressure of the control pump 22, so the differential pressure (negative clutch pressure - positive clutch pressure) becomes a negative value. When the differential pressure becomes a negative value, a larger braking force is generated compared to the region where the differential pressure is a constant value (almost 0 MPa). In the region where the pedal operation amount is larger than the operation amount threshold, the negative clutch chamber 6c is maintained in a state where it is connected to the tank 27, so the differential pressure is maintained at a negative value.

When the pedal operation amount increases slowly, the pressure difference drops to a negative value from a certain value (almost 0 MPa) at which sufficient braking force is generated, as shown in Figure 3. In this case, it is assumed that the winch drum 11 has already stopped when the pressure difference drops to a negative value.

On the other hand, when the operator performs an emergency braking operation by quickly and deeply depressing the brake pedal 7a, the pedal operation amount exceeds the operation amount threshold almost at the same time as the pedal operation starts, and the state of the emergency brake switching valve 3 switches from the pump connection state to the tank connection state. In other words, when an emergency braking operation is applied to the brake pedal 7a of the brake operation device 7, the negative clutch pressure instantly drops from the pressure corresponding to the secondary pressure of the control pump 22 to the pressure corresponding to the pressure of the tank 27. Therefore, when an emergency braking operation is performed, sufficient braking force can be generated quickly without being affected by the time due to the electromagnetic proportional pressure reducing valve 2. This prevents the brake response time from becoming longer when an emergency braking operation is performed.

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

When the mode of the brake control device 10 is set to the brake mode, i.e., when the state of the mode switching valve 1 is the second state, the controller 4 determines whether or not an operation has been given to the mode switching switch 30 by the operator (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 mode switching valve 1 switches from the second state to the first state (i.e., so that 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).

Next, the controller 4 determines whether the amount of brake operation applied to the brake pedal 7a of the brake operation device 7 exceeds the operation amount threshold based on the detection signal input from the operation amount sensor 5 (step S3). If the amount of brake operation is equal to or less than the operation amount threshold (NO in step S3), the state of the emergency brake switching valve 3 is maintained in the pump connection state (step S5). Note that when the processes of steps S3 and S5 are being repeated, if the free mode is switched to the brake mode, the controller 4 ends the process shown in FIG. 4.

On the other hand, when the amount of operation of the brake operation exceeds the operation amount threshold (YES in step S3), the controller 4 controls the operation of the emergency brake switching valve 3 so that the state of the emergency brake switching valve 3 switches from the pump connection state to the tank connection state (i.e., so that the solenoid of the emergency brake switching valve 3 becomes excited) (step S4). As a result, the negative clutch chamber 6c is connected to the tank 27, and the negative clutch pressure instantly drops from the pressure (pump pressure) corresponding to the secondary pressure of the control pump 22 to the pressure (tank pressure) corresponding to the pressure of the tank 27. At this time, since the positive clutch chamber 6b is maintained in a state connected to the control pump 22, the positive clutch pressure is held at the pressure (pump pressure) corresponding to the secondary pressure of the control pump 22. Therefore, the differential pressure (negative clutch pressure - positive clutch pressure) becomes a negative value, and a large brake pressure is generated quickly. This prevents the brake response time from becoming long when a sudden brake operation is performed.

Moreover, when the judgment condition is satisfied, the controller 4 according to this embodiment preferably controls the operation of the emergency brake switching valve 3 so that the pump connection state is switched to the tank connection state, and also controls the operation of the mode switching valve 1 so that the first state is switched to the second state in order to suppress the occurrence of cavitation. Specifically, this is as follows.

When the above-mentioned judgment condition is met, the pump connection state is switched to the tank connection state, and the pressure in the negative clutch chamber 6c instantly drops to the tank pressure, so that at least a portion of the hydraulic oil in the negative clutch chamber 6c is discharged outside the negative clutch chamber 6c and hydraulic oil flows into the positive clutch chamber 6b. In order to ensure the flow rate of hydraulic oil to the positive clutch chamber 6b, the controller 4 controls the operation of the mode switching valve 1 so that the first state (right position in FIG. 2) is switched to the second state (left position in FIG. 2) when the above-mentioned judgment condition is met. As a result, the positive clutch chamber 6b is connected to the control pump 22 by bypassing the electromagnetic proportional pressure reducing valve 2 (without passing through the electromagnetic proportional pressure reducing valve 2). This makes it easier to ensure the flow rate of hydraulic oil to the positive clutch chamber 6b compared to when hydraulic oil flows into the positive clutch chamber 6b through the electromagnetic proportional pressure reducing valve 2, which is not suitable for operations that supply a large flow rate. This reduces the possibility of cavitation occurring when hydraulic oil flows into the positive clutch chamber 6b.

Figure 5 is a graph showing an example of the relationship between the operating speed and pressure of the brake operation in the brake control device 10 according to Modification 1 of this embodiment. In the brake control device 10 according to Modification 1, the judgment conditions are different from the judgment conditions of the brake control device 10 shown in Figure 3. The other configurations of the brake control device 10 according to Modification 1 are similar to those of the brake control device 10 shown in Figure 2. Below, Modification 1 will be described with reference to Figures 2 and 5.

In the first modification, the judgment condition is that the operation speed of the brake operation exceeds a preset operation speed threshold (second judgment condition). The operation speed in a sudden braking operation (i.e., the pedal operation speed at which the brake pedal 7a is depressed in a sudden braking operation) is usually high. Therefore, in the first modification, the controller 4 can judge whether a sudden braking operation has been applied to the brake pedal 7a of the brake operation device 7 by comparing the operation speed of the brake operation with the operation speed threshold.

In this variant 1, the controller 4 controls the operation of the emergency brake switching valve 3 so that the state of the emergency brake switching valve 3 switches from the pump connection state to the tank connection state when the second judgment condition is satisfied.

In FIG. 5, the horizontal axis indicates the operating speed of the brake operation (pedal operating speed), and the vertical axis indicates the pressure (unit: MPa). In FIG. 5, the solid line indicates the pressure (positive clutch pressure) supplied to the positive clutch chamber 6b of the brake unit 6. The dashed line indicates the pressure (negative clutch pressure) supplied to the negative clutch chamber 6c. The dashed line indicates the state of the emergency brake changeover valve 3, the notation "emergency brake valve OFF" indicates that the state of the emergency brake changeover valve 3 is in the pump connected state, and the notation "emergency brake valve ON" indicates that the state of the emergency brake changeover valve 3 is in the tank connected state. The vertical straight line indicated by the dashed double-dot line indicates the operation speed threshold.

In the modified example 1 shown in FIG. 5, as in the embodiment shown in FIG. 3, in the free mode, the state of the mode switching valve 1 is set to the first state, and the state of the emergency brake switching valve 3 is set to the pump connection state.

As shown in FIG. 5, in the free mode, the positive clutch pressure is a value corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2, i.e., a value according to the pedal operation amount, regardless of the pedal operation speed.

On the other hand, the negative clutch pressure behaves as follows: In the free mode, in the region where the pedal operation speed is from zero to the operation speed threshold (pump connection region), the spool of the emergency brake changeover valve 3 is held in the supply position and the state of the emergency brake changeover valve 3 is maintained in the pump connection state, so the negative clutch pressure is held at a pressure (pump pressure) corresponding to the secondary pressure of the control pump 22.

In this modified example 1, when the pedal operation speed exceeds the operation speed threshold, i.e., when the second judgment condition is satisfied, the controller 4 controls the operation of the emergency brake changeover valve 3 so that the state of the emergency brake changeover valve 3 switches from the pump connection state to the tank connection state. As a result, the negative clutch chamber 6c is connected to the tank 27, and as shown in FIG. 5, the negative clutch pressure instantly drops from the pump pressure to a pressure (tank pressure) corresponding to the pressure of the tank 27. At this time, the positive clutch pressure is a pressure corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2 (pressure corresponding to the amount of pedal operation). Therefore, the differential pressure between the negative clutch pressure and the positive clutch pressure (negative clutch pressure - positive clutch pressure) becomes a negative value, and a large braking force is generated.

When the judgment condition is the first judgment condition (condition using the operation amount threshold), even if the operator thinks that he or she has performed a brake operation that exceeds the operation amount threshold, if the brake pedal 7a is not actually depressed sufficiently, the state of the emergency brake changeover valve 3 is maintained in the pump connection state. On the other hand, in the above-mentioned modified example 1, even if the operation amount does not exceed the operation amount threshold, if the pedal operation speed exceeds the operation speed threshold, the state of the emergency brake changeover valve 3 is switched from the pump connection state to the tank connection state. Therefore, the second judgment condition in modified example 1 is a condition that is more suited to the brake operation (fast pedal operation) that the operator often performs when he or she wants to apply the brakes instantly. Therefore, modified example 1 can more appropriately judge whether or not a sudden brake operation has been performed.

Figure 6 is a diagram showing the hydraulic circuit and controller 4 of the brake control device 10 according to Modification 2 of this embodiment. The brake control device 10 according to Modification 2 differs from the brake control device 10 shown in Figure 2 in that it is configured so that both the positive clutch chamber 6b and the negative clutch chamber 6c are connected to the tank 27 when the judgment condition is satisfied. The 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 Figure 2.

As shown in FIG. 6, the mode switching valve 1 switches between a first state (right side position in FIG. 6) in which the positive clutch chamber 6b is connected to the control pump 22 or the tank 27 via the electromagnetic proportional pressure reducing valve 2, and a second state (left side position in FIG. 6) in which the positive clutch chamber 6b bypasses the electromagnetic proportional pressure reducing valve 2 and is connected to the control pump 22 or the tank 27.

When the mode switching valve 1 is in the first state (right position in FIG. 6) and the emergency brake switching valve 3 is in the pump connected state (left position in FIG. 6), the positive clutch chamber 6b is connected to at least one of the control pump 22 and the tank 27 via the electromagnetic proportional pressure reducing valve 2. When the mode switching valve 1 is in the first state (right position in FIG. 6) and the emergency brake switching valve 3 is in the tank connected state (right position in FIG. 6), the positive clutch chamber 6b is connected to at least one of the control pump 22 and the tank 27 via the electromagnetic proportional pressure reducing valve 2.

When the mode change valve 1 is in the second state (left position in FIG. 6) and the emergency brake change valve 3 is in the pump connected state (left position in FIG. 6), the positive clutch chamber 6b is connected to the control pump 22, bypassing the electromagnetic proportional pressure reducing valve 2 (without going through the electromagnetic proportional pressure reducing valve 2). When the mode change valve 1 is in the second state (left position in FIG. 6) and the emergency brake change valve 3 is in the tank connected state (right position in FIG. 6), the positive clutch chamber 6b is connected to the tank 27, bypassing the electromagnetic proportional pressure reducing valve 2 (without going through the electromagnetic proportional pressure reducing valve 2).

In the second modification shown in FIG. 6, as in the embodiment shown in FIG. 3, in the free mode, the mode switching valve 1 is set to the first state (right position in FIG. 6), and the emergency brake switching valve 3 is set to the pump connected state (left position in FIG. 6). Therefore, in the free mode, the pressure supplied to the positive clutch chamber 6b (positive clutch pressure) becomes a value corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2, that is, a value according to the pedal operation amount.

In the free mode, when the judgment condition (first judgment condition or second judgment condition) is not satisfied, that is, in the region where the pedal operation amount is from zero to the operation amount threshold (pump connection region) or the region where the pedal operation speed is from zero to the operation speed threshold (pump connection region), the spool of the emergency brake changeover valve 3 is held in the supply position, and the state of the emergency brake changeover valve 3 is maintained in the pump connection state. Therefore, the pressure supplied to the negative clutch chamber 6c (negative clutch pressure) is held at a pressure (pump pressure) corresponding to the secondary pressure of the control pump 22.

When the judgment condition is satisfied, the controller 4 controls the operation of the emergency brake switching valve 3 so that the state of the emergency brake switching valve 3 is switched from the pump connection state (left position in FIG. 6) to the tank connection state (right position in FIG. 6), and controls the operation of the mode switching valve 1 so that the state of the mode switching valve 1 is switched from the first state (right position in FIG. 6) to the second state (left position in FIG. 6). As a result, both the positive clutch chamber 6b and the negative clutch chamber 6c are connected to the tank 27. As a result, the pressure in the positive clutch chamber 6b instantly drops from a value corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2 (i.e., a value corresponding to the pedal operation amount) to a pressure corresponding to the pressure of the tank 27 (tank pressure), and the pressure in the negative clutch chamber 6c instantly drops from the pump pressure to a pressure corresponding to the pressure of the tank 27 (tank pressure). As a result, the piston 6a moves in a direction approaching the multiple plates 6e due to the biasing force of the spring 6d, and a braking force sufficient to stop the rotation of the winch drum 11 can be quickly generated. This prevents the brake response time from becoming longer when sudden braking is performed.

As the piston 6a moves in a direction approaching the multiple plates 6e, at least a portion of the hydraulic oil in the negative clutch chamber 6c is discharged out of the negative clutch chamber 6c, and hydraulic oil flows into the positive clutch chamber 6b. In this modified example 2, when the above-mentioned judgment condition is met, not only is the negative clutch chamber 6c connected to the tank 27, but the positive clutch chamber 6b is connected to the tank 27 without passing through the electromagnetic proportional pressure reducing valve 2. This makes it easier to ensure the flow rate of hydraulic oil into the positive clutch chamber 6b compared to when hydraulic oil flows into the positive clutch chamber 6b through the electromagnetic proportional pressure reducing valve 2. This reduces the possibility of cavitation occurring when hydraulic oil flows into the positive clutch chamber 6b.

[Modification]
The present disclosure is not limited to the above-described embodiment. The present disclosure includes, for example, the following aspects.

(A) Regarding the judgment condition In the above embodiment, the judgment condition is that the operation amount of the brake operation exceeds the operation amount threshold (first judgment condition), and in the first modified example of the above embodiment, the judgment condition is that the operation speed of the brake operation exceeds the operation speed threshold (second judgment condition). However, the judgment condition according to the present disclosure may include both the first judgment condition and the second judgment condition, and the controller may control the operation of the emergency brake switching valve (first switching valve) so that the pump connection state is switched to the tank connection state when the first judgment condition is satisfied and the second judgment condition is satisfied. In this way, when the judgment condition includes both the first judgment condition and the second judgment condition, it is possible to more appropriately determine whether or not an emergency brake operation has been applied compared to when the judgment condition is the second judgment condition. Specifically, for example, when the suspended load 106 is falling freely due to its own weight, the operator may perform a brake operation to reduce the falling speed of the suspended load 106 rather than a sudden brake operation to stop the falling motion of the suspended load 106. In such a case, for example, even if the amount of braking operation does not exceed the operation amount threshold (even if the first judgment condition is not satisfied), when the operating speed of the braking operation exceeds the operating speed threshold (when the second judgment condition is satisfied), the state of the emergency brake changeover valve 3 is switched from the pump connected state to the tank connected state. In this case, sudden braking is applied to stop the falling motion of the suspended load 106, and this sudden braking may not match the operator's sense. On the other hand, when the judgment conditions include both the first judgment condition and the second judgment condition, the state of the emergency brake changeover valve 3 is switched from the pump connected state to the tank connected state only when both the first judgment condition and the second judgment condition are satisfied. This makes it possible to determine whether or not a sudden braking operation has been applied closer to the operator's sense.

(B) Regarding the switching valve In the specific example described above, the emergency brake switching valve 3 is configured so that the state of the switching valve 3 is the pump connected state when the solenoid is in a de-energized state, and the state of the switching valve 3 is the tank connected state when the solenoid is in an excited state. However, the emergency brake switching valve 3 may also be configured so that the state of the switching valve 3 is the tank connected state when the solenoid is in a de-energized state, and the state of the switching valve 3 is the pump connected state when the solenoid is in an excited state.

The mode switching valve 1 is configured so that the state of the switching valve is the second state when the solenoid is in a de-energized state and the state of the switching valve is the first state when the solenoid is in an energized state. However, the mode switching valve 1 may be configured so that the state of the switching valve is the first state when the solenoid is in a de-energized state and the state of the switching valve is the second state when the solenoid is in an energized state.

1: Mode switching valve (an example of a second switching valve)
2: Electromagnetic proportional pressure reducing valve 3: Emergency brake changeover valve (an example of a first changeover valve)
4: Controller 5: Operation amount sensor 6: Brake unit 6b: Positive clutch chamber 6c: Negative clutch chamber 7: Brake operation device (an example of an operation device)
10: Brake control device 11: Winch drum 22: Control pump (an example of a hydraulic pump)
27: Tank 100: Crane 101: Undercarriage (an example of the aircraft body)
103: Upper rotating body (an example of the aircraft)
104: Boom (an example of a lifting member)
R: Rope

Claims (5)

A tank for storing hydraulic oil;
A hydraulic pump that discharges the hydraulic oil;
A brake unit having a positive chamber that receives the pressure of the hydraulic oil to generate a force in a direction that increases the braking force on the winch drum, and a negative chamber that receives the pressure of the hydraulic oil to generate a force in a direction that decreases the braking force;
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 as to adjust the pressure of the hydraulic oil supplied to the positive chamber in accordance with the amount of the brake operation;
a first switching valve that switches between a pump connection state in which the negative chamber is connected to the hydraulic pump and a tank connection state in which the negative chamber is connected to a tank;
a controller that controls an operation of the first switching valve so that the pump connection state is switched to the tank connection state when a preset determination condition is satisfied in order to determine that a sudden braking operation has been applied to the operating device;
a second switching valve that switches between a first state in which the positive chamber is connected to the hydraulic pump via the electromagnetic proportional pressure reducing valve and a second state in which the positive chamber is connected to the hydraulic pump by bypassing the electromagnetic proportional pressure reducing valve ,
The controller controls an operation of the second switching valve so that the first state is switched to the second state when the determination condition is satisfied . A tank for storing hydraulic oil;
A hydraulic pump that discharges the hydraulic oil;
A brake unit having a positive chamber that receives the pressure of the hydraulic oil to generate a force in a direction that increases the braking force on the winch drum, and a negative chamber that receives the pressure of the hydraulic oil to generate a force in a direction that decreases the braking force;
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 as to adjust the pressure of the hydraulic oil supplied to the positive chamber in accordance with the amount of the brake operation;
a first switching valve that switches between a pump connection state in which the negative chamber is connected to the hydraulic pump and a tank connection state in which the negative chamber is connected to a tank;
a controller that controls an operation of the first switching valve so that the pump connection state is switched to the tank connection state when a preset determination condition is satisfied in order to determine that a sudden braking operation has been applied to the operating device;
a second switching valve that switches between a first state in which the positive chamber is connected to the hydraulic pump via the electromagnetic proportional pressure reducing valve and a second state in which the positive chamber is connected to the tank, bypassing the electromagnetic proportional pressure reducing valve;
The controller controls an operation of the second switching valve so that the first state is switched to the second state when the determination condition is satisfied. 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 a preset operation amount threshold. 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. The aircraft and
A lifting member attached to the airframe in a liftable manner;
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.