Swing control device, work machine, and swing control method

Abstract

This technology provides a way to suppress the complexity of the system configuration required to stop the upper rotating body while it is rotating in neutral free mode. [Solution] The directional switching spool 51A of the slewing control valve 50 is displaceable between a neutral free position 51N, a left slewing position 51L, and a right slewing position 51R, forming a passage for circulating hydraulic fluid between the slewing motor 40 and the slewing control valve 20. The brake spool 52A of the slewing control valve 50 is displaceable between a neutral brake position 52N, which applies brake pressure to the slewing motor 40, and a release position 52X, which releases the brake pressure. The slewing control device 20 includes a controller 30 configured to output a brake command to the brake spool control valve 62 so that, in the neutral free mode, the brake spool 52A moves from the release position 52X to the neutral brake position 52N, regardless of the slewing direction of the upper slewing body 10 of the work machine 1.

Description

Technical Field

[0001] This disclosure relates to technologies for working machines such as cranes.

Background Art

[0002] Patent Document 1 discloses a swing control device. This swing control device includes a hydraulic pump, a swing hydraulic motor driven by the discharge oil from the hydraulic pump to swing a swing body, a control valve having a neutral free position and inserted in an oil passage between the hydraulic pump and the swing hydraulic motor, a swing operation device that operates the control valve to control the rotation speed and rotation direction of the swing hydraulic motor and enables the rotation of the swing body due to inertia by setting the neutral free position so that no hydraulic braking force is generated in the return oil passage of the swing hydraulic motor, a swing state detection device that detects the swing state of the swing body, a swing limit position setting device that sets a swing limit position of the swing body, and when it is determined based on the detection result of the swing state detection device that the swing body is in a swing state approaching the swing limit position, a braking hydraulic device that operates the control valve so that a hydraulic braking force is generated in the return oil passage of the swing hydraulic motor even when the control valve is in the neutral free position, and a control device that controls the braking hydraulic device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The hydraulic braking system described in Patent Document 1 includes two proportional pressure reducing valves (54, 55) that control the pilot pressure oil to the control valve so that the slewing body rotates in the opposite direction to the direction of rotation. In the hydraulic braking system described in Patent Document 1, two valves are required, namely a valve (proportional pressure reducing valve) for braking the rotation of the slewing hydraulic motor when the slewing body is rotating to the left and a valve (proportional pressure reducing valve) for braking the rotation of the slewing hydraulic motor when the slewing body is rotating to the right, which tends to make the system configuration of the work machine complex.

[0005] This disclosure aims to provide a technology that can suppress the complexity of the system configuration required to stop the upper rotating body that is rotating in neutral free mode. [Means for solving the problem]

[0006] The first aspect of the slewing control device is a control device for controlling a work machine, the work machine comprising a hydraulic pump for discharging hydraulic fluid, a slewing motor that operates upon receiving the supply of hydraulic fluid, a mode switching valve for switching between a neutral brake mode and a neutral free mode, a slewing control valve having a direction switching spool and a brake spool, and a brake spool control valve for controlling the operation of the brake spool, wherein the direction switching spool is displaceable to a neutral free position, a left slewing position, and a right slewing position, forming a passage for circulating the hydraulic fluid between the slewing motor and the slewing control valve, the brake spool is displaceable to a neutral brake position for applying brake pressure to the slewing motor and a release position for releasing the brake pressure, and the slewing control device comprises a controller configured to output a brake command to the brake spool control valve so that, in the neutral free mode, the brake spool moves from the release position to the neutral brake position regardless of the direction of rotation of the upper slewing body of the work machine.

[0007] In this first embodiment, in the neutral free mode, the movement of the brake spool from the release position to the neutral brake position is controlled by the brake spool control valve, regardless of the rotation direction of the upper slewing body. Therefore, in this first embodiment, the work machine does not need to have the two valves for braking left and right rotations of the slewing body as in the conventional system, and the rotation of the slewing motor can be stopped by the brake spool control valve in the neutral free mode. This helps to prevent the system configuration of the work machine from becoming too complex.

[0008] The slewing control device according to the second embodiment preferably further comprises the following configuration in addition to the slewing control device according to the first embodiment. That is, in the slewing control device according to the second embodiment, the controller is preferably configured to output the brake command when a preset slewing stop condition is met for determining whether or not it is necessary to stop the slewing of the upper slewing body. A specific example is as follows.

[0009] For example, if the work machine is equipped with an operator status detector such as a dead man's switch, the slewing stop condition may include the condition that the controller receives a predetermined signal from the operator status detector. Also, if the work machine is equipped with a slewing angle sensor that acquires the slewing angle of the upper slewing body, the slewing stop condition may include a condition based on the slewing angle of the upper slewing body. Specifically, the slewing stop condition may include the condition that the slewing angle reaches a predetermined value. Furthermore, the slewing stop condition may include, for example, the condition that a slewing stop signal is input to the controller from an external device which is a different device from the work machine.

[0010] The work machine according to the third embodiment comprises the hydraulic pump, the slewing motor, the mode switching valve, the slewing control valve, the brake spool control valve, and the slewing control device according to the first or second embodiment.

[0011] The work machine according to the fourth embodiment preferably further comprises the following configuration in addition to the work machine according to the third embodiment. That is, in the work machine according to the fourth embodiment, the brake spool is displaceable to the neutral brake position, the left turn release position, and the right turn release position, and in the neutral free mode, regardless of the turning direction of the upper rotating body, it is preferable that either the left turn release position or the right turn release position is used as the release position.

[0012] In this fourth embodiment, in the neutral free mode, the brake spool may be positioned in the release position in both cases when the upper rotating body is rotated to the left and when it is rotated to the right, and may move from the release position to the neutral brake position when the rotation of the upper rotating body is stopped, that is, when the brake command is input from the controller to the brake spool control valve.

[0013] On the other hand, in this fourth embodiment, in the neutral brake mode, the brake spool may be configured to be positioned in the left rotation release position when the upper rotating body is rotated to the left, in the right rotation release position when the upper rotating body is rotated to the right, and to move from the left rotation release position or the right rotation release position to the neutral brake position when the rotation of the upper rotating body is stopped.

[0014] The work machine according to the fifth embodiment preferably further comprises the following configuration in addition to the work machine according to the third or fourth embodiment. That is, the work machine according to the fifth embodiment further comprises an actuator for receiving left turn command operations and right turn command operations, wherein the actuator is configured to output an operating pressure corresponding to the left turn command operation and the right turn command operation, respectively, and in the neutral brake mode, the directional switching spool and the brake spool are configured to be displaced according to the operating pressure, and in the neutral free mode, the directional switching spool is configured to be displaced according to the operating pressure, while the brake spool is configured to be displaced according to the brake spool operating pressure output from the brake spool control valve.

[0015] In this fifth embodiment, in the neutral free mode, when the actuator receives the left turn command operation or the right turn command operation, the brake spool may be configured to be positioned in the release position in accordance with the brake spool operating pressure output from the brake spool control valve. Furthermore, in the neutral free mode, when the rotation of the upper rotating body is stopped, that is, when the brake command is input from the controller to the brake spool control valve, the brake spool control valve may be configured to output a brake spool operating pressure corresponding to the brake command, and the brake spool may be displaced from the release position to the neutral brake position in accordance with the brake spool operating pressure.

[0016] On the other hand, in this fifth embodiment, in the neutral brake mode, when the actuator receives the left turn command operation, the brake spool moves from the neutral brake position to the left turn release position; when the actuator receives the right turn command operation, the brake spool moves from the neutral brake position to the right turn release position; and when the actuator is returned to the neutral position, the brake spool is displaced from the left turn release position or the right turn release position to the neutral brake position.

[0017] The work machine according to the sixth embodiment preferably further comprises the following configuration in addition to the work machine according to the fifth embodiment. That is, the work machine according to the sixth embodiment further comprises a slewing stop control valve that reduces the operating pressure in response to a slewing stop command input from the controller, and in the neutral free mode, the controller may be configured to input the slewing stop command to the slewing stop control valve to displace the direction switching spool to the neutral free position when a preset slewing stop condition is met for determining whether or not it is necessary to stop the slewing of the upper slewing body, and to input the brake command to the brake spool control valve to displace the brake spool from the release position to the neutral brake position.

[0018] The work machine according to the seventh embodiment preferably further comprises the following configuration in addition to the work machine according to any one of the third to sixth embodiments. That is, in the work machine according to the seventh embodiment, it is preferable that the area of ​​the meter-in opening and the area of ​​the meter-out opening are the same when the brake spool is in the release position.

[0019] In this seventh embodiment, since the area of ​​the meter-in opening and the area of ​​the meter-out opening are the same when the brake spool is in the release position, it is possible to suppress a large difference in the deceleration characteristics of the slewing motor regardless of the direction of rotation of the upper slewing body, i.e., the direction of rotation of the slewing motor.

[0020] The eighth aspect of the slewing control method is a control method using the slewing control device according to the first or second aspect, or a control method using the work machine according to any one of the third to seventh aspects, wherein the controller of the slewing control device outputs the brake command to the brake spool control valve so that, in the neutral free mode, the brake spool moves from the release position to the neutral brake position, regardless of the slewing direction of the upper slewing body.

[0021] In this eighth aspect, in the neutral free mode, the operation of the brake spool moving from the release position to the neutral brake position is controlled by the brake spool control valve regardless of the turning direction of the upper slewing body. Therefore, in this eighth aspect, the work machine may not include the two valves for braking the left turn and the right turn of the slewing body as in the conventional art, and the turning of the slewing motor can be stopped by the brake spool control valve in the neutral free mode. Thereby, it is possible to suppress the complication of the system configuration of the work machine.

Advantages of the Invention

[0022] According to the present disclosure, a technique is provided that can suppress the complication of the system configuration for stopping the upper slewing body that is turning in the neutral free mode.

Brief Description of the Drawings

[0023] [Figure 1] It is a side view of a work machine according to an embodiment. [Figure 2] It is a diagram showing a turning control device according to an embodiment and main components of a hydraulic circuit included in the work machine. [Figure 3] It is a graph showing an example of characteristics of a turning control valve of the work machine. [Figure 4] It is a graph showing an example of the change over time of a brake command, the change over time of the outlet pressure of a turning motor, and the change over time of a turning speed in turning stop control by the controller. [Figure 5] It is a flowchart showing an example of arithmetic processing performed by a controller of the turning control device. [Figure 6] It is a flowchart showing an example of arithmetic processing performed by a controller of the turning control device. [Figure 7] It is a diagram showing a turning control device according to a modification of the embodiment and main components of a hydraulic circuit included in the work machine.

Modes for Carrying Out the Invention

[0024] Embodiments of this disclosure will be described with reference to the drawings.

[0025] Figure 1 is a side view of the work machine 1 according to this embodiment. The work machine 1 is a crane. Although Figure 1 shows directions "up," "down," "front," and "rear," these directions are shown for convenience to explain the structure of the work machine 1 according to this embodiment and do not limit the manner in which the work machine according to this disclosure is used.

[0026] The work machine 1 comprises a lower body 11, an upper slewing body 10, and a luffing member 13. The lower body 11 shown in Figure 1 is equipped with a travel device and is configured to be able to move on the ground G. The upper slewing body 10 is supported by the lower body 11 so as to be able to rotate around a vertical rotation axis. The upper slewing body 10 includes a slewing frame that constitutes the base portion of the upper slewing body 10, and a cab 12 supported at the front of this slewing frame. Inside the cab 12 are a driver's seat and controls 70, which will be described later.

[0027] The luffing member 13 is supported on the upper slewing body 10 so as to be able to luff. The base end 13S of the luffing member 13 is rotatably attached to the upper slewing body 10. The luffing member 13 is composed of a boom. The luffing member 13 may include a boom and a jib (not shown) supported at the tip of the boom. In the specific example shown in Figure 1, the luffing member 13 is a so-called lattice-type luffing member. The luffing member 13 may include a plurality of boom members 13A, 13B, 13C. The luffing member 13 may also be a telescopic-type luffing member. A sheave 132 is provided at the tip of the luffing member 13.

[0028] The work machine 1 comprises an upper spreader 131, a lower spreader 133, a compression member 14 and a tension member 15 that constitute a gantry, a luffing winch 16, and a luffing rope 17.

[0029] The upper spreader 131 and the lower spreader 133 each have multiple sheaves. The upper spreader 131 is also connected to the tip of the luffing member 13 by a boom guy line 13G (guy link).

[0030] The compression member 14 is a support column extending upward and backward from approximately the center of the upper slewing body 10. The tension member 15 is a support column extending upward from the rear of the upper slewing body 10 and is connected to the upper end of the compression member 14. The tip of the gantry is provided with a gantry sheave 141.

[0031] The luffing rope 17 is pulled out from the luffing winch 16, placed on the gantry sheave 141 of the gantry, and then looped around multiple times between the sheaves of the lower spreader 133 and the upper spreader 131. The luffing winch 16 raises and lowers the luffing member 13 by winding in and unwinding the luffing rope 17.

[0032] The work machine 1 is equipped with a main hoisting winch 18 for hoisting and lowering a suspended load. A main hook 19F for hoisting a load is attached to the end portion 19A of the main hoisting rope 19 that is pulled out from the main hoisting winch 18. The main hoisting rope 19 is stretched between a sheave 132 at the tip of the luffing member 13 and a sheave of a sheave block (not shown) provided on the main hook. When the main hoisting winch 18 winds up or unwinds the main hoisting rope 19, the main hook 19F connected to the end portion 19A of the rope hanging down from the tip of the luffing member 13 rises and falls. Note that the structure of the work machine in this disclosure is not limited to the work machine 1 shown in Figure 1.

[0033] Figure 2 shows the slewing control device 20 according to the embodiment and the main components of the hydraulic circuit provided in the work machine 1. The slewing control device 20 controls the operation of the work machine 1.

[0034] As shown in Figure 2, the work machine 1 comprises a hydraulic pump 90 that discharges hydraulic fluid, a slewing motor 40 that operates upon the supply of the hydraulic fluid, a mode switching valve 60 that switches the slewing mode, which is a control mode for slewing in the work machine 1, between a neutral brake mode and a neutral free mode, a slewing control valve 50 having a directional switching spool 51A and a brake spool 52A, and a brake spool control valve 62 that controls the operation of the brake spool 52A.

[0035] The neutral brake mode is a mode in which the brake spool 52A is displaced in response to a turning command operation given to the actuator 70. The neutral free mode is a mode in which the brake spool 52A is positioned in the release position 52X regardless of the turning command operation given to the actuator 70. Hereinafter, the release position 52X in which the brake spool 52A is positioned in the neutral free mode may be referred to as the specific release position 52X.

[0036] The setting of the slewing mode may be performed, for example, on the operation screen of the display unit 94 (e.g., a touch panel). Specifically, the operator may perform an input operation to select one of several modes from the operation screen displayed on the display unit 94 before starting work or during work. When the display unit 94 receives an input operation for mode selection, it inputs a mode signal corresponding to the selected mode to the controller 30. The controller 30 sets the slewing mode to the mode corresponding to the input mode signal and stores it. Alternatively, the setting of the slewing mode may be performed, for example, by an input operation by the operator to an input unit 100, which is a device separate from the display unit 94.

[0037] The directional control spool 51A is displaceable to a neutral free position 51N which forms a passage for circulating the hydraulic fluid between the slewing motor 40 and the slewing control valve 50, a left slewing position 51L which forms a passage for supplying the hydraulic fluid discharged from the hydraulic pump 90 to the slewing motor 40 and causing the upper slewing body to slewing left, and a right slewing position 51R which forms a passage for supplying the hydraulic fluid discharged from the hydraulic pump 90 to the slewing motor 40 and causing the upper slewing body to slewing right. In other words, the directional control spool 51A is the spool of a three-position directional control valve.

[0038] The brake spool 52A is displaceable between a neutral brake position 52N that applies brake pressure to the swing motor 40 and a specific release position 52X that releases the brake pressure. The brake spool 52A may be a spool that is displaceable only between the neutral brake position 52N and the specific release position 52X, but as will be described later, it may also be a spool of a three-position switching valve that is displaceable between the neutral brake position 52N and the left swing release position 52L, and also displaceable between the neutral brake position 52N and the right swing release position 52R.

[0039] The rotation control device 20 according to this embodiment has the following first and second features.

[0040] [Feature 1] The slewing control device 20 includes a controller 30. In the neutral free mode, the controller 30 is configured to output a brake command to the brake spool control valve 62 so that the brake spool 52A moves from a specific release position 52X to a neutral brake position 52N, regardless of the slewing direction of the upper slewing body 10 of the work machine 1.

[0041] In this embodiment, in the neutral free mode, the operation of the brake spool 52A moving from a specific release position 52X to a neutral brake position 52N is controlled by the brake spool control valve 62, regardless of the rotation direction of the upper rotating body 10. That is, in the neutral free mode, the rotation of the rotating motor 40 can be stopped by the brake spool control valve 62. This helps to prevent the system configuration of the work machine 1 from becoming complicated.

[0042] [Second characteristic] The controller 30 is configured to output the brake command when the predetermined rotation stop conditions are met in order to determine whether or not it is necessary to stop the rotation of the upper rotating body 10. A specific example is as follows.

[0043] For example, if the work machine 1 is equipped with an operator status detector 99, such as a dead man switch system described later, the slewing stop condition may include the condition that the controller 30 receives a predetermined signal from the operator status detector 99. That is, the controller 30 may output the brake command when it receives a predetermined signal from the operator status detector 99. Specifically, the operator status detector 99 may be configured to input the predetermined signal to the controller 30 when it detects that the operator's state is such that the slewing of the upper slewing body 10 should be stopped.

[0044] Furthermore, if the work machine 1 is equipped with a slewing angle sensor 98 that acquires the slewing angle of the upper slewing body 10, the slewing stop condition may include a condition based on the slewing angle of the upper slewing body 10. Specifically, the slewing stop condition may include a condition that the slewing angle reaches a predetermined value. That is, the controller 30 may output the brake command when the slewing angle input from the slewing angle sensor 98 reaches a predetermined value.

[0045] Furthermore, the slewing stop condition may include, for example, a condition in which a slewing stop signal is input to the controller 30 from an external device 200, which is a different device from the work machine 1. In this case, the external device 200 and the work machine 1 may be configured to communicate with each other via a network 300. When a person involved in the work, such as a supervisor monitoring the work performed by the work machine 1, recognizes a situation in which the operation of the work machine 1 should be stopped, they may perform an input operation to the external device 200 to stop the operation of the work machine 1, and the external device 200 may transmit a slewing stop signal corresponding to the input operation to the work machine 1 via a network 300, such as the internet or a mobile phone network. When the controller 30 receives the slewing stop signal, it may output the brake command.

[0046] The slewing control device 20 and the work machine 1 according to this embodiment have the following third to eighth features.

[0047] [Third characteristic] The work machine 1 includes a hydraulic pump 90, a slewing motor 40, a mode switching valve 60, a slewing control valve 50, a brake spool control valve 62, and a slewing control device 20. As shown in Figure 2, the slewing control device 20 according to this embodiment is provided on the work machine 1.

[0048] However, the slewing control device 20 does not necessarily have to be provided on the work machine 1, and may, for example, be provided on an external device 200. In this case, when the person in charge of the work recognizes a situation in which the operation of the work machine 1 should be stopped, they perform an input operation to the external device 200 to stop the operation of the work machine 1, and the controller 30 of the slewing control device 20 in the external device 200 may output the brake command when it receives a slewing stop signal corresponding to the input operation. The external device 200 may transmit the brake command to the work machine 1 via the network 300. The machine controller (not shown) provided on the work machine 1 receives the brake command. In the neutral free mode, the machine controller may input the brake command to the brake spool control valve 62 so that the brake spool 52A moves from a specific release position 52X to a neutral brake position 52N, regardless of the slewing direction of the upper slewing body 10 of the work machine 1.

[0049] [Fourth characteristic] The brake spool 52A is displaceable to a neutral brake position 52N, a left-turn release position 52L, and a right-turn release position 52R. In the neutral free mode, regardless of the rotation direction of the upper rotating body 10, either the left-turn release position 52L or the right-turn release position 52R is used as the specific release position 52X. That is, in the neutral free mode, only the predetermined release position among the left-turn release position 52L and the right-turn release position 52R is used as the specific release position 52X, regardless of the rotation direction of the upper rotating body 10. In the specific example shown in Figure 2, the left-turn release position 52L is used as the specific release position 52X. Specifically, it is as follows.

[0050] As described above, the neutral brake position 52N is the position in which brake pressure is applied to the swing motor 40, while the left swing release position 52L and the right swing release position 52R are positions in which the brake pressure applied to the swing motor 40 is released.

[0051] In this embodiment, in the neutral free mode, the brake spool 52A is configured to be positioned at the left-turn release position 52L, which is the specific release position 52X, in both cases when the upper rotating body 10 is rotated to the left and when it is rotated to the right. In the neutral free mode, the brake spool 52A is configured to move from the specific release position 52X to the neutral brake position 52N when the rotation of the upper rotating body 10 is stopped, that is, when the brake command is input from the controller 30 to the brake spool control valve 62.

[0052] On the other hand, in the neutral brake mode, the brake spool 52A is configured to be positioned at the left-turn release position 52L when the upper slewing body 10 is turned left, at the right-turn release position 52R when the upper slewing body 10 is turned right, and to move from the left-turn release position 52L or the right-turn release position 52R to the neutral brake position 52N when the rotation of the upper slewing body 10 is stopped.

[0053] Figure 3 is a graph showing an example of the characteristics of the swivel control valve 50. Figure 3 shows the characteristics of the M / I opening area and M / O opening area when the brake spool 52A is displaced in the range between the neutral brake position 52N and the left swivel release position 52L. As shown in Figure 3, the brake spool 52A can adjust the area of ​​the meter-in opening (M / I opening area) that controls the meter-in side pressure of the swivel motor 40, and the area of ​​the meter-out opening (M / O opening area) that controls the meter-out side pressure of the swivel motor 40. As the brake spool 52A moves from the neutral brake position 52N (minimum displacement position) towards the left swivel release position 52L (maximum displacement position), the M / I opening area and M / O opening area gradually increase. The "pilot pressure" on the right vertical axis in Figure 3 is the pilot pressure that determines the stroke position of the brake spool 52A, i.e., the pilot pressure input to the left swivel pilot port 52a or the right swivel pilot port 52b, which will be described later. As shown in Figure 3, once the pilot pressure is determined, the stroke position, M / I opening area, and M / O opening area of ​​the brake spool 52A are determined. This pilot pressure increases or decreases as indicated by the solid line (upward sloping solid line) pointed to by the arrow extending from the label "Spring Characteristics" in Figure 3.

[0054] Although not shown in the diagram, the characteristics of the M / I opening area and M / O opening area when the brake spool 52A is displaced in the range between the neutral brake position 52N and the right turn release position 52R are the same as those shown in Figure 3.

[0055] [Fifth characteristic] The work machine 1 further includes an actuator 70 that receives left turn command operations and right turn command operations. The actuator 70 is configured to output an operating pressure corresponding to the left turn command operation and the right turn command operation, respectively. In the neutral brake mode, the directional switching spool 51A and the brake spool 52A are configured to be displaced in accordance with the operating pressure output from the actuator 70. In the neutral free mode, the directional switching spool 51A is configured to be displaced in accordance with the operating pressure output from the actuator 70, while the brake spool 52A is configured to be displaced in accordance with the brake spool operating pressure output from the brake spool control valve 62.

[0056] In this embodiment, in the neutral free mode, when the operator 70 receives the left turn command operation or the right turn command operation, the brake spool 52A is configured to be positioned at a specific release position 52X in accordance with the brake spool operating pressure output from the brake spool control valve 62. In the neutral free mode, when the rotation of the upper rotating body 10 is to be stopped, that is, when the brake command is input from the controller 30 to the brake spool control valve 62, the brake spool control valve 62 outputs a brake spool operating pressure corresponding to the brake command, and the brake spool 52A is configured to be displaced from the specific release position 52X to the neutral brake position 52N in accordance with the brake spool operating pressure.

[0057] On the other hand, in the neutral brake mode, when the actuator 70 receives the left turn command, the brake spool 52A moves from the neutral brake position 52N to the left turn release position 52L. When the actuator 70 receives the right turn command, the brake spool 52A moves from the neutral brake position 52N to the right turn release position 52R. When the actuator 70 is returned to the neutral position, the brake spool 52A is configured to be displaced from the left turn release position 52L or the right turn release position 52R back to the neutral brake position 52N.

[0058] [Sixth characteristic] The work machine 1 further includes a swivel stop control valve 80 that reduces the operating pressure in response to a swivel stop command input from the controller 30. In the neutral free mode, when the swivel stop condition is met, the controller 30 is configured to input the swivel stop control valve 80 with the swivel stop command to displace the directional switching spool 51A to the neutral free position 51N, and to input the brake command to the brake spool control valve 62 to displace the brake spool 52A from the specific release position 52X to the neutral brake position 52N. The swivel stop control valve 80 may include, for example, a left swivel pressure reducing valve 81 and a right swivel pressure reducing valve 82, which will be described later. The left swivel pressure reducing valve 81 and the right swivel pressure reducing valve 82 will be described later.

[0059] [Characteristic 7] As shown in Figure 3, when the brake spool 52A is positioned in a specific release position 52X, the area of ​​the meter-in opening (maximum opening area) and the area of ​​the meter-out opening (maximum opening area) are the same (M / I opening area = M / O opening area).

[0060] In this embodiment, since the area of ​​the meter-in opening and the area of ​​the meter-out opening are the same when the brake spool 52A is positioned in a specific release position 52X, it is possible to suppress a large difference in the deceleration characteristics of the slewing motor 40 regardless of the direction of rotation of the upper slewing body 10, i.e., the direction of rotation of the slewing motor 40.

[0061] Furthermore, as shown in Figure 3, when the brake spool 52A is positioned in the neutral brake position 52N, the area of ​​the meter-in opening (minimum opening area) and the area of ​​the meter-out opening (minimum opening area) may be the same (M / I opening area = M / O opening area). Also, when the brake spool 52A is positioned in the neutral brake position 52N, the area of ​​the meter-in opening (minimum opening area) may be slightly larger than the area of ​​the meter-out opening (minimum opening area).

[0062] [Characteristic 8] The slewing control method according to this embodiment is a control method using a slewing control device 20, and includes the controller 30 of the slewing control device 20 outputting the brake command to the brake spool control valve 62 so that, in the neutral free mode, the brake spool 52A moves from a specific release position 52X to a neutral brake position 52N, regardless of the slewing direction of the upper slewing body 10. This slewing control method makes it possible to suppress the complexity of the system configuration of the work machine 1.

[0063] The main features of the slewing control device 20, the work machine 1, and the slewing control method according to this embodiment are as described above. The embodiment will be described in more detail below, but the slewing control device, work machine, and slewing control method according to this disclosure are not limited to the following specific examples.

[0064] First, let's explain some specific examples of the components that make up the hydraulic circuit shown in Figure 2.

[0065] The hydraulic pump 90 is driven by a power source (not shown) and is driven to draw in and discharge hydraulic fluid from a tank. The power source may be, for example, an engine or a power supply device. If the power source is a power supply device, an electric motor may be interposed between the power supply device and the hydraulic pump 90. The power supply device may be, for example, a battery, a fuel cell, or a generator.

[0066] The slewing motor 40 is a hydraulic motor and has an output shaft connected to the upper slewing body 10 via a reduction mechanism 93. The slewing motor 40 operates by receiving hydraulic fluid discharged by the hydraulic pump 90 to rotate the upper slewing body 10 in a slewing direction corresponding to the flow direction of the hydraulic fluid at a speed corresponding to the flow rate of the hydraulic fluid. Specifically, the slewing motor 40 has a left slewing port 40a and a right slewing port 40b. When hydraulic fluid is supplied to the left slewing port 40a, the slewing motor 40 operates to rotate the upper slewing body 10 to the left while discharging the hydraulic fluid from the right slewing port 40b. When hydraulic fluid is supplied to the right slewing port 40b, the slewing motor 40 operates to rotate the upper slewing body 10 to the right while discharging the hydraulic fluid from the left slewing port 40a.

[0067] The slewing control valve 50 is interposed between the hydraulic pump 90 and the slewing motor 40 and has the function of changing the flow direction and flow rate of the hydraulic fluid supplied from the hydraulic pump 90 to the slewing motor 40 by operating from a neutral state where no pilot pressure is supplied, and conversely, applying brake pressure to the slewing motor 40 when it returns to the neutral state.

[0068] The swivel control valve 50 has a directional control valve section 51 and a brake valve section 52 arranged in series with respect to each other. As shown in Figure 2, the swivel control valve 50 may be configured so that a common pilot pressure is supplied to the directional control valve section 51 and the brake valve section 52 when the swivel mode is the neutral brake mode. The directional control valve section 51 may be located upstream of the brake valve section 52 in the flow direction of the hydraulic fluid discharged by the hydraulic pump 90.

[0069] The directional control valve section 51 may be composed of a pilot-operated three-position directional control valve. The directional control valve section 51 has a directional control spool 51A and a flow rate adjustment function that changes the flow rate of the hydraulic fluid according to the stroke of the directional control spool 51A. The directional control valve section 51 has a left-turning pilot port 51a and a right-turning pilot port 51b.

[0070] The direction switching spool 51A is displaceable to a neutral free position 51N which forms a passage for circulating hydraulic fluid between the slewing motor 40 and the slewing control valve 50, a left slewing position 51L which forms a passage for supplying hydraulic fluid to the left slewing port 40a of the slewing motor 40, and a right slewing position 51R which forms a passage for supplying hydraulic fluid to the right slewing port 40b of the slewing motor 40.

[0071] The directional control spool 51A of the directional control valve section 51 is held in a neutral free position 51N when no pilot pressure is supplied to either the left-turn pilot port 51a or the right-turn pilot port 51b. When the directional control spool 51A is in the neutral free position 51N, the directional control valve section 51 forms an oil passage for the hydraulic fluid to circulate, allowing the slewing motor 40 to rotate freely and the upper slewing body 10 to rotate by inertia. In other words, the directional control valve section 51 is a neutral free type directional control valve.

[0072] The directional control valve section 51 is configured such that when pilot pressure is supplied to the left-turn pilot port 51a, the directional control spool 51A is displaced from the neutral free position 51N to the left-turn position 51L by a stroke corresponding to the magnitude of the pilot pressure. When the directional control spool 51A is in the left-turn position 51L, the directional control valve section 51 forms an oil passage having an opening area corresponding to the stroke, which allows hydraulic fluid to be supplied from the hydraulic pump 90 to the left-turn port 40a of the swing motor 40.

[0073] The directional control valve section 51 is configured such that when pilot pressure is supplied to the right-swivel pilot port 51b, the directional control spool 51A is displaced from the neutral free position 51N to the right-swivel position 51R by a stroke corresponding to the magnitude of the pilot pressure. When the directional control spool 51A is in the right-swivel position 51R, the directional control valve section 51 forms an oil passage having an opening area corresponding to the stroke, which allows hydraulic fluid to be supplied from the hydraulic pump 90 to the right-swivel port 40b of the swivel motor 40.

[0074] The brake valve section 52 may be configured as a pilot-operated three-position switching valve. The brake valve section 52 has a brake spool 52A. As shown in Figure 3, the brake valve section 52 opens such that the opening area increases as the brake spool 52A moves away from the neutral brake position 52N.

[0075] The brake spool 52A is displaceable to a neutral brake position 52N that applies brake pressure to the swing motor 40, a left-turn release position 52L that releases the brake pressure, and a right-turn release position 52R that releases the brake pressure. The brake valve section 52 applies brake force to the swing motor 40 by narrowing the opening area of ​​the flow path (M / I opening area and M / O opening area) as the brake spool 52A approaches the neutral brake position 52N.

[0076] The brake valve section 52 has a left-turn pilot port 52a and a right-turn pilot port 52b. In the neutral brake mode, the left-turn pilot port 52a and the right-turn pilot port 52b are supplied with pilot pressure equivalent to the pilot pressure (secondary pressure of the actuator 70) supplied to the left-turn pilot port 51a and the right-turn pilot port 51b of the directional control valve section 51, respectively. On the other hand, in the neutral free mode, the secondary pressure of the actuator 70 is supplied as pilot pressure to the left-turn pilot port 51a and the right-turn pilot port 51b of the directional control valve section 51, while the brake spool operating pressure (secondary pressure of the brake spool control valve 62) output from the brake spool control valve 62 is supplied to a specific pilot port in the brake valve section 52 (in this embodiment, the left-turn pilot port 52a), as described later.

[0077] The brake spool 52A of the brake valve section 52 is held in the neutral brake position 52N when no pilot pressure is supplied to either the left-turn pilot port 52a or the right-turn pilot port 52b. When the brake spool 52A is in the neutral brake position 52N, the opening area of ​​the oil passage connecting the directional control valve section 51 and the left-turn port 40a of the slewing motor 40, and the opening area of ​​the oil passage connecting the directional control valve section 51 and the right-turn port 40b of the slewing motor 40 are narrowed to the minimum area. On the other hand, when pilot pressure is supplied to the left-turn pilot port 52a or the right-turn pilot port 52b, the brake spool 52A is displaced from the neutral brake position 52N toward the left-turn release position 52L or the right-turn release position 52R with a stroke corresponding to the magnitude of the pilot pressure, and as shown in Figure 3, the opening area of ​​the oil passage (M / I opening area and M / O opening area) increases to a degree corresponding to the stroke.

[0078] In this embodiment, the left-turn release position 52L is used as the specific release position 52X in the neutral free mode.

[0079] The directional control valve section 51 and the brake valve section 52 are arranged in series with respect to each other to constitute a so-called neutral brake type slewing control valve 50. Specifically, in the neutral brake mode, when pilot pressure is supplied to the left slewing pilot ports 51a, 52a or the right slewing pilot ports 51b, 52b, the slewing control valve 50 allows hydraulic fluid to be supplied to the left slewing port 40a or the right slewing port 40b of the slewing motor 40 at a flow rate corresponding to the pilot pressure. On the other hand, in the neutral brake mode, as the pilot pressure supplied to the pilot ports decreases, the state of the slewing control valve 50 approaches a neutral state, that is, a state in which the directional control spool 51A is in the neutral free position 51N and the brake spool 52A is in the neutral brake position 52N. As the state of the slewing control valve 50 approaches the neutral state, it applies a braking force to the slewing motor 40.

[0080] The oil passage between the brake valve section 52 and the left-turn port 40a of the swing motor 40 is connected to the tank via a relief valve 84, and the oil passage between the brake valve section 52 and the right-turn port 40b is connected to the tank via a relief valve 85. The relief valves 84 and 85 open when the pressure of the hydraulic fluid discharged from the swing motor 40 rises to the relief setting pressure as the directional switching spool 51A of the directional switching valve section 51 returns to the neutral free position 51N and the brake spool 52A of the brake valve section 52 returns to the neutral brake position 52N. As a result, the upper limit of the hydraulic fluid pressure is set to the relief setting pressure, i.e., the brake pressure.

[0081] Furthermore, the swivel control valve according to this disclosure only needs to exert a braking action when it returns to its neutral state, and its configuration is not necessarily limited to the configuration of the swivel control valve 50 shown in Figure 2. For example, pilot pressures of different magnitudes may be applied to the directional switching valve section 51 and the brake valve section 52 shown in Figure 2.

[0082] The brake spool control valve 62 is a valve for controlling the operation of the brake spool 52A in the neutral free mode. The brake spool control valve 62 is located in an oil passage connecting the pilot hydraulic power source 91 and a specific pilot port, which is either the left-turn pilot port 52a or the right-turn pilot port 52b. The brake spool control valve 62 may also be an electromagnetic pressure reducing valve capable of receiving a brake command (e.g., current value) in the turn stop control described later. In the specific example shown in Figure 2, the brake spool control valve 62 is located in an oil passage (brake spool oil passage 76) between the pilot hydraulic power source 91 and the left-turn pilot port 52a, and the specific pilot port is the left-turn pilot port 52a.

[0083] The mode switching valve 60 is an electromagnetic switching valve for switching the swivel mode in accordance with a mode switching command (e.g., current value) input from the controller 30. The mode switching valve 60 consists of, for example, an electromagnetic two-position switching valve. Specifically, the mode switching valve 60 switches between a position in which the brake spool oil passage 76 is opened while the swivel pressure reducing valve oil passage 75 is closed (neutral free mode position) and a position in which the swivel pressure reducing valve oil passage 75 is opened while the brake spool oil passage 76 is closed (neutral brake mode position) in accordance with the mode switching command. The swivel pressure reducing valve oil passage 75 is an oil passage connecting a specific swivel pressure reducing valve (in this embodiment, the left swivel pressure reducing valve 81), which is either the left swivel pressure reducing valve 81 or the right swivel pressure reducing valve 82, and the specific pilot port (in this embodiment, the left swivel pilot port 52a).

[0084] The pilot hydraulic power source 91 generates hydraulic pressure to supply pilot pressure to each of the multiple devices, such as the swivel control valve 50 and the actuator 70. The pilot hydraulic power source 91 is, for example, a pilot pump that is connected to the drive source and driven to discharge hydraulic fluid.

[0085] The operating device 70 comprises a swivel operation lever 71 and a swivel pilot valve 72 (remote control valve). The operating device 70 has the function of receiving a swivel command operation from an operator and allowing a pilot pressure corresponding to the swivel command operation to be supplied to the swivel control valve 50. The swivel command operation includes a left swivel command operation to operate the swivel motor 40 in the left swivel direction and a right swivel command operation to operate the swivel motor 40 in the right swivel direction. The swivel pilot valve 72 may have a left swivel proportional valve 72L that generates a secondary pressure corresponding to the left swivel command operation and a right swivel proportional valve 72R that generates a secondary pressure corresponding to the right swivel command operation.

[0086] The swivel operation lever 71 is a swivel operation member that receives the swivel command operation. The swivel operation lever 71 is connected to a swivel pilot valve 72 so as to be able to rotate around a predetermined axis when it receives the swivel command operation. The left swivel command operation is an operation to tilt the swivel operation lever 71 from its neutral position 70N, for example, to the left, and the right swivel command operation is an operation to tilt the swivel operation lever 71 from its neutral position 70N, for example, to the right. However, the swivel command operation according to this disclosure is not limited thereto. The swivel command operation may be, for example, an operation to slide the swivel operation member or an operation to press the swivel operation member.

[0087] The swivel pilot valve 72 is interposed between the pilot hydraulic power source 91 and each pilot port of the swivel control valve 50, and constitutes a pilot pressure control unit that controls the pilot pressure supplied from the pilot hydraulic power source 91 to the swivel control valve 50 to the operating pilot pressure corresponding to the swivel command operation supplied to the swivel operation lever 71.

[0088] Specifically, when a left turn command is given to the turn operation lever 71, the swivel pilot valve 72 opens to an opening degree corresponding to the magnitude of the left turn command. This allows the swivel pilot valve 72 to receive pilot pressure from the pilot hydraulic power source 91 to the left turn pilot port 51a of the directional control valve section 51 and the left turn pilot port 52a of the brake valve section 52. In other words, the pressure on the secondary side of the swivel pilot valve 72 (pilot valve secondary pressure) becomes the operating pilot pressure corresponding to the magnitude of the left turn command.

[0089] When a right turn command is issued to the turn operation lever 71, the swivel pilot valve 72 opens to an opening degree corresponding to the magnitude of the right turn command. This allows the swivel pilot valve 72 to receive pilot pressure from the pilot hydraulic power source 91 to the right turn pilot port 51b of the directional control valve section 51 and the right turn pilot port 52b of the brake valve section 52. In other words, the pressure on the secondary side of the swivel pilot valve 72 (pilot valve secondary pressure) becomes the operating pilot pressure corresponding to the magnitude of the right turn command.

[0090] The swivel stop control valve 80 reduces the operating pressure, which is the secondary pressure of the actuator 70, in response to a swivel stop command input from the controller 30. In this embodiment, the swivel stop control valve 80 includes a left swivel pressure reducing valve 81 and a right swivel pressure reducing valve 82. The left swivel pressure reducing valve 81 is interposed between the swivel pilot valve 72 and the left swivel pilot port 51a of the directional control valve section 51 and the left swivel pilot port 52a of the brake valve section 52, and has the function of limiting the upper limit of the pilot pressure supplied from the swivel pilot valve 72 to these left swivel pilot ports 51a and 52a. Similarly, the right swivel pressure reducing valve 82 is interposed between the swivel pilot valve 72 and the right swivel pilot port 51b of the directional control valve section 51 and the right swivel pilot port 52b of the brake valve section 52, and has the function of limiting the upper limit of the pilot pressure supplied from the swivel pilot valve 72 to these right swivel pilot ports 51b and 52b.

[0091] Specifically, the left-swivel pressure reducing valve 81 and the right-swivel pressure reducing valve 82 are each composed of electromagnetic pressure reducing valves capable of receiving a limit pilot pressure command signal (swivel stop command) from the controller 30 to specify the limit pilot pressure. The left-swivel pressure reducing valve 81 and the right-swivel pressure reducing valve 82 each allow the pilot valve secondary pressure (the pilot valve secondary pressure) generated on the secondary side when the swivel pilot valve 72 is opened to be input directly to the swivel control valve 50 if it is less than or equal to the limit pilot pressure corresponding to the limit pilot pressure command signal (swivel stop command). On the other hand, if the pilot valve secondary pressure exceeds the limit pilot pressure, the pilot pressure input to the swivel control valve 50 is limited to the limit pilot pressure.

[0092] The work machine 1 is equipped with multiple sensors. These multiple sensors include an operation detector, a swivel speed sensor 97, a swivel angle sensor 98, and an operator status detector 99.

[0093] The operation detector is a detector for detecting whether or not the operator 70 is receiving a rotation command operation. The operation detector may include, for example, pressure sensors 95 and 96. The pressure sensor 95 detects the left rotation pilot valve secondary pressure, which is the pressure generated on the secondary side of the rotation pilot valve 72 (the primary side of the left rotation pressure reducing valve 81) when the rotation operation lever 71 is given the left rotation command operation, and generates a left rotation pilot pressure detection signal, which is the corresponding electrical signal, and inputs it to the controller 30. Similarly, the pressure sensor 96 detects the right rotation pilot valve secondary pressure, which is the pressure generated on the secondary side of the rotation pilot valve 72 (the primary side of the right rotation pressure reducing valve 82) when the rotation operation lever 71 is given the right rotation command operation, and generates a right rotation pilot pressure detection signal, which is the corresponding electrical signal, and inputs it to the controller 30. As a result, the controller 30 can determine whether or not the operator 70 is receiving a rotation command operation.

[0094] The slewing speed sensor 97 detects the slewing speed of the upper slewing body 10 or the rotational speed of the slewing motor 40, generates a slewing speed detection signal, which is an electrical signal corresponding to the detection result, and inputs it to the controller 30.

[0095] The rotation angle sensor 98 detects the relative rotation angle of the upper rotation body 10 with respect to the lower body 11, generates a rotation angle detection signal which is an electrical signal corresponding to the rotation angle, and inputs it to the controller 30.

[0096] The operator status detector 99 has the function of determining the status of the operator inside the cab 12 of the work machine 1. The operator status detector 99 may be, for example, a dead man's switch system. Specifically, for example, the dead man's switch system may include a foot switch and a lever sensor, which is a sensor provided on the slewing operation lever 71. The foot switch may be, for example, located at the operator's feet and configured to detect whether or not the operator is stepping on the foot switch. The lever sensor may be configured to detect whether or not the slewing operation lever 71 is being held by the operator.

[0097] The deadman switch system, acting as an operator status detector 99, may input information regarding the operator's status as a predetermined signal to the controller 30 if it is not detected that the swivel lever 71 is being held by the operator, and / or that the foot switch is being pressed by the operator. Upon receiving this information (the predetermined signal), the controller 30 may control the operation of the alarm 101 to emit a warning sound, light, or the like. The controller 30 may also transmit this information to an external device 200.

[0098] The work machine 1 may include a parking control valve 86 and a parking brake 87. The parking brake 87 can brake the rotation of the upper slewing body 10 relative to the lower body 11 by applying braking force to the slewing motor 40. The parking control valve 86 may be a valve (e.g., an electromagnetic control valve) that can switch the parking brake 87 on and off in response to a parking command (e.g., current value) input from the controller 30.

[0099] The work machine 1 may be equipped with a display unit 94. The display unit 94 may be located, for example, inside the cab 12. The display unit 94 displays various information based on display commands from the controller 30. The display unit 94 may be, for example, a display (monitor).

[0100] The work machine 1 may be equipped with a communication device not shown in the figure, and may be configured to communicate with the external device 200 via the network 300. The work machine 1 and the external device 200 may be able to send and receive data from each other via the network 300.

[0101] The external device 200 may be an information terminal such as a tablet computer (so-called tablet), smartphone, laptop personal computer, or desktop personal computer. The external device 200 may be a remote control device for remotely operating the work machine 1 from a remote location away from the work machine 1. The external device 200 may also be a management device such as a server for managing the work performed by the work machine 1. The external device 200 may also be an information terminal for a supervisor to monitor the work performed by the work machine 1. In this case, video of the work performed by the work machine 1 may be acquired by an imaging device (not shown in the figure), and the acquired image data may be transmitted to the external device 200 via a network.

[0102] The controller 30 comprises a computer including a CPU, MPU, GPU, and other processing units, as well as memory. The controller 30 is electrically connected to a plurality of valves, such as a brake spool control valve 62, a swing stop control valve 80, and a parking switch valve 86, and to the plurality of sensors. The controller 30 controls the operation of each valve based on detection signals input from the plurality of sensors, swing mode information stored in memory, and information transmitted from the external device 200.

[0103] The controller 30 performs turning stop control. The controller 30 includes a mode setting unit 31, a turning stop control necessity determination unit 32, and a turning stop control unit 33 as functions related to this turning stop control. The mode setting unit 31 performs control to set the turning mode to either the neutral brake mode or the neutral free mode. The turning stop control necessity determination unit 32 determines whether turning stop control is necessary (for example, step S12 in Figure 5, described later). The turning stop control unit 33 performs turning stop control (for example, step S14 in Figure 5, and steps S21 and S22 in Figure 6, described later). Each of the mode setting unit 31, the turning stop control necessity determination unit 32, and the turning stop control unit 33 is realized by the arithmetic processing unit executing a program stored in the memory.

[0104] When the slewing control device 20 is in the neutral free mode, the controller 30 outputs a brake command to the brake spool control valve 62 so that the brake spool 52A moves from a specific release position 52X (in this embodiment, a release position for left slewing 52L) toward the neutral brake position 52N, regardless of the direction of rotation of the upper slewing body 10 (i.e., the direction of rotation of the slewing motor 40). This generates a braking force on the slewing motor 40, allowing the slewing motor 40 to be stopped.

[0105] As described above, the turning mode includes a neutral brake mode and a neutral free mode. Specifically, in the neutral brake mode, when the operator 70 receives the left turn command, the brake spool 52A moves from the neutral brake position 52N to the left turn release position 52L; when the operator 70 receives the right turn command, the brake spool 52A moves from the neutral brake position 52N to the right turn release position 52R; and when the operator 70 is returned to the neutral position 70N, the brake spool 52A moves to the neutral brake position 52N. In the neutral free mode, whether the operator 70 is not receiving the rotation command operation or is receiving the rotation command operation, the brake spool 52A is positioned at a specific release position 52X (in the specific example in Figure 2, the left rotation release position 52L). When the brake command output from the controller 30 is input to the brake spool control valve 62, the brake spool 52A moves from the specific release position 52X (left rotation release position 52L) toward the neutral brake position 52N. In the rotation control device 20 according to this embodiment, the controller 30 outputs the brake command when the rotation stop condition is met.

[0106] In this embodiment, the convenience of being able to switch between the two turning modes, the neutral brake mode and the neutral free mode, according to the work content is ensured, while suppressing the complexity of the system configuration of the work machine 1.

[0107] Figure 5 is a flowchart showing an example of the calculation process performed by the controller 30 of the rotation control device 20 according to this embodiment.

[0108] Operators and other personnel perform input operations to select a swivel mode on input devices such as the display unit 94 and the input unit 100. For example, when a worker performs an input operation to select the neutral free mode on the input device, the controller 30 sets the swivel mode to the neutral free mode. Specifically, the controller 30 controls the operation of the mode switching valve 60 so that the mode switching valve 60 is demagnetized. As a result, the mode switching valve 60 switches to the neutral free mode position. The controller 30 then inputs a command with a predetermined current value to the brake spool control valve 62 to adjust the secondary pressure (brake spool operating pressure) of the brake spool control valve 62. This brake spool operating pressure is input to the left swivel pilot port 52a of the swivel control valve 50, and the brake spool 52A moves to a specific release position 52X (left swivel release position 52L). At this time, the brake spool 52A moves to the maximum displacement position shown in Figure 3. The brake spool operating pressure may be greater than the operating pressure (secondary pressure of the actuator 70) input to the right-hand rotation pilot port 52b of the rotation control valve 50.

[0109] In the neutral free mode, the brake spool 52A is configured to be displaced in accordance with the brake spool operating pressure output from the brake spool control valve 62, while the directional switching spool 51A is configured to be displaced in accordance with the operating pressure output from the actuator 70. That is, when the actuator 70 receives a left turn command, a pilot pressure corresponding to the left turn command is supplied to the left turn pilot port 51a of the swivel control valve 50, and the directional switching spool 51A is displaced from the neutral free position 51N to the left turn position 51L with a stroke corresponding to the magnitude of the pilot pressure. Also, when the actuator 70 receives a right turn command, a pilot pressure corresponding to the right turn command is supplied to the right turn pilot port 51b of the swivel control valve 50, and the directional switching spool 51A is displaced from the neutral free position 51N to the right turn position 51R with a stroke corresponding to the magnitude of the pilot pressure.

[0110] When work by the work machine 1 is started at the work site, the controller 30 of the slewing control device 20 determines whether the slewing mode is in neutral free mode (step S11). The setting of the slewing mode is performed, as described above, based on input operations by the operator to equipment such as the display unit 94 and the input unit 100. The operator performs the input operation before or during work, and the controller 30 sets the slewing mode to the mode corresponding to the input operation and stores the setting in memory.

[0111] If the stored slewing mode (i.e., the slewing mode at that time) is not the neutral free mode (NO in step S11), the controller 30 determines whether the work by the work machine 1 has been completed (step S16). If the work has not been completed (NO in step S16), the process from step S11 onwards is repeated. For example, if the operator performs an input operation to a device such as the display 94 or input device 100 when the work is completed, the controller 30 can determine whether the work by the work machine 1 has been completed based on that input operation. If the work is completed (YES in step S16), the controller 30 terminates the slewing stop control and related controls.

[0112] If the turning mode is neutral free mode (YES in step S11), the controller 30 determines whether the turning stop condition has been met (step S12). If the turning stop condition has been met (YES in step S12), the controller 30 performs the process in step S13.

[0113] Specifically, for example, if the turning stop condition is that the controller 30 receives a predetermined signal from the operator status detector 99, then when the controller 30 receives the predetermined signal from the operator status detector 99 (YES in step S12), it performs the process in step S13.

[0114] Furthermore, if the turning stop condition is that the turning angle reaches a predetermined value, the controller 30 performs the process in step S13 when the turning angle input from the turning angle sensor 98 reaches the predetermined value (YES in step S12).

[0115] Furthermore, if the rotation stop condition is that a rotation stop signal is input from the external device 200 to the controller 30, the controller 30, upon receiving the rotation stop signal (YES in step S12), performs the process in step S13.

[0116] Next, the controller 30 determines whether the upper rotating body 10 is rotating or not (step S13). Specifically, the controller 30 can determine whether the upper rotating body 10 is rotating or not, that is, whether the rotating motor 40 is rotating or not, based on the rotation speed detection signal input to the controller from the rotation speed sensor 97.

[0117] If the upper rotating body 10 is not rotating, that is, if the upper rotating body 10 is stopped (NO in step S13), the controller 30 performs the process in step S16. If the upper rotating body 10 is not rotating (NO in step S13), the controller 30 may perform the same process as in step S15, that is, the process to apply the brakes (parking brake) to the rotation of the upper rotating body 10. If the upper rotating body 10 is rotating (YES in step S13), the controller 30 performs the rotation stop control in step S14. Note that in the control flow of Figure 5, the process in step S13 (determination of whether the upper rotating body 10 is rotating or not) may be omitted, and in this case, if the rotation stop condition is met in step S12 (YES in step S12), the controller 30 may perform the process in step S14 (rotation stop control).

[0118] Figure 6 is a flowchart showing an example of rotation stop control performed by the controller 30. In the following explanation, we will use as an example the case in which a right rotation command is given to the control unit 70 and the upper rotating body 10 is rotating to the right.

[0119] In the swing stop control, the controller 30 performs an operating pressure reduction process (step S21). Specifically, in step S21, the controller 30 inputs a swing stop command (limit pilot pressure command signal) to the left swing pressure reducing valve 81 and the right swing pressure reducing valve 82. As a result, the left swing pressure reducing valve 81 and the right swing pressure reducing valve 82 limit the operating pressure (pilot valve secondary pressure) of the swing pilot valve 72 to the limit pilot pressure. At this time, since the mode switching valve 60 is set to the neutral free mode position, when the operating pressure of the swing pilot valve 72 is limited to the limit pilot pressure, the direction switching spool 51A moves from the left swing position 51L or the right swing position 51R to the neutral free position 51N, while the position of the brake spool 52A is maintained at the specific release position 52X (left swing release position 52L). Therefore, the hydraulic fluid discharged from the swing motor 40 is allowed to circulate (circulate) between the swing motor 40 and the swing control valve 50, thereby causing the upper swing body 10 to swing by inertia.

[0120] Next, the controller 30 performs pilot pressure reduction processing (step S22). Specifically, in step S22, the controller 30 outputs a brake command to the brake spool control valve 62 so that the brake spool 52A moves from a specific release position 52X (left turn release position 52L) to a neutral brake position 52N.

[0121] Figure 4 is a graph showing an example of the time-dependent changes in the brake command, the outlet pressure of the swing motor 40, and the swing speed during swing-stop control by the controller 30. As shown in Figure 4, the brake command output by the controller 30 during the swing-stop control changes so that the brake spool 52A moves from a specific release position 52X to a neutral brake position 52N. In the specific example in Figure 4, the controller 30 outputs a brake command such that the current value input to the brake spool control valve 62 (the current value shown by the dashed line in Figure 4) gradually decreases over time. As a result, the brake spool 52A moves from the specific release position 52X to the neutral brake position 52N, and as shown in Figure 3, the area of ​​the meter-in opening (M / I opening area) and the area of ​​the meter-out opening (M / O opening area) gradually decrease. Consequently, as shown by the solid line in Figure 4, the outlet pressure of the swing motor 40 increases, and a relatively large brake pressure is generated at the outlet port of the swing motor 40. As a result, the rotation speed of the upper rotating body 10 (i.e., the rotation speed of the rotating motor 40) decreases, as shown by the solid line in Figure 4, and the rotation of the upper rotating body 10 (the rotation of the rotating motor 40) stops.

[0122] The above specific example is the case in which the rotation stop control is performed when a right rotation command is given to the control unit 70 and the upper rotating body 10 is rotating to the right (the first case). However, in the case in which the rotation stop control is performed when a left rotation command is given to the control unit 70 and the upper rotating body 10 is rotating to the left (the second case), the rotation of the upper rotating body 10 (the rotation of the rotation motor 40) can be stopped in the same manner as in the first case.

[0123] In the second case, when the brake command shown by the dashed line in Figure 4 is input to the brake spool control valve 62, the outlet pressure of the slewing motor 40 changes as shown by the dashed line, for example, and the slewing speed of the upper slewing body 10 (i.e., the rotational speed of the slewing motor 40) changes as shown by the dashed line, for example. The slight difference between the first and second cases is due to the characteristics of the M / I opening area and M / O opening area shown in Figure 3. That is, the slewing control valve 50 has the characteristic that the M / I opening area during leftward rotation is larger than the M / O opening area, except when the brake spool 52A is in the minimum displacement position and the maximum displacement position. Therefore, when the leftward rotation release position 52L is used as the specific release position 52X during rightward rotation, as in the first case, the area of ​​the meter-in opening of the slewing control valve 50 during rightward rotation is slightly smaller than the area of ​​the meter-in opening of the slewing control valve 50 during leftward rotation when comparing for the same stroke. Therefore, in the first case, when the left-turn release position 52L is used as the specific release position 52X during a right turn, the timing of the peak in the outlet pressure of the swing motor 40 is slightly delayed compared to the second case, and the timing of the stop of the swing is also slightly delayed. However, as shown in Figure 4, these timing delays are at a level that does not pose any particular practical problem.

[0124] As described above, in this embodiment, when the upper rotating body 10 rotates to the left, the meter-out side pressure of the rotating motor 40 is controlled by the area of ​​the meter-out opening for left rotation (M / O opening area) shown in Figure 3, and when the upper rotating body 10 rotates to the right, the meter-out side pressure of the rotating motor 40 is controlled by the area of ​​the meter-in opening for left rotation (M / I opening area) shown in Figure 3. This makes it possible to stop the upper rotating body 10 at a level of delay that does not pose any particular practical problems, while suppressing the complexity of the system configuration for stopping the upper rotating body 10 that is rotating in neutral free mode.

[0125] When the rotation stop control in step S14 of Figure 5 is completed, the controller 30 then controls the parking control valve 86 so that it is demagnetized (step S15). As a result, the parking brake 87 is turned on, and the brake is applied to the rotation of the upper rotating body 10. This prevents the upper rotating body 10 from rotating due to the slope of the ground, wind pressure, etc.

[0126] The following briefly describes other operations in the neutral free mode and operations in the neutral brake mode.

[0127] When the rotation mode is the neutral free mode, and the operating lever 71 of the operating device 70 is returned to the neutral position 70N while the upper rotating body 10 is rotating to the right after receiving a right rotation command from the operating device 70, the direction switching spool 51A returns to the neutral free position 51N, while the position of the brake spool 52A is maintained at the specific release position 52X (left rotation release position 52L). As a result, the hydraulic fluid is allowed to circulate between the rotation motor 40 and the rotation control valve 50. That is, the rotation motor 40 is allowed to rotate freely, and the upper rotating body 10 rotates by inertia. In this state, in order to stop the rotation of the upper rotating body 10, the operator may give the operating device 70 an operation opposite to the right rotation command, i.e., a left rotation command. This causes the pressure from the hydraulic pump 90 to act on the outlet port of the rotation motor 40, and the brake is applied.

[0128] Next, the case where the slewing mode is the neutral brake mode will be described. For example, when a worker performs an input operation to select the neutral brake mode on the input device, the controller 30 sets the slewing mode to the neutral brake mode. Specifically, the controller 30 controls the operation of the mode switching valve 60 so that the mode switching valve 60 is energized. As a result, the mode switching valve 60 switches to the neutral brake mode position. At this time, if the actuator 70 has not received a slewing command operation, the direction switching spool 51A is positioned in the neutral free position 51N, and the brake spool 52A is positioned in the neutral brake position 52N.

[0129] Then, when the actuator 70 receives a command to turn left, for example, the secondary pressure (operating pressure) of the actuator 70 is supplied to the left turn pilot port 51a and the left turn pilot port 52a of the swing control valve 50. As a result, the direction switching spool 51A moves from the neutral free position 51N to the left turn position 51L with a stroke corresponding to the magnitude of the pilot pressure, and the brake spool 52A moves from the neutral brake position 52N to the left turn release position 52L with a stroke corresponding to the magnitude of the pilot pressure. Consequently, hydraulic fluid is supplied to the left turn port of the swing motor 40, causing the upper swing body 10 to turn left.

[0130] Similarly, when the actuator 70 receives a command to turn right, for example, the secondary pressure (operating pressure) of the actuator 70 is supplied to the right-turn pilot port 51b and the right-turn pilot port 52b of the swivel control valve 50. As a result, the directional switching spool 51A moves from the neutral free position 51N to the right-turn position 51R with a stroke corresponding to the magnitude of the pilot pressure, and the brake spool 52A moves from the neutral brake position 52N to the right-turn release position 52R with a stroke corresponding to the magnitude of the pilot pressure. Consequently, hydraulic fluid is supplied to the right-turn port of the swivel motor 40, causing the upper swivel body 10 to turn right.

[0131] As the operating lever 71 of the control unit 70 moves toward the neutral position 70N, the direction switching spool 51A moves toward the neutral free position 51N, and the brake spool 52A moves toward the neutral brake position 52N. This slows down the rotation of the slewing motor 40, and the slewing speed of the upper slewing body 10 decreases. When the operating lever 71 of the control unit 70 moves toward the neutral position 70N, the direction switching spool 51A moves toward the neutral free position 51N, the brake spool 52A moves toward the neutral brake position 52N, and the rotation of the slewing motor 40 stops (the slewing of the upper slewing body 10 stops).

[0132] In the neutral brake mode, when the slewing motor 40 is rotating (when the upper slewing body 10 is slewing), if the slewing stop condition is met, the controller 30 controls the left slewing pressure reducing valve 81 and the right slewing pressure reducing valve 82 of the slewing stop control valve 80 so that the secondary pressure of the left slewing pressure reducing valve 81 and the secondary pressure of the right slewing pressure reducing valve 82 gradually decrease. As a result, the direction switching spool 51A moves toward the neutral free position 51N, and the brake spool 52A moves toward the neutral brake position 52N. As a result, the rotation of the slewing motor 40 gradually slows down, and the slewing speed of the upper slewing body 10 gradually decreases. When the secondary pressure of the left-swivel pressure reducing valve 81 and the secondary pressure of the right-swivel pressure reducing valve 82 fall to a predetermined value or less, the direction switching spool 51A moves to the neutral free position 51N, the brake spool 52A moves to the neutral brake position 52N, and the rotation of the swivel motor 40 stops (the swivel of the upper swivel body 10 stops).

[0133] [Differentiation] While embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and includes, for example, the following modifications.

[0134] (A) Variation 1 Figure 7 shows the main components of the slewing control device and the hydraulic circuit provided in the work machine according to a modified embodiment.

[0135] The modified hydraulic circuit shown in Figure 7 differs from the hydraulic circuit according to the embodiment shown in Figure 2 in that it includes a port relief pressure control valve 88, while the other components of the modified hydraulic circuit shown in Figure 7 are the same as those of the hydraulic circuit according to the embodiment shown in Figure 2.

[0136] The port relief pressure control valve 88 may be configured as an electromagnetic proportional valve, for example, as shown in Figure 7.

[0137] In this modified configuration, when the turning mode is the neutral brake mode, the set pressures (port relief pressures) of the relief valves 84 and 85, which are adjusted by the port relief pressure control valve 88, are set to be higher than when the turning mode is the neutral free mode. That is, in the neutral brake mode, the port relief pressure is set to a relatively high pressure, and in the neutral free mode, the port relief pressure is set to a relatively low pressure.

[0138] In this modified example, in the neutral free mode, if the rotation stop condition is met (YES in step S12 of Figure 5) and the upper rotating body 10 is rotating (YES in step S13 of Figure 5), the controller 30 performs rotation stop control (step S14).

[0139] In this swing stop control, the controller 30 performs an operating pressure reduction process (step S21 in Figure 6). Specifically, in step S21, the controller 30 inputs a swing stop command (limit pilot pressure command signal) to the left swing pressure reducing valve 81 and the right swing pressure reducing valve 82. As a result, the left swing pressure reducing valve 81 and the right swing pressure reducing valve 82 limit the operating pressure (pilot valve secondary pressure) of the swing pilot valve 72 to the limit pilot pressure. At this time, since the mode switching valve 60 is set to the neutral free mode position, when the operating pressure of the swing pilot valve 72 is limited to the limit pilot pressure, the direction switching spool 51A moves from the left swing position 51L or the right swing position 51R to the neutral free position 51N, while the position of the brake spool 52A is maintained at the specific release position 52X (left swing release position 52L). Therefore, the hydraulic fluid discharged from the swing motor 40 is allowed to circulate (circulate) between the swing motor 40 and the swing control valve 50, thereby causing the upper swing body 10 to swing by inertia.

[0140] In this modified example, after step S21, the controller 30 controls the port relief pressure by gradually changing the command pilot pressure of the port relief pressure control valve 88 (solenoid proportional valve), thereby slowly increasing the port relief pressure. This reduces the amount of hydraulic fluid that was being relieved from the relief valves 84 and 85 to the tank circuit and forms a circulation circuit that returns it to the swivel control valve 50 (direction switching spool 51A and brake spool 52A).

[0141] Next, the controller 30 performs pilot pressure reduction processing (step S22). Specifically, in step S22, the controller 30 outputs a brake command to the brake spool control valve 62 so that the brake spool 52A moves from a specific release position 52X (left turn release position 52L) to a neutral brake position 52N.

[0142] In this modified example, once the rotation stop control in step S14 of Figure 5 is completed, the controller 30 controls the parking control valve 86 so that it is demagnetized (step S15). As a result, the parking brake 87 is turned on, and the brake is applied to the rotation of the upper rotating body 10. This prevents the upper rotating body 10 from rotating due to the slope of the ground, wind pressure, etc.

[0143] (B) Variation 2 In the above embodiment, the lower body 11 is configured to be self-propelled, but the lower body in this disclosure may be composed of a base that is not self-propelled, in which case the upper rotating body 10 may be rotatably supported on the base which serves as the lower body.

[0144] (C) Variation 3 In the above embodiment, the left turn release position 52L is used as the specific release position 52X in the neutral free mode, but the right turn release position 52R may also be used as the specific release position 52X.

[0145] (D) Modification 4 The dead man's switch system may be configured as follows, for example. The lever sensor described above may be a touch sensor, or a sensor that senses the force with which the operator grips the slewing lever 71. The dead man's switch system may also include a switch that is pressed when the operator is in a normal operating state. This switch may be, for example, a foot switch, or a switch located where the operator's hand and / or elbow rests. The dead man's switch system may also include sensors that detect the load acting on the seat, such as the seat cushion and backrest, and / or the temperature of the seat. The dead man's switch system may also include an imaging device such as a camera that detects the operator's state. In this case, the dead man's switch system may use methods such as image analysis (image diagnosis) and image recognition of image data obtained by the imaging device to make various determinations as determinations of the operator's state, such as determining the operator's posture, determining whether the slewing lever 71 is being gripped, and determining whether a pedal such as a foot switch is being pressed. Artificial intelligence (AI) may be used for these determinations. [Explanation of symbols]

[0146] 1: Working Machinery 10: Upper rotating body 20: Swing control device 30: Controller 40: Swivel motor 50: Swivel control valve 51A: Directional switching spool 51L: Left turning position 51N: Neutral free position 51R: Right turn position 52A: Brake spool 52L: Release position for left turn 52N: Neutral brake position 52R:Release position for right turn 52X: Release position 60: Mode switching valve 62: Brake spool control valve 70:Operator 80: Swivel stop control valve 90: Hydraulic pump 200: External device

Claims

1. A slewing control device for controlling a work machine, The aforementioned work machine is A hydraulic pump that discharges hydraulic fluid, A swing motor that operates upon the supply of the aforementioned hydraulic fluid, A mode switching valve that switches between neutral brake mode and neutral free mode, A swivel control valve having a direction-switching spool and a brake spool, The system includes a brake spool control valve that controls the operation of the brake spool, The direction-switching spool is displaceable between a neutral free position, a left-turn position, and a right-turn position, forming a flow path for circulating the hydraulic fluid between the swivel motor and the swivel control valve. The brake spool is displaceable between a neutral brake position that applies brake pressure to the swing motor and a release position that releases the brake pressure. The slewing control device comprises a controller configured to output a brake command to the brake spool control valve so that, in the neutral free mode, the brake spool moves from the release position to the neutral brake position, regardless of the slewing direction of the upper slewing body of the work machine.

2. The swing control device according to claim 1, wherein the controller is configured to output the brake command when a preset swing stop condition is met in order to determine whether or not it is necessary to stop the swing of the upper swing body.

3. The aforementioned hydraulic pump, The aforementioned swing motor and, The mode switching valve and, The aforementioned swivel control valve, The aforementioned brake spool control valve, A work machine comprising the rotation control device described in claim 1.

4. The work machine according to claim 3, wherein the brake spool is displaceable to a neutral brake position, a left turn release position, and a right turn release position, and in the neutral free mode, regardless of the turning direction of the upper rotating body, either the left turn release position or the right turn release position is used as the release position.

5. It is further equipped with an operating device that receives left turn command operations and right turn command operations, The actuator is configured to output operating pressures corresponding to the left turn command operation and the right turn command operation, respectively. In the neutral brake mode, the directional switching spool and the brake spool are configured to be displaced in accordance with the operating pressure. In the neutral free mode, the direction switching spool is configured to be displaced in accordance with the operating pressure, while the brake spool is configured to be displaced in accordance with the brake spool operating pressure output from the brake spool control valve, as described in claim 3 or 4.

6. The system further includes a swing stop control valve that reduces the operating pressure in response to a swing stop command input from the controller, The work machine according to claim 5, wherein in the neutral free mode, the controller is configured to, when a pre-set rotation stop condition is met for determining whether or not it is necessary to stop the rotation of the upper rotating body, input the rotation stop command to the rotation stop control valve to displace the direction switching spool to the neutral free position, and input the brake command to the brake spool control valve to displace the brake spool from the release position to the neutral brake position.

7. The working machine according to claim 3 or 4, wherein the area of ​​the meter-in opening and the area of ​​the meter-out opening are the same when the brake spool is positioned in the release position.

8. A turning control method using the turning control device described in claim 1, A slewing control method comprising the controller of the slewing control device outputting the brake command to the brake spool control valve such that, in the neutral free mode, the brake spool moves from the release position to the neutral brake position, regardless of the slewing direction of the upper slewing body.

Images