JP7715038B2 - 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 rotatably supported on the lower running body, a boom-raising member that is attached to the upper rotating body so that it can be raised and lowered, a hook suspended from the tip of the boom-raising member via a rope, and a winch that winds in and unwinds 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 converts commands from the braking force adjustment unit into hydraulic pressure. The pressure control valve controls (adjusts) the braking force when the winch is in a free state (when the state change 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 reducer, and a clutch.

The clutch switches the state of connection (degree of connection) between the motor and winch drum. The clutch brakes the rotation of the winch drum. The clutch comprises a housing, clutch plates, a clutch cylinder, and a spring. The clutch cylinder comprises a piston that can press the clutch plates, a pressure chamber, and a separation chamber. The opening of the pressure control valve changes in response to commands from the braking force adjustment unit, changing the pressure in the pressure chamber. The braking force of the winch (clutch) changes depending on the pressure in the pressure chamber.

JP 2019-055880 A

However, when the pressure control valve is an electromagnetic proportional pressure reducing valve, due to its structure, while it is good at controlling static pressure, it may not necessarily be suited to operations that require the supply of large flow rates. Furthermore, to ensure sufficient brake capacity in the clutch (brake unit), the pressure-receiving area of the pressure contact chamber and the separation chamber, the piston stroke, and the piston volume (the product of the pressure-receiving area and the stroke) must be large. Therefore, when the operator applies the brakes suddenly, the flow rate of hydraulic oil required by the brake unit (piston capacity divided by the brake response time) increases. However, with flow control using a pressure control valve composed of an electromagnetic proportional pressure reducing valve, the flow rate of hydraulic oil required by the brake unit when the brakes are applied suddenly may not be supplied to the brake unit quickly enough. This can result in a long brake response time.

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

The brake control device provided includes a hydraulic pump, a brake unit capable of generating a braking force on a winch drum by receiving a supply of hydraulic oil discharged from the hydraulic pump, an operating device to which a brake operation is applied to adjust the braking force, an electromagnetic proportional pressure reducing valve that opens and closes to adjust the pressure of the hydraulic oil supplied to the brake unit depending on the amount of braking operation, a switching valve interposed between the hydraulic pump and the brake unit, and 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 predetermined determination conditions are met to determine that an emergency braking operation has been applied to the operating device.

In this brake control device, when the determination condition is met, the controller controls the operation of the switching valve so that the brake unit is connected to the hydraulic pump bypassing the electromagnetic proportional pressure reducing valve (i.e., so that the hydraulic pump and brake unit are connected without going through the electromagnetic proportional pressure reducing valve). This allows the secondary pressure of the hydraulic pump to be quickly transmitted to the brake unit when a sudden braking operation is performed on the operating device. Therefore, in this brake control device, a large flow rate of hydraulic oil can be quickly supplied to the brake unit when a sudden braking operation is performed, without being affected by the time delay caused by the electromagnetic proportional pressure reducing valve. This prevents the brake response time from becoming longer when a sudden braking operation is performed.

Preferably, the determination condition includes the operation amount of the brake operation exceeding 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 operating device, or a large operation amount close to this maximum operation amount. Therefore, in this configuration, the controller can determine whether a sudden braking operation has been applied to the operating device by comparing the operation amount of the brake operation with the operation amount threshold.

Preferably, the determination condition includes whether the operating speed of the brake operation exceeds a preset operating speed threshold. The operating speed during a sudden braking operation is usually high. Therefore, in this configuration, the controller can determine whether a sudden braking operation has been applied to the operating device by comparing the operating speed of the brake operation with the operating speed threshold.

The brake control device may further include a mode change valve for switching the mode of the brake control device between free mode and brake mode, the change valve being a second change valve arranged in parallel with the mode change valve between the hydraulic pump and the brake unit, and the second change valve being an electromagnetic change valve that is more responsive to command signals from the controller than the mode change valve. In this configuration, by arranging two change valves (the mode change valve and the second change valve) in parallel in the hydraulic circuit, the switching operation between free mode and brake mode by the mode change valve and the rapid response to sudden braking are performed more smoothly.

The crane provided comprises a machine body, a hoisting member attached to the machine body so that it can be raised or lowered, a winch drum for winding in and letting out the rope hanging from the hoisting member, and the above-mentioned brake control device that can adjust the braking force applied to the winch drum. This crane can prevent the brake response time from becoming long when sudden braking is performed.

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

1 is a side view showing a crane equipped with a brake control device according to an embodiment of the present disclosure. FIG. 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 amount of brake operation and a clutch pressure in the brake control device according to the embodiment. 4 is a flowchart illustrating an example of a calculation process performed by the controller. 10 is a graph showing an example of a relationship between a brake operation speed and a clutch pressure in the brake control device according to the first modified example of the embodiment. FIG. 10 is a diagram illustrating a hydraulic circuit and a controller of a brake control device according to a second modification of the embodiment.

Embodiments of the present disclosure will be described in detail below 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 comprises a self-propelled lower carrier 101, an upper rotating body 103 supported on the lower carrier 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 carrier 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 be equipped with 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 lifting and lowering operations for load lifting operations. The rope R is unwound from the winch drum 11, passes through the tip of the hoisting member, and is arranged to hang down from the tip of the hoisting member, suspending 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 is driven by a drive source (not shown), such as an engine, to discharge hydraulic oil.

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

The winch control valve 24 is located 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, controlling the direction of hydraulic oil supplied to the winch motor 23 and the flow rate of 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 operating device 25 has a winch operating lever 25a and a pilot valve 25b (remote control valve). The winch operating lever 25a rotates in the direction of a winch operation applied by the operator to the winch operating 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 and second pilot ports of the winch control valve 24, respectively, via pilot lines. The pilot valve 25b opens to allow pilot pressure corresponding to the magnitude of the winch operation to be supplied from the pilot pump to one of the first and second pilot ports corresponding to the direction of the winch operation applied to the winch operating lever 25a. The pilot pump may be the control pump 22, described below, or a pump separate from the control pump 22.

The winch control valve 24 is held in the neutral position (center position in Figure 2) when no pilot pressure is input to either the first or second pilot port. In this neutral position, the main pump 21 and winch motor 23 are disconnected and the center bypass line is opened, allowing hydraulic oil from the main pump 21 to return directly to the tank 27 via the center bypass line.

When a certain level of pilot pressure 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 level of pilot pressure 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 located 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 configured, for example, by a planetary gear mechanism. The carrier shaft of the reducer 28 is connected to the plate 6e of the brake unit 6, which will be described later.

The crane 100 is equipped 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 operating 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.

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 receive hydraulic oil discharged from the control pump 22 and generate braking force on the winch drum 11.

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, allowing the winch drum 11 to rotate freely.

The brake unit 6 includes a piston 6a, a spring 6d, multiple plates 6e including an inner plate and an outer plate, and a unit case 6f that houses these. 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 axially 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.

As 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, as the piston 6a moves toward the multiple plates 6e, it applies a pressing force to the multiple plates 6e so that the inner plates and outer plates of the multiple plates 6e come into contact. As a result, the brake unit 6 enters the clutch-on state. On the other hand, as the piston 6a moves away from the multiple plates 6e, the inner plates and outer plates separate. As a result, the brake unit 6 enters the clutch-off state. The spring 6d biases the piston 6a in a direction that puts the brake unit 6 in the clutch-on state, i.e., in a direction in which the piston 6a approaches the multiple 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 biasing force of the spring 6d causes the brake unit 6 to enter the clutch-on state. 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 by the pressure difference between these chambers (i.e., the force moving the piston 6a away from the multiple plates 6e) becomes greater than the biasing force of the spring 6d, the brake unit 6 enters the clutch-off state.

The brake operating device 7 is used by the operator to apply a brake operation to adjust the braking force on 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 the 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 pedal operation 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 bypassing the electromagnetic proportional pressure reducing valve 2 (without passing through the electromagnetic proportional pressure reducing valve 2). In this embodiment, when the mode switching valve 1 is in 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 mode switching valve 1 is in 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 a switching valve according to the present disclosure.

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 de-energized state, the mode switching valve 1 is in the second state (left position in Figure 2), and when the solenoid of the mode switching valve 1 is in an energized state, the mode switching valve 1 is in the first state (right position in Figure 2).

In free mode, which will be described later, the electromagnetic proportional pressure reducing valve 2 opens and closes to adjust the pressure of hydraulic oil supplied to the brake unit 6 in accordance with 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 in accordance with the amount of brake operation (pedal operation), and the electromagnetic proportional pressure reducing valve 2 opens and closes in accordance with the brake command signal from the controller 4 to adjust the pressure of hydraulic oil supplied to the positive clutch chamber 6b of the brake unit 6.

Due to its structure, the electromagnetic proportional pressure reducing valve 2 is not necessarily suited to operations that supply large flow rates. One reason for this is that the cross-sectional area of the flow path through which hydraulic oil flows in the electromagnetic proportional pressure reducing valve 2 is smaller than the cross-sectional area of the flow path through which hydraulic oil flows in the mode changeover valve 1 and the cross-sectional area of the flow path through which hydraulic oil flows in the emergency brake changeover valve 3.

The emergency brake changeover valve 3 is configured to be switchable between a supply position (right 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 (left 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 this embodiment, the emergency brake changeover valve 3 is configured as a solenoid valve (electromagnetic changeover valve). In this embodiment, the solenoid of the emergency brake changeover valve 3 is normally in an energized state as shown in FIG. 2 , and the spool of the emergency brake changeover valve 3 is set to the supply position. When the mode changeover valve 1 is in the first state (solenoid energized), 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 emergency brake changeover valve 3 to a de-energized state. As a result, the spool of the emergency brake changeover valve 3 switches from the supply position to the discharge position, and the negative clutch chamber 6c is connected to the tank 27. This generates a braking force on the winch drum 11, i.e., the winch drum 11 is braked. 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, and the controller 4 may determine whether 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 (the 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 biasing force of the spring 6d causes the brake unit 6 to enter the clutch-on state. Hereinafter, the mode of the brake control device 10 when the mode change valve 1 is in the second state (the 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 due to 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 in response to the output from the electromagnetic proportional pressure reducing valve 2, causing the piston 6a to displace axially relative to the unit case 6f. When a brake detection signal corresponding to the amount of braking 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. In other words, the electromagnetic proportional pressure reducing valve 2 outputs a secondary pressure corresponding to the amount of braking. Specifically, the electromagnetic proportional pressure reducing valve 2 outputs a greater secondary pressure as the amount of braking is increased. As the output (secondary pressure) of the electromagnetic proportional pressure reducing valve 2 increases, the braking force on the winch drum 11 also increases, resulting in the brake being applied to the winch drum 11. As the output (secondary pressure) of the electromagnetic proportional pressure reducing valve 2 decreases, the braking force on the winch drum 11 also decreases, resulting in the brake on the winch drum 11 being released. Therefore, in free mode, the operator can switch between a braked and 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 is allowed to 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 selector switch 30. The mode selector switch 30 is a switch for switching the mode of the brake control device 10 between brake mode and free mode. The mode selector switch 30 is configured to be operable by an operator, for example, by being provided in the cab of the crane.

When the mode selector switch 30 receives a free mode operation from the operator, it inputs a free mode signal to the controller 4, and the controller 4 controls the operation of the mode selector valve 1 so that the state of the mode selector valve 1 is in the first state (the right position in Figure 2). This switches the mode of the brake control device 10 to free mode. On the other hand, when the mode selector switch 30 receives a brake mode operation from the operator, it inputs a brake mode signal to the controller 4, and the controller 4 controls the operation of the mode selector valve 1 so that the state of the mode selector valve 1 is in the second state (the left position in Figure 2). This switches the mode of the brake control device 10 to brake mode.

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

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 to supply cooling oil to the plate chamber.

The controller 4 includes a computer including an arithmetic processing unit such as an MPU and 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 preset determination conditions are met to determine that a sudden braking operation has been applied to the brake operating device 7.

In this embodiment, the determination condition is that the amount of braking operation exceeds a preset operation amount threshold (first determination 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 determine 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 and clutch pressure in the brake control device 10 according to this embodiment. In Figure 3, the horizontal axis represents the percentage (unit: %) of the amount of brake operation (pedal operation amount) applied to the brake pedal 7a when the maximum operation amount is 100, 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. In Figure 3, the clutch pressure is shown by a solid line. The horizontal dashed line in Figure 3 indicates the clutch pressure level that can generate a braking force sufficient to stop the rotation of the winch drum 11. The vertical dashed line in Figure 3 indicates the operation amount threshold.

As shown in Figure 3, when the pedal operation amount is below the operation amount threshold, the clutch pressure is a value corresponding to the secondary pressure of the electromagnetic proportional pressure reducing valve 2, and gradually increases in accordance with 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 above a certain value. Due to its structure, the electromagnetic proportional pressure reducing valve 2 is good at controlling static pressure, but is not necessarily suited to operations such as rapidly increasing pressure or supplying large flow rates.

When the pedal operation amount exceeds the operation amount threshold, i.e., when the judgment 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. This connects the control pump 22 and the positive clutch chamber 6b of the brake unit 6 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 that can generate a braking force sufficient to stop the rotation of the winch drum 11. In this embodiment, the secondary pressure of the control pump 22 is a pressure greater 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 quickly increases from the secondary pressure of the electromagnetic proportional pressure reducing valve 2 to the secondary pressure of the control pump 22.

When the pedal operation amount is equal to or less than the operation amount threshold, the secondary pressure of the electromagnetic proportional pressure reducing valve increases proportionally with the increase in the pedal operation amount, and becomes a clutch pressure that can generate a braking force sufficient to stop the rotation of the winch drum 11 before the pedal operation amount reaches the operation amount threshold (a clutch pressure that can stop the suspended load from descending).

When the pedal operation amount increases gradually, as shown in Figure 3, the clutch pressure switches from the secondary pressure of the electromagnetic proportional pressure reducing valve 2, which has reached its maximum value, to the secondary pressure of the control pump 22. In this case, there is not much of a sudden increase in clutch pressure.

On the other hand, if 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 simultaneously with the start of 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 performed on the brake pedal 7a of the brake operating 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, a large flow rate of hydraulic oil can be quickly supplied to the positive clutch chamber 6b of the brake unit 6 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 Figure 4. Figure 4 is a flowchart showing an example of calculation processing by the controller 4.

When the brake control device 10 is set to the brake mode, i.e., when the mode selector valve 1 is in the second state, the controller 4 determines whether the operator has operated the mode selector switch 30 (step S1). When a free mode signal is input from the mode selector switch 30 (YES in step S1), the controller 4 controls the operation of the mode selector valve 1 to switch the state of the mode selector valve 1 from the second state to the first state (i.e., so that the solenoid of the mode selector valve 1 becomes energized), thereby switching the mode of the brake control device 10 to the free mode (step S2).

Next, the controller 4 determines whether the amount of braking applied to the brake pedal 7a of the brake operating 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 braking is equal to or less than the operation amount threshold (NO in step S3), the state of the mode switching valve 1 is maintained in the first state (step S5). Note that if the free mode is switched to the brake mode while the processes of steps S3 and S5 are being repeated, the controller 4 ends the process shown in FIG. 4.

On the other hand, if the amount of brake operation exceeds the operation amount threshold (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 (i.e., so that the solenoid of the mode switching valve 1 becomes de-energized) (step S4).

Figure 5 is a graph showing an example of the relationship between the operating speed of the brake operation and the clutch pressure in a brake control device 10 according to Modification 1 of this embodiment. The brake control device 10 according to Modification 1 uses different judgment conditions than the brake control device 10 shown in Figure 3. The 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 Figure 2. Modification 1 will be described below with reference to Figures 2 and 5.

In Modification 1, the determination condition is a condition (second determination condition) in which the operation speed of the brake operation exceeds a preset operation speed threshold. The operation speed during sudden braking (i.e., the pedal operation speed at which the brake pedal 7a is depressed during sudden braking) is typically high. Therefore, in Modification 1, the controller 4 can determine whether a sudden braking operation has been applied to the brake pedal 7a of the brake operating device 7 by comparing the operation speed of the brake operation with the operation speed threshold. Specifically, for example, even if the operator intends to perform a braking operation that exceeds the operation amount threshold, the brake pedal 7a may not actually be sufficiently depressed. In this case, if the determination condition is the first determination condition (a condition using the operation amount threshold), the state of the mode switching valve 1 remains in the first state. On the other hand, in Modification 1, the determination condition is the second determination condition (a condition using the operation speed threshold). Therefore, 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 mode switching valve 1 switches from the first state to the second state. Therefore, the second judgment condition in Modification 1 is a condition that more closely corresponds to the braking operation (fast pedal operation) that operators often perform when they want to apply the brakes instantly. Therefore, Modification 1 can more appropriately determine whether a sudden braking operation has been applied.

In this variant 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.

In Figure 5, the horizontal axis represents the operating speed of the brake (pedal operating speed), 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 in Figure 5 represents the state (first state or second state) of the mode switching valve 1. The vertical dashed line in Figure 5 represents the operating speed threshold.

As shown in Figure 5, when the pedal operation speed is equal to or less than the operation speed threshold, the clutch pressure becomes 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.

On the other hand, if the pedal operation speed exceeds the operation speed threshold, i.e., if the second judgment condition is satisfied, the controller 4 controls the operation of the mode change valve 1 so that the mode change 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. 5, when the state of the mode change valve 1 switches from the first state to the second state, the clutch pressure quickly 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).

Figure 6 is a diagram showing the hydraulic circuit and controller 4 of a 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 further includes a switching valve 12 (emergency braking-only switching valve 12) and a check valve 8. The other configuration of the brake control device 10 according to Modification 2 is similar to that of the brake control device 10 shown in Figure 2. The emergency braking-only switching valve 12 is an example of a switching valve (second switching valve) in the present disclosure, and is located between the control pump 22 and the brake unit 6.

In the brake control device 10 shown in FIG. 2, the mode change valve 1 has the dual role of switching between free mode and brake mode, and of quickly supplying the secondary pressure of the control pump 22 to the positive clutch chamber 6b of the brake control device 10 when an emergency braking operation is performed on the brake pedal 7a. Meanwhile, in this variant example 2, these two roles are shared between the mode change valve 1 and the emergency braking switch valve 12. That is, the mode change valve 1 has the role of switching between free mode and brake mode, and the emergency braking switch valve 12 has the role of quickly supplying the secondary pressure of the control pump 22 to the positive clutch chamber 6b of the brake control device 10 when an emergency braking operation is performed on the brake pedal 7a.

The emergency braking switching valve 12 is an electromagnetic switching valve that is even more responsive to command signals from the controller 4 than the mode switching valve 1. Because of its role in switching between free mode and brake mode, the spool and coil sizes of the mode switching valve 1 are larger than those of the emergency braking switching valve 12. The emergency braking switching valve 12 has a structure specialized for responding to emergency braking, and is even more responsive to command signals from the controller 4 than the mode switching valve 1. By arranging these switching valves 1 and 12 in parallel in the hydraulic circuit, the switching operation between free mode and brake mode by the mode switching valve 1 and the rapid response to emergency braking are even smoother than those of the brake control device shown in Figure 2.

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 hydraulic oil to flow from the switching valve 12 toward the positive clutch chamber 6b, while preventing hydraulic oil from flowing from the positive clutch chamber 6b toward the switching valve 12. When the solenoid of the switching valve 12 is in a de-energized state (left position, first state in Figure 6), the switching valve 12 is connected to the tank 27. When the solenoid of the switching valve 12 is in an energized state (right position, second state in Figure 6), 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 going through the electromagnetic proportional pressure reducing valve 2. The check valve 8 prevents the pressure in the positive clutch chamber 6b from becoming the pressure in the tank 27 by preventing the positive clutch chamber 6b from communicating with the tank 27 when the switching valve 12 is in a de-energized state.

When the determination condition is met, 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 going through the electromagnetic proportional pressure reducing valve 2. As a result, when a sudden braking operation is applied to the brake pedal 7a of the brake operation 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, the brake response time is further reduced when a sudden braking operation is performed. Note that in variant 2, the determination condition may be either the first determination condition or the second determination condition.

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

(A) Regarding the Determination Conditions In the above embodiment, the determination condition is that the amount of brake operation exceeds an operation amount threshold (first determination condition), and in Modification Example 1 of the above embodiment, the determination condition is that the operation speed of the brake operation exceeds an operation speed threshold (second determination condition). However, the determination condition according to the present disclosure may include both the first determination condition and the second determination condition, and the controller may be configured to switch the switching valve so that the brake unit is connected to the hydraulic pump bypassing the electromagnetic proportional pressure reducing valve when the first determination condition and the second determination condition are satisfied. Specifically, in the hydraulic circuit of FIG. 2 , 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 when the first determination condition and the second determination condition are satisfied. Alternatively, in the hydraulic circuit of FIG. 6 , the controller may control the operation of the emergency braking switching valve 12 so that the emergency braking switching valve 12 switches from the first state to the second state when the first determination condition and the second determination condition are satisfied. When the determination conditions include both the first and second determination conditions, it is possible to more appropriately determine whether or not a sudden braking operation has been applied compared to when the determination conditions include the second determination condition. Specifically, for example, when the load 106 is free-falling due to its own weight, the operator may apply the brakes to reduce the falling speed of the load 106 rather than to suddenly apply the brakes to stop the load 106 from falling. In such a case, for example, even if the amount of braking does not exceed the operation amount threshold (even if the first determination condition is not satisfied), the state of the switching valve is switched from the first state to the second state when the operating speed of the braking operation exceeds the operating speed threshold (when the second determination condition is satisfied). In this case, sudden braking is applied to stop the load 106 from falling, and this sudden braking may not be to the operator's liking. On the other hand, when the determination conditions include both the first and second determination conditions, the state of the switching valve is switched from the first state to the second state only when both the first and second determination conditions are satisfied. This allows the determination of whether or not a sudden braking operation has been applied to be closer to the sense of the operator.

(B) Regarding the switching valve In the specific example described above, the mode switching valve 1 and the emergency braking switching valve 12 are each 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, at least one of the mode switching valve 1 and the emergency braking switching valve 12 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.

DESCRIPTION OF SYMBOLS 1: Mode switching valve 2: Electromagnetic proportional pressure reducing valve 3: Emergency brake 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 rotating body 104: Boom R: Rope

Claims (5)

A brake control device,
A hydraulic pump,
a brake unit that receives hydraulic oil discharged from the hydraulic pump and generates a braking force on the winch drum;
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 brake unit in accordance with the amount of brake operation;
a mode switching valve interposed between the hydraulic pump and the brake unit , for switching the mode of the brake control device between a free mode in which the braking force can be adjusted in accordance with the amount of brake operation and a brake mode in which the winch drum can be rotated by the power of a winch motor; and
a controller that switches the mode switching valve when a preset determination condition is satisfied in order to determine that a sudden braking operation has been applied to the operating device , so that the mode of the brake control device is switched from the free mode to the brake mode and the brake unit is connected to the hydraulic pump, bypassing the electromagnetic proportional pressure reducing valve. A brake control device,
A hydraulic pump,
a brake unit that receives hydraulic oil discharged from the hydraulic pump and generates a braking force on the winch drum;
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 brake unit in accordance with the amount of 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 predetermined determination condition is satisfied in order to determine that an emergency braking operation has been applied to the operating device;
a mode switching valve for switching the mode of the brake control device between a free mode and a brake 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 is an electromagnetic switching valve having a higher responsiveness to a command signal from the controller than the mode switching valve. 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. The brake control device according to any one of claims 1 to 3 , 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 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.