Swivel control device and swivel work machine equipped therewith

Abstract

To provide a revolution control device capable of suppressing a decrease in deceleration torque during deceleration of a revolution motor, and to provide a revolution-type work machine comprising the same.SOLUTION: A revolution control device 101 comprises: a hydraulic pump 21 discharging hydraulic oil; a revolution motor 11 operating by being supplied with the hydraulic oil; a revolution control valve 31 interposed between the hydraulic pump 21 and the revolution motor 11; a revolution operation device 41 receiving a revolution operation by an operator; and a controller 70 performing deceleration control adjusting deceleration torque to decelerate the revolution motor 11. The revolution control valve 31 has a valve body 31B capable of operating in a range including a first operating range that opens a meter-out passage and closes a meter-in passage and a second operating range that opens the meter-out passage and the meter-in passage. The controller 70 performs deceleration control while maintaining a state in which the valve body 31B is disposed within the first operating range.SELECTED DRAWING: Figure 3

Description

【Technical Field】 【0001】 The present disclosure relates to a swing control device for a swing-type working machine such as a hydraulic excavator. 【Background Art】 【0002】 Patent Document 1 discloses a hydraulic excavator as a swing-type working machine. This hydraulic excavator generally includes a lower traveling body, an upper swing body rotatably supported by the lower traveling body, a working device supported by the upper swing body and including a boom and an arm, a hydraulic pump that discharges hydraulic oil, a swing motor that is a hydraulic motor for swinging the upper swing body, a boom cylinder that is a hydraulic cylinder for raising and lowering the boom, and an arm cylinder that is a hydraulic cylinder for rotating the arm. Further, Patent Document 2 discloses a crane as a swing-type working machine. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2019-27261 【Patent Document 2】 Japanese Patent Application Laid-Open No. 2019-2558 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 In the swing-type working machine as described above, when the swing motor decelerates, for some reason, the meter-in pressure of the swing motor increases, the deceleration torque decreases, and the braking effect may deteriorate. Specific examples of cases where such problems occur are as follows. 【0005】 For example, in a hydraulic excavator, the hydraulic fluid discharged by the hydraulic pump is used not only to operate the slewing motor but also to operate other hydraulic actuators (e.g., boom cylinders). In this case, the hydraulic pump is used for both supplying hydraulic fluid to the slewing motor and to the other hydraulic actuators. In such cases, during a combined operation in which the slewing operation to move the slewing motor and the operation to move the other hydraulic actuators are performed simultaneously, the meter-in pressure of the slewing motor may rise due to the influence of the operating pressure of the other hydraulic actuators. Hereafter, this will be referred to as hydraulic interference. If this hydraulic interference occurs during deceleration of the slewing motor, the differential pressure in the slewing motor may decrease, resulting in a reduction in deceleration torque and a decrease in braking effectiveness. 【0006】 Furthermore, even during single-unit slewing operations, rather than combined operations, if the amount of hydraulic fluid discharged from the hydraulic pump exceeds the flow rate of hydraulic fluid that should flow into the slewing motor during deceleration, the meter-in pressure of the slewing motor may become excessively high due to the influence of the discharge pressure of the hydraulic pump. In this case as well, the differential pressure in the slewing motor decreases, which can reduce the deceleration torque and decrease the effectiveness of the brakes. 【0007】 The purpose of this disclosure is to provide a slewing control device that can suppress the decrease in deceleration torque when a slewing motor is decelerated, and a slewing work machine equipped with the same. [Means for solving the problem] 【0008】 Provided is a slewing control device for a slewing work machine comprising a machine body, an upper slewing body rotatably supported on the machine body, and a work device supported on the upper slewing body, comprising: a hydraulic pump for discharging hydraulic fluid; a slewing motor that operates when the hydraulic fluid is supplied; a slewing control valve interposed between the hydraulic pump and the slewing motor; a slewing actuator for receiving slewing operations by an operator; and a controller for performing deceleration control to adjust the deceleration torque for decelerating the slewing motor, wherein the slewing control valve has a valve body that can operate within a range including a first operating range that opens the meter-out passage and closes the meter-in passage, and a second operating range that opens both the meter-out passage and the meter-in passage, and the controller performs the deceleration control while maintaining the state in which the valve body is positioned within the first operating range. 【0009】 In this swing control device, the controller performs deceleration control with the meter-in passage of the swing control valve closed. Therefore, when the swing motor is decelerated, the differential pressure of the swing motor is not affected by fluctuating factors such as hydraulic interference and the discharge rate of hydraulic fluid from the hydraulic pump, as described above. Consequently, when the swing motor is decelerated, it is possible to suppress an excessive rise in the meter-in pressure of the swing motor due to the aforementioned fluctuating factors. This suppresses the decrease in the differential pressure of the swing motor (meter-out pressure - meter-in pressure) due to the aforementioned fluctuating factors. As a result, the decrease in deceleration torque can be suppressed, and the decrease in braking effectiveness can be suppressed. 【0010】 Preferably, the controller determines a target turning speed according to the amount of the turning operation, and performs the deceleration control when the actual turning speed is greater than the target turning speed. In this configuration, the controller can appropriately determine whether or not to perform deceleration control based on the result of comparing the target turning speed, which is determined according to the amount of the turning operation by the operator, with the actual turning speed. 【0011】 In the deceleration control, it is preferable that the controller controls the opening size of the meter-out passage of the swing control valve so that the deceleration torque is proportional to the amount of the swing operation. In this configuration, in the deceleration control, it is possible to generate a deceleration torque proportional to the amount of the swing operation performed by the operator while suppressing the decrease in the differential pressure of the swing motor caused by the fluctuating factors. 【0012】 Preferably, the controller stores in advance a reference moment of inertia, which is the moment of inertia around the pivot axis in the reference posture of the rotating body including the upper slewing body and the working device, calculates the actual moment of inertia, which is the moment of inertia around the pivot axis in the actual posture of the rotating body, and adjusts the deceleration torque using the comparison result between the actual moment of inertia and the reference moment of inertia. In this configuration, the controller adjusts the deceleration torque taking into account the actual moment of inertia which changes according to the change in posture of the working device, so that the slewing motor can be decelerated at a desired acceleration corresponding to the amount of slewing operation, regardless of the posture of the working device. 【0013】 The provided slewing work machine comprises the slewing control device described above, the machine body, the upper slewing body, and the work device. This slewing work machine can suppress the decrease in differential pressure of the slewing motor caused by the fluctuating factors, and therefore can suppress the decrease in deceleration torque when the slewing motor is decelerated. [Effects of the Invention] 【0014】 According to this disclosure, a slewing control device that can suppress the decrease in deceleration torque when a slewing motor is decelerated, and a slewing work machine equipped therewith are provided. [Brief explanation of the drawing] 【0015】 [Figure 1] This is a side view showing a slewing work machine equipped with a slewing control device according to an embodiment of the present disclosure. [Figure 2] This is a diagram showing the aforementioned turning control device. [Figure 3]It is a graph showing the characteristics of the turning control valve of the turning control device. [Figure 4] It is a diagram for explaining two cases regarding the lever operation during turning deceleration. [Figure 5] It is a diagram showing an example of a map used for deceleration control by the controller of the turning control device. [Figure 6] It is a diagram showing an example of a map used for acceleration constant speed control by the controller. [Figure 7] It is a flowchart showing an example of the arithmetic processing performed by the controller. [Figure 8] It is a map showing the relationship between the lever operation amount of the turning operation given to the turning operation device of the turning control device and the target turning speed (or target turning flow rate). [Figure 9] It is a flowchart showing an example of the arithmetic processing performed by the controller. [Figure 10] It is a flowchart showing an example of the arithmetic processing performed by the controller. [Figure 11] It is a flowchart showing an example of the arithmetic processing performed by the controller. [Figure 12] It is a flowchart showing an example of the arithmetic processing performed by the controller. [Figure 13] It is a map showing the relationship between the target turning flow rate (or target turning speed) and the valve opening degree of the turning control valve. [Figure 14] It is a map showing the relationship between the pump flow rate and the pump command current value. [Figure 15] It is a flowchart showing an example of the arithmetic processing performed by the controller. [Figure 16] It is a map showing the relationship between the lever operation amount and the target turning acceleration. [Figure 17] It is a flowchart showing an example of the arithmetic processing performed by the controller. 【Embodiments for Carrying Out the Invention】 【0016】 Embodiments of this disclosure will be described with reference to the drawings. 【0017】 The slewing work machine 100 shown in Figure 1 is a hydraulic excavator. As shown in Figures 1 and 2, this slewing work machine 100 comprises a lower traveling body 1, an upper slewing body 2, a work device 3, multiple hydraulic pumps, multiple hydraulic actuators, multiple control valves, multiple operating devices, multiple pilot pressure regulating valves, multiple detectors, and a controller 70. 【0018】 The lower running body 1 comprises a pair of left and right crawler running devices and a lower frame supported by these crawler running devices. The upper slewing body 2 is supported by the lower running body 1 so as to be rotatable around a slewing axis Z. The slewing axis Z is an axis extending in the vertical direction. The upper slewing body 2 comprises an upper frame supported by the lower frame and a cab supported at the front of the upper frame. The lower running body 1 is an example of a machine body. 【0019】 The working device 3 includes a boom 4 supported by an upper slewing body 2 so as to be able to raise and lower, an arm 5 rotatably supported by the boom 4, and a tip attachment rotatably supported by the arm 5. In this embodiment, the tip attachment is a bucket 6. The boom 4 has a boom base end rotatably attached to the upper slewing body 2 and a boom tip end on the opposite side. The arm 5 has an arm base end rotatably attached to the boom tip and an arm tip end on the opposite side. The bucket 6 has a base end rotatably attached to the arm tip. 【0020】 Each of the multiple hydraulic pumps discharges hydraulic fluid when driven by a power source such as an engine (not shown). As shown in Figures 1 and 2, the multiple hydraulic pumps include a first pump 21 and a pilot pump 24. The first pump 21 supplies hydraulic fluid to at least one of the multiple hydraulic actuators. The pilot pump 24 supplies pilot pressure to each of the multiple control valves. The multiple hydraulic pumps may further include a second pump (not shown) that supplies hydraulic fluid to at least one of the multiple hydraulic actuators. 【0021】 The first pump 21 is a variable displacement hydraulic pump capable of changing its capacity in response to a pump capacity command from the controller 70. Specifically, the first pump 21 is equipped with a regulator (not shown in the diagram) for capacity control, and when a pump capacity command from the controller 70 is input to the regulator, the tilt angle of the first pump 21 changes in accordance with the pump capacity command. This changes the capacity (displacement volume) of the first pump 21, and consequently changes the discharge amount of hydraulic fluid discharged from the first pump 21. 【0022】 Each of the multiple hydraulic actuators is operated by the supply of hydraulic fluid from at least one of the first pump 21 and the second pump. As shown in Figures 1 and 2, the multiple hydraulic actuators include a slewing motor 11 for slewing the upper slewing body 2, a boom cylinder 7 for raising and lowering the boom 4, an arm cylinder 8 for rotating the arm 5, and a bucket cylinder 9 for rotating the bucket 6. In Figure 2, the arm cylinder 8 and bucket cylinder 9 are not shown. 【0023】 The slewing motor 11 is a hydraulic motor that operates by receiving hydraulic fluid supplied from the first pump 21. The slewing motor 11 has a pair of ports. The pair of ports includes a right-slewing port to which hydraulic fluid is supplied when the upper slewing body 2 is slewing to the right, and a left-slewing port to which hydraulic fluid is supplied when the upper slewing body 2 is slewing to the left. The boom cylinder 7 is a hydraulic cylinder that operates by receiving hydraulic fluid supplied from the first pump 21. The arm cylinder 8 and the bucket cylinder 9 are each hydraulic cylinders that operate by receiving hydraulic fluid supplied from either the first pump 21 or the second pump. 【0024】 In the specific example shown in Figure 2, the slewing motor 11 and the boom cylinder 7 are connected in parallel to the first pump 21. The first pump 21 is used to supply hydraulic fluid to both the slewing motor 11 and the boom cylinder 7. The hydraulic fluid discharged by the first pump 21 is used not only to operate the slewing motor 11 but also to operate the boom cylinder 7. However, the targets of the hydraulic fluid supply from the first pump 21 are not limited to the specific example in Figure 2. For example, the first pump 21 may be used to supply hydraulic fluid to both the slewing motor 11 and the arm cylinder 8, or it may be used to supply hydraulic fluid to both the slewing motor 11 and the bucket cylinder 9. 【0025】 The control valves include a swing control valve 31, a boom control valve 32, an arm control valve, and a bucket control valve. In Figure 2, the arm control valve and bucket control valve are not shown. 【0026】 Each of the control valves has a spool that adjusts the opening size of the meter-in passage and the meter-out passage, and a pair of pilot ports that receive pilot pressure from the pilot pump 24. The spool is an example of a valve body. In each of the control valves, when either of the pair of pilot ports receives pilot pressure, the spool is displaced from its neutral position in the direction corresponding to the pilot port that received the pilot pressure by an amount of displacement corresponding to the magnitude of the pilot pressure. This adjusts the opening size (opening area) of the meter-in passage and the meter-out passage. 【0027】 The swivel control valve 31 is interposed between the first pump 21 and the swivel motor 11 and opens and closes to adjust the direction and flow rate of the hydraulic fluid supplied from the first pump 21 to the swivel motor 11. The first pump 21 and the swivel control valve 31 are connected by a supply line 92, and the swivel control valve 31 and the tank 99 are connected by a return line 93. 【0028】 The swivel control valve 31 has a pair of pilot ports, including a right-swivel pilot port and a left-swivel pilot port. The swivel control valve 31 and the right-swivel port of the swivel motor 11 are connected by a right-swivel conduit 85. The swivel control valve 31 and the left-swivel port of the swivel motor 11 are connected by a left-swivel conduit 86. 【0029】 The swivel control valve 31 comprises a case 31A and a spool 31B disposed within the case 31A. The spool 31B is displaced within the case 31A relative to the case 31A in response to the pilot pressure supplied to either the right-swivel pilot port or the left-swivel pilot port. The spool 31B of the swivel control valve 31 is configured to operate within an operating range that includes a first operating range (deceleration region) and a second operating range (constant-velocity acceleration region). The first operating range is the range in which the swivel control valve 31 opens the meter-out passage and closes the meter-in passage. The second operating range is the range in which the swivel control valve 31 opens both the meter-out passage and the meter-in passage. The first operating range is used when decelerating the swivel motor 11, and the second operating range is used when accelerating the rotation of the swivel motor 11 and when rotating the swivel motor 11 at a constant speed. 【0030】 When the spool 31B is positioned within the second operating range, that is, when the meter-in passage is open and the meter-out passage is open, the swivel control valve 31 allows hydraulic fluid from the first pump 21 to be supplied to the swivel motor 11 and allows hydraulic fluid discharged from the swivel motor 11 to return to the tank 99. When the spool 31B is positioned within the first operating range, that is, when the meter-out passage is open and the meter-in passage is closed, the swivel control valve 31 allows hydraulic fluid discharged from the swivel motor 11 to return to the tank 99, but prevents hydraulic fluid from the first pump 21 from being supplied to the swivel motor 11. 【0031】 Figure 3 is a graph showing the characteristics of the swivel control valve 31. Figure 3 shows the relationship between pilot pressure and valve opening. Pilot pressure is the pressure supplied to the pilot port (right-swivel pilot port or left-swivel pilot port) of the swivel control valve 31. In both cases, whether the pilot pressure is supplied to the right-swivel pilot port or the left-swivel pilot port, the swivel control valve 31 operates with the characteristics shown in Figure 3. 【0032】 In the swivel control valve 31, the displacement of the spool 31B from the neutral position increases as the pilot pressure supplied to the pilot port increases. Therefore, the horizontal axis in Figure 3 represents the magnitude of the pilot pressure supplied to the pilot port, and indirectly represents the displacement of the spool 31B from the neutral position. 【0033】 As shown in Figure 3, if no pilot pressure is supplied to the pilot port, or if a pilot pressure of less than or equal to the first pressure P1 is supplied to the pilot port, the spool 31B is positioned in the neutral position or near the neutral position. In this case, the valve opening, i.e., the opening size of the meter-in passage (opening of the M / I opening) and the opening size of the meter-out passage (opening of the M / O opening), are both zero. 【0034】 When the pilot pressure supplied to the pilot port is greater than the first pressure P1 and less than or equal to the second pressure P2, the spool 31B is positioned within the first operating range. In this case, the meter-out passage is open while the meter-in passage is closed. The opening size of the meter-out passage gradually increases as the pilot pressure increases from the first pressure P1 to the second pressure. 【0035】 When the pilot pressure supplied to the pilot port is greater than the second pressure P2, the spool 31B is positioned within the second operating range, with both the meter-out passage and the meter-in passage open. The opening size of the meter-out passage and the opening size of the meter-in passage each increase progressively as the pilot pressure increases from the second pressure P2. The opening size of the meter-out passage increases progressively as the pilot pressure increases from the first pressure P1 to the third pressure P3. The third pressure P3 is greater than the second pressure P2. The opening size of the meter-in passage increases progressively as the pilot pressure increases from the second pressure P2 to the third pressure P3. 【0036】 The boom control valve 32 is interposed between the first pump 21 and the boom cylinder 7 and opens and closes to adjust the direction and flow rate of the hydraulic fluid supplied from the first pump 21 to the boom cylinder 7. The arm control valve is interposed between either the first pump 21 or the second pump and the arm cylinder 8 and opens and closes to adjust the direction and flow rate of the hydraulic fluid supplied from the pump to the arm cylinder 8. The bucket control valve is interposed between either the first pump 21 or the second pump and the bucket cylinder 9 and opens and closes to adjust the direction and flow rate of the hydraulic fluid supplied from the pump to the bucket cylinder 9. 【0037】 The multiple controls include a slewing control 41, a boom control, an arm control, and a bucket control. In Figure 2, the boom control, arm control, and bucket control are not shown. 【0038】 The slewing control unit 41 comprises a slewing control lever 41A and an output unit 41B. The slewing control lever 41A of the slewing control unit 41 can receive a rightward slewing operation by the operator to cause the upper slewing body 2 to perform a rightward slewing movement, and a leftward slewing operation by the operator to cause the upper slewing body 2 to perform a leftward slewing movement. When a rightward slewing operation is applied to the slewing control lever 41A by the operator, the output unit 41B of the slewing control unit 41 outputs a slewing control signal (rightward slewing operation signal) to the controller 70 corresponding to the amount of lever operation for the rightward slewing operation. When a leftward slewing operation is applied to the slewing control lever 41A by the operator, the output unit 41B of the slewing control unit 41 outputs a slewing control signal (leftward slewing operation signal) corresponding to the amount of lever operation for the leftward slewing operation. 【0039】 Similarly, the boom operator includes an operating lever to which the operator provides boom operation for operating the boom cylinder 7, and an output device that outputs a boom operation signal to the controller 70, which is a signal corresponding to the direction and amount of operation applied to the operating lever. The arm operator includes an operating lever to which the operator provides arm operation for operating the arm cylinder 8, and an output device that outputs an arm operation signal to the controller 70, which is a signal corresponding to the direction and amount of operation applied to the operating lever. The bucket operator includes an operating lever to which the operator provides bucket operation for operating the bucket cylinder 9, and an output device that outputs a bucket operation signal to the controller 70, which is a signal corresponding to the direction and amount of operation applied to the operating lever. The operation signals output from each of the outputs of these operators are input to the controller 70. Note that one operating lever may be used for both operators. 【0040】 Each of the multiple pilot pressure regulating valves is interposed between the pilot pump 24 and the pilot port of one of the control valves. Each of the multiple pilot pressure regulating valves outputs a secondary pressure obtained by reducing the pressure oil of the pilot pump 24 in response to a control command input from the controller 70, and this secondary pressure is supplied to the pilot port of the control valve corresponding to the pilot pressure regulating valve. In this embodiment, each of the multiple pilot pressure regulating valves is composed of a proportional valve, such as an electromagnetic proportional valve. Specifically, the multiple pilot pressure regulating valves include a pair of slewing proportional valves 51, 51 (a pair of slewing pilot pressure regulating valves 51, 51), a pair of boom proportional valves, a pair of arm proportional valves, and a pair of bucket proportional valves. In Figure 2, the pair of boom proportional valves, the pair of arm proportional valves, and the pair of bucket proportional valves are not shown. 【0041】 The pair of swivel proportional valves 51, 51 includes a right-swivel proportional valve 51 interposed between the pilot pump 24 and the right-swivel pilot port of the swivel control valve 31, and a left-swivel proportional valve 51 interposed between the pilot pump 24 and the left-swivel pilot port of the swivel control valve 31. 【0042】 When the swivel control lever 41A of the swivel control device 41 receives a right swivel operation, the output device 41B of the swivel control device 41 inputs a right swivel operation signal to the controller 70, and the controller 70 inputs a right swivel control command to the right swivel proportional valve 51. The right swivel proportional valve 51 generates a pilot pressure, which is a secondary pressure corresponding to the right swivel control command, and the generated pilot pressure is supplied to the right swivel pilot port of the swivel control valve 31. The spool 31B of the swivel control valve 31 is displaced from the neutral position in the direction corresponding to the right swivel operation by an amount of displacement corresponding to the supplied pilot pressure. As a result, the valve opening of the swivel control valve 31, that is, the opening size of the meter-in passage and the opening size of the meter-out passage of the swivel control valve 31, are adjusted to an amount corresponding to the displacement of the spool 31B according to the characteristics shown in Figure 3. 【0043】 Similarly, when the slewing lever 41A of the slewing control unit 41 receives a left slewing operation, the output unit 41B of the slewing control unit 41 inputs a left slewing operation signal to the controller 70, and the controller 70 inputs a left slewing control command to the left slewing proportional valve 51. The left slewing proportional valve 51 generates a pilot pressure, which is a secondary pressure corresponding to the left slewing control command, and the generated pilot pressure is supplied to the left slewing pilot port of the slewing control valve 31. The spool 31B of the slewing control valve 31 is displaced from the neutral position in the direction corresponding to the left slewing operation by an amount of displacement corresponding to the supplied pilot pressure. As a result, the valve opening of the slewing control valve 31, that is, the opening size of the meter-in passage and the opening size of the meter-out passage of the slewing control valve 31, are adjusted to an amount corresponding to the displacement of the spool 31B according to the characteristics shown in Figure 3. 【0044】 A pair of boom proportional valves includes a boom-raising proportional valve interposed between the pilot pump 24 and the boom-raising pilot port of the boom control valve, and a boom-down proportional valve interposed between the pilot pump 24 and the boom-down pilot port of the boom control valve. 【0045】 When the operating lever of the boom operator receives a boom raising or boom lowering operation, the output of the boom operator inputs an operation signal corresponding to the operation to the controller 70, and the controller 70 inputs a control command to the proportional valve of the boom raising proportional valve and boom lowering proportional valve that corresponds to the operation. The proportional valve generates a pilot pressure, which is a secondary pressure corresponding to the control command, and the generated pilot pressure is supplied to the pilot port of the boom control valve 32 that corresponds to the operation. The spool of the boom control valve 32 is displaced from the neutral position in the direction corresponding to the operation by an amount of displacement corresponding to the supplied pilot pressure. As a result, the opening degree of the boom control valve 32, that is, the opening size of the meter-in passage and the opening size of the meter-out passage of the boom control valve 32, are adjusted to a size corresponding to the amount of spool displacement. As a result, the hydraulic fluid discharged from the first pump 21 is supplied to the boom cylinder 7, the boom cylinder 7 is operated and the boom 4 moves up and down. 【0046】 The operation of the pair of arm proportional valves and the resulting rotation of arm 5 are the same as the operation of the pair of boom proportional valves and the resulting luffing motion of boom 4 described above, and the operation of the pair of bucket proportional valves and the resulting rotation of bucket 6 are the same as the operation of the pair of boom proportional valves and the resulting luffing motion of boom 4 described above. Therefore, a detailed explanation of these is omitted. 【0047】 The multiple detectors include a slewing speed detector 62, a differential pressure detector 65, a boom holding pressure detector 66, and an attitude detector 67. Each of the multiple detectors inputs a detection signal corresponding to the detection result it has detected to the controller 70. 【0048】 The slewing speed detector 62 detects the operating speed (e.g., angular velocity) of the slewing motor 11 or a speed correlated thereto (e.g., the slewing speed of the upper slewing body 2). The differential pressure detector 65 detects the differential pressure in the slewing motor 11. Specifically, the differential pressure detector 65 includes a first pressure sensor 65A that detects either the meter-in pressure or the meter-out pressure of the slewing motor 11, and a second pressure sensor 65B that detects the other of the meter-in pressure or the meter-out pressure of the slewing motor 11. The boom holding pressure detector 66 is a pressure sensor that detects the pressure (holding pressure) in the head chamber of the boom cylinder 7. 【0049】 The attitude detector 67 detects the attitude of the work device 3. Specifically, in this embodiment, the attitude detector 67 includes a boom attitude sensor 67A for detecting the attitude of the boom 4, an arm attitude sensor 67B for detecting the attitude of the arm 5, and a bucket attitude sensor 67C for detecting the attitude of the bucket 6 (see Figure 1). 【0050】 The boom attitude sensor 67A may be, for example, a boom angle sensor that detects the angle of the boom 4 with respect to the horizontal plane (horizon), a boom angle sensor that detects the angle of the boom 4 with respect to the upper slewing body 2, a stroke sensor that detects the movement of the boom cylinder 7, or any other sensor. Examples of boom angle sensors include resolvers, rotary encoders, potentiometers, and IMUs (inertial measurement units). The stroke sensor may be one that detects the cylinder length of a hydraulic cylinder, or one that detects the position of the piston rod relative to the cylinder tube. 【0051】 The arm attitude sensor 67B may be, for example, an arm angle sensor that detects the angle of the arm 5 with respect to the horizontal plane (horizon), an arm angle sensor that detects the angle of the arm 5 with respect to the boom 4, a stroke sensor that detects the movement of the arm cylinder 8, or any other sensor. The bucket attitude sensor 67C may be a bucket angle sensor that detects the angle of the bucket 6 with respect to the horizontal plane (horizon), a bucket angle sensor that detects the angle of the bucket 6 with respect to the arm 5, a stroke sensor that detects the movement of the bucket cylinder 9, or any other sensor. The arm angle sensor and bucket angle sensor can be the same as those used for the boom angle sensor described above. 【0052】 The attitude detector 67 may further include a slewing body attitude sensor 67D (see Figure 1). The slewing body attitude sensor 67D is a sensor for detecting the attitude of the upper slewing body 2. The slewing body attitude sensor 67D may be, for example, a sensor that detects the inclination (attitude) of the upper slewing body 2 with respect to the horizontal plane. Alternatively, the slewing body attitude sensor 67D may be, for example, a slewing angle sensor that detects the angle (slewing angle) of the upper slewing body 2 with respect to the lower traveling body 1, or a sensor such as a gyro sensor that detects the angular velocity (slewing angular velocity) of the upper slewing body 2 with respect to the lower traveling body 1, or any other sensor. 【0053】 The controller 70 includes a processing unit such as a CPU and an MPU, and memory. The controller 70 controls the operation of the slewing work machine 100 based on detection signals input from multiple detectors. 【0054】 The slewing work machine 100 is equipped with a hydraulic brake circuit that, when decelerating during slewing, returns the hydraulic fluid discharged from the slewing motor 11 and flowing through the meter-out side pipeline (one of the right-slewing pipeline 85 and the left-slewing pipeline 86) to the meter-in side pipeline (the other of the right-slewing pipeline 85 and the left-slewing pipeline 86) to generate a hydraulic brake action by a relief valve. As shown in Figure 2, the hydraulic brake circuit includes a relief valve circuit 81, a check valve circuit 82, a connecting passage 83, and a makeup line 84. 【0055】 The relief valve circuit 81 bypasses the swivel motor 11 and connects the right swivel conduit 85 and the left swivel conduit 86 to each other. The relief valve circuit 81 includes a swivel relief valve 87 and a swivel relief valve 88. The swivel relief valves 87 and 88 are arranged such that the inlet port of the swivel relief valve 87 is connected to the left swivel conduit 86, the inlet port of the swivel relief valve 88 is connected to the right swivel conduit 85, and the outlet ports of the swivel relief valves 87 and 88 are connected to each other. 【0056】 The check valve circuit 82 bypasses the swivel motor 11 and connects the right swivel pipeline 85 and the left swivel pipeline 86 to each other. Specifically, for example, the check valve circuit 82 connects the right swivel pipeline 85 and the left swivel pipeline 86 at a position closer to the swivel motor 11 than the relief valve circuit 81. This check valve circuit 82 includes a swivel check valve 89 and a swivel check valve 90. The swivel check valve 89 is positioned to block the inflow of hydraulic fluid from the right swivel pipeline 85, and the swivel check valve 90 is positioned to block the inflow of hydraulic fluid from the left swivel pipeline 86. 【0057】 The connecting passage 83 connects the portion of the relief valve circuit 81 between the swivel relief valve 87 and the swivel relief valve 88, and the portion of the check valve circuit 82 between the swivel check valve 89 and the swivel check valve 90. The makeup line 84 connects the connecting passage 83 to the tank 99. The makeup line 84 is equipped with a back pressure valve 91 that generates a predetermined back pressure in the makeup line. When the back pressure generated by this back pressure valve 91 becomes negative pressure in the meter-in side pipeline, hydraulic fluid is drawn up to the meter-in side pipeline through the makeup line 84, thereby preventing cavitation. 【0058】 As shown in Figure 4, there are mainly two cases for deceleration during turns. In the first case, as shown in the left diagram of Figure 4, when the turn control lever 41A is returned to the neutral position after a turn operation (right turn operation or left turn operation) has been applied to it, the controller 70 generates a hydraulic brake action in the hydraulic brake circuit to decelerate the turn. The second case differs from the first case, where the turn control lever 41A is returned to the neutral position, in that the turn is decelerated while a turn operation is being applied to the turn control lever 41A. In the second case, when a turn operation is being applied to the turn control lever 41A, and the actual turn speed is greater than the target turn speed corresponding to the amount of the turn operation, the controller 70 generates a hydraulic brake action to decelerate the turn. As a concrete example of this second case, as shown in the right-hand figure of Figure 4, when the amount of rotational operation applied to the rotational operation lever 41A decreases, and the actual rotational speed becomes greater than the target rotational speed corresponding to the reduced amount of operation, the controller 70 generates a hydraulic brake action to decelerate the rotation. 【0059】 First, let's explain the first case. As shown by the dashed line in the left diagram of Figure 4, when the upper slewing body 2 is slewing to the right, for example, when a right slewing operation is applied to the slewing operation lever 41A, as shown by the solid line in the left diagram of Figure 4, when the slewing operation lever 41A is returned to the neutral position, the spool 31B of the slewing control valve 31 returns from the right slewing position to the neutral position. As a result, the slewing control valve 31 blocks the connection between the right slewing pipeline 85 and the left slewing pipeline 86 and the supply pipeline 92 and the return pipeline 93, so the supply of hydraulic fluid from the first pump 21 to the slewing motor 11 and the return of hydraulic fluid from the slewing motor 11 to the tank 99 stop. At this time, the slewing motor 11 continues to rotate in the right slewing direction due to the inertia of the upper slewing body 2. Therefore, the pressure in the left slewing pipeline 86, which is the meter-out side pipeline, increases. When the pressure reaches the set pressure of the swivel relief valve 87, the swivel relief valve 87 opens, and the hydraulic fluid from the left swivel pipeline 86 flows into the swivel motor 11 through the swivel relief valve 87, the connecting passage 83, the swivel check valve 89, and the right swivel pipeline 85. This applies a braking force to the swivel motor 11, which continues to rotate due to inertia, through the action of the relief valve 87, thereby decelerating and stopping the swivel motor 11. In addition, the makeup line 84 prevents cavitation by allowing hydraulic fluid to be drawn up from the makeup line 84 to the connecting passage 83 and the meter-in side pipeline when the meter-in side pipeline becomes negative pressure. The same applies when the swivel operation lever 41A is returned to the neutral position during a left swivel. 【0060】 Next, let's explain the second case. For example, as shown by the dashed line in the right-hand diagram of Figure 4, when the upper rotating body 2 is rotating to the right because a rightward rotation operation of the first lever operation amount (e.g., the maximum operation amount) is applied to the rotation operation lever 41A, if the amount of operation applied to the rotation operation lever 41A decreases from the first lever operation amount to the second lever operation amount (e.g., half the operation amount of the maximum operation amount), as shown by the solid line in the right-hand diagram of Figure 4, the actual rotation speed at that point will be greater than the target rotation speed corresponding to the second lever operation amount. In such a case, the controller 70 slows down the rotation by generating a hydraulic brake action through deceleration control, which will be described later. 【0061】 The slewing work machine 100 is equipped with a slewing control device 101 as shown in Figure 2. The slewing control device 101 includes the first pump 21, the pilot pump 24, the slewing motor 11, the slewing control valve 31, the slewing operator 41, the pair of proportional valves 51, 51, the slewing speed detector 62, the differential pressure detector 65, the boom holding pressure detector 66, the attitude detector 67, the hydraulic brake circuit, and the controller 70. 【0062】 The controller 70 performs deceleration control and constant-speed acceleration control (non-deceleration control). Deceleration control is a control that adjusts the deceleration torque to decelerate the swing motor 11. In other words, deceleration control is a control that adjusts the swing differential pressure (meter-out pressure - meter-in pressure), which is the differential pressure of the swing motor 11 to decelerate the swing motor 11. Constant-speed acceleration control is a control that accelerates the rotation of the swing motor 11 or operates the swing motor 11 at a constant speed. The controller 70 performs the deceleration control while maintaining the state in which the spool 31B of the swing control valve 31 is located within the first operating range. The controller 70 performs the constant-speed acceleration control while maintaining the state in which the spool 31B of the swing control valve 31 is located within the second operating range. 【0063】 The controller 70 determines that the turning motion is in an accelerating constant-velocity state (accelerating state or constant-velocity state) when the actual turning speed is less than or equal to the target turning speed, and performs the accelerating constant-velocity control. The controller 70 determines that the turning motion is in a deceleration state when the actual turning speed is greater than the target turning speed, and performs the deceleration control. 【0064】 If the controller 70 determines that the slewing operation is in an accelerated constant-speed state, it controls the position of the spool 31B of the slewing control valve 31 within the second operating range (within the accelerated constant-speed region) to accelerate the slewing of the upper slewing body 2 or to operate the upper slewing body 2 at a constant speed. In this accelerated constant-speed control, the hydraulic fluid discharged from the first pump 21 is supplied to the slewing motor 11 via the meter-in passage of the slewing control valve 31, and the hydraulic fluid discharged from the slewing motor 11 returns to the tank 99 via the meter-out passage of the slewing control valve 31. 【0065】 If the controller 70 determines that the swing operation is in a deceleration state, it controls the position of the spool 31B of the swing control valve 31 within the first operating range (within the deceleration region) to decelerate the upper swing body 2. In this deceleration control, the meter-in passage of the swing control valve 31 is closed, so that the hydraulic fluid discharged from the first pump 21 is prevented from being supplied to the swing motor 11 via the swing control valve 31. As a result, when the swing motor 11 is decelerated, the differential pressure of the swing motor 11 is not affected by the aforementioned fluctuating factors, namely the discharge amount of hydraulic fluid discharged from the first pump 21 and hydraulic interference. Therefore, when the swing motor 11 is decelerated, it is possible to suppress the meter-in pressure of the swing motor 11 from rising more than necessary due to the aforementioned fluctuating factors. As a result, it is possible to suppress the decrease in the differential pressure (meter-out pressure - meter-in pressure) of the swing motor 11 due to the aforementioned fluctuating factors. 【0066】 In this deceleration control, the controller 70 controls the opening size of the meter-out passage of the swing control valve 31 so that the deceleration torque is equal to the amount of lever operation for the swing operation. 【0067】 Specifically, when deceleration control is performed while the slewing motor 11 is rotating, for example, in a rightward slewing direction, the hydraulic fluid discharged from the slewing motor 11 returns to the tank 99 through the meter-out side pipeline, the leftward slewing pipeline 86, the meter-out passage of the slewing control valve 31, and the return pipeline 93. In this case, the pressure of the hydraulic fluid returning from the slewing motor 11 to the tank 99 is adjusted according to the opening size of the meter-out passage controlled by the controller 70. This increases the pressure in the meter-out side pipeline (leftward slewing pipeline 86), applying a braking force to the slewing motor 11, which continues to rotate due to the inertia of the upper slewing body 2, thereby decelerating the slewing motor 11. Furthermore, when the pressure in the meter-out side pipeline reaches the set pressure of the slewing relief valve 87, the slewing relief valve 87 opens, and the hydraulic fluid from the leftward slewing pipeline 86 flows into the slewing motor 11 through the slewing relief valve 87, the connecting passage 83, the slewing check valve 89, and the rightward slewing pipeline 85. This applies a braking force to the swing motor 11 through the action of the relief valve 87, thereby decelerating the swing motor 11. In addition, the makeup line 84 prevents cavitation by allowing hydraulic fluid to be drawn up from the makeup line 84 into the connecting passage 83 and the right swing pipe 85 when the right swing pipe 85 becomes negative pressure. The same applies when deceleration control is performed when the swing motor 11 is rotating in the left swing direction. 【0068】 Figure 5 shows an example of a map used in deceleration control by the controller 70. Figure 6 shows an example of a map used in constant-speed acceleration control by the controller 70. Figure 5 is a pre-prepared map for adjusting the deceleration torque during deceleration of the swing motor 11 by controlling the opening size of the meter-out passage while the meter-in passage is closed. Figure 6 is a pre-prepared map for accelerating the rotation of the swing motor 11 or rotating the swing motor 11 at a constant speed by controlling the opening sizes of the meter-in passage and the meter-out passage. 【0069】 In Figures 5 and 6, the horizontal axis of the graph represents the valve opening, and the vertical axis represents the current value. In Figure 5, the valve opening is the opening size of the meter-out passage. In Figure 6, the valve opening may be the opening size of the meter-in passage or the opening size of the meter-out passage. 【0070】 When performing deceleration control, the controller 70 determines the current value using the map shown in Figure 5 and inputs the determined current value to the proportional valve 51. This allows the controller to adjust the deceleration torque for decelerating the swing motor 11 while maintaining the state in which the spool 31B of the swing control valve 31 is positioned within the first operating range. 【0071】 When performing constant-speed acceleration control, the controller 70 determines the current value using the map shown in Figure 6 and inputs the determined current value to the proportional valve 51. This allows the spool 31B of the slewing control valve 31 to remain within the second operating range while supplying hydraulic fluid from the pump 21 to the slewing motor 11 to accelerate the rotation of the slewing motor 11 or to operate the slewing motor 11 at a constant speed. 【0072】 Figure 7 is a flowchart showing an example of the calculation process performed by the controller 70 of the turning control device 101 according to this embodiment. The flowchart shown in Figure 7 shows the calculation process for determining the control mode. The control modes include an acceleration constant speed control mode and a deceleration control mode. 【0073】 The controller 70 determines whether or not a slewing operation has been applied to the slewing lever 41A of the slewing control unit 41 (step S11). Specifically, for example, the controller 70 can determine whether or not a slewing operation has been applied to the slewing lever 41A based on the operation signal input from the output unit 41B of the slewing control unit 41. 【0074】 Alternatively, instead of determining whether a rotation operation is being performed on the rotation lever 41A, the controller 70 may determine in step S11 whether the rotation speed is greater than zero. In this case, the controller 70 can determine whether the rotation speed is greater than zero, or in other words, whether the upper rotating body 2 is rotating (whether the rotation motor 11 is rotating), based on the detection signal input from the rotation speed detector 62. 【0075】 If no turning operation is assigned to the turning lever 41A (NO in step S11), the controller 70 sets the constant acceleration flag to OFF and the deceleration flag to OFF (step S17). 【0076】 If a slewing operation is applied to the slewing lever 41A (YES in step S11), the controller 70 calculates the target slewing speed based on the lever operation amount, which is the amount of slewing operation applied to the slewing lever 41A (step S12). Note that the slewing speed is a value correlated with the flow rate of the hydraulic fluid supplied to the slewing motor 11. Therefore, in step S12, instead of calculating the target slewing speed, the controller 70 may calculate the target slewing flow rate, which is the target flow rate of the hydraulic fluid supplied to the slewing motor 11, based on the lever operation amount. 【0077】 The controller 70 pre-stores a map representing the relationship between the lever operation amount for the slewing operation and the target slewing speed (or target slewing flow rate), for example, as shown in Figure 8. The controller 70 can acquire the lever operation amount for the slewing operation based on the slewing operation signal input from the output 41B of the slewing control unit 41. The controller 70 can calculate the target slewing speed (or target slewing flow rate) using the map shown in Figure 8 and the lever operation amount. The controller 70 may, for example, use a pre-set conversion formula to convert the target slewing flow rate to the target slewing speed, or vice versa. 【0078】 The controller 70 acquires the actual turning speed, which is the actual turning speed at that time (step S13). Specifically, the controller 70 receives a detection signal periodically from the turning speed detector 62, so the controller 70 can acquire the actual turning speed at that time. 【0079】 The controller 70 determines whether the actual turning speed is greater than the target turning speed (step S14). 【0080】 If the actual turning speed is greater than the target turning speed (YES in step S14), the controller 70 sets the constant acceleration flag to OFF and the deceleration flag to ON (step S15). This combination of flag settings indicates that the control mode is deceleration control mode. 【0081】 If the actual turning speed is less than or equal to the target turning speed (NO in step S14), the controller 70 sets the constant acceleration flag to ON and the deceleration flag to OFF (step S16). This combination of flag settings indicates that the control mode is constant acceleration control mode. 【0082】 The controller 70 can determine the control mode by performing the calculation process shown in Figure 7 as described above, thereby setting a flag that represents the control mode. 【0083】 Next, the controller 70 performs control according to the flag settings (control according to the control mode), for example, following the flowchart shown in Figure 9. 【0084】 The controller 70 obtains the lever operation amount for the slewing operation applied to the slewing operation lever 41A based on the slewing operation signal input from the output 41B of the slewing control unit 41 (step S31). 【0085】 The controller 70 calculates the target turning flow rate (or target turning speed) using the acquired lever operation amount and the map shown in Figure 8 (step S32). 【0086】 The controller 70 determines whether the constant acceleration flag is set to ON (step S33). If the constant acceleration flag is set to ON (YES in step S33), that is, if the control mode is constant acceleration control mode, the controller 70 performs constant acceleration control (step S35). The controller 70 performs constant acceleration control according to the flowchart shown in Figure 10, for example. 【0087】 If the constant acceleration flag is set to OFF (NO in step S33), the controller 70 determines whether the deceleration flag is set to ON (step S34). If the deceleration flag is set to ON (YES in step S34), that is, if the control mode is deceleration control mode, the controller 70 performs deceleration control (step S36). The controller 70 performs deceleration control according to the flowchart shown in Figure 11, for example. 【0088】 If the deceleration flag is set to OFF (NO in step S34), the controller 70 performs neutral control (step S37). The controller 70 performs neutral control according to the flowchart shown in Figure 12, for example. 【0089】 The following provides a detailed explanation of acceleration constant speed control, deceleration control, and neutral control. 【0090】 [Constant Speed ​​Acceleration Control] Figure 10 is a flowchart showing the calculation process related to constant-velocity acceleration control performed by the controller 70. Constant-velocity acceleration control is performed when the actual turning speed is less than or equal to the target turning speed determined according to the lever operation amount (NO in step S14 of Figure 7). 【0091】 As shown in Figure 10, the controller 70 acquires the actual turning speed at that time using the detection signal input from the turning speed detector 62 (step S41). 【0092】 The controller 70 calculates the actual rotational flow rate, which is the flow rate of the hydraulic fluid actually supplied to the slewing motor 11 (step S42). Specifically, for example, the controller 70 calculates the actual rotational flow rate using the acquired actual rotational speed, the capacity of the slewing motor 11, and the following equation (1). 【0093】 Qsw = qsw × N / 1000 ... (1) In equation (1), Qsw is the actual swirling flow rate, qsw is the capacity of the swivel motor 11, and N is the actual swivel speed. 【0094】 The controller 70 calculates a target valve opening, which is the target valve opening for the swirl control valve 31 (step S43). This target valve opening is a value used to adjust the valve opening of the swirl control valve 31 by feedforward control (FF control). 【0095】 Figure 13 is a map showing the relationship between the target swirl flow rate (or target swirl speed) and the valve opening of the swirl control valve 31. The controller 70 can calculate the target valve opening using the target swirl flow rate (or target swirl speed) calculated in step S32 of Figure 9 and the map shown in Figure 13. 【0096】 The controller 70 calculates a valve command current value (valve command current value for FF control) to adjust the valve opening of the swivel control valve 31 to a target valve opening (step S44). The controller 70 calculates the valve command current value using the map shown in Figure 6, which is prepared in advance for constant-speed acceleration control, and the target valve opening calculated as described above. 【0097】 The controller 70 calculates the target pump flow rate, which is the target flow rate of the hydraulic fluid discharged from the first pump 21 (step S45). Specifically, for example, the controller 70 calculates the target pump flow rate using the actual swirling flow rate (Qsw) calculated as described above and the following equation (2). 【0098】 Qpump = Qsw + α ... (2) In equation (2), Qpump is the target pump flow rate, and α is a value that includes a leak compensation flow rate to compensate for the inevitable leakage of hydraulic fluid from the first pump 21, and a relief compensation flow rate to compensate for the hydraulic fluid returned to the tank 99 through the relief valve. 【0099】 The controller 70 calculates a pump command current value to adjust the flow rate of the hydraulic fluid discharged from the first pump 21 to a target pump flow rate (Qpump) (step S46). Figure 14 is a map showing the relationship between the pump flow rate and the pump command current value. The controller 70 calculates the pump command current value using the calculated target pump flow rate (Qpump) and the map shown in Figure 14. 【0100】 The controller 70 outputs a valve command (right-turn control command or left-turn control command) so that the calculated valve command current value is supplied to the swivel proportional valve 51, and outputs a pump command (pump capacity command) so that the calculated pump command current value is supplied to the regulator of the first pump 21 (step S47). 【0101】 In this constant-speed acceleration control, the controller 70 determines the current value using the map shown in Figure 6 and inputs the determined current value to the proportional valve 51. This maintains the state in which the spool 31B of the slewing control valve 31 is positioned within the second operating range, while supplying hydraulic fluid from the pump 21 to the slewing motor 11 to accelerate the rotation of the slewing motor 11 or to operate the slewing motor 11 at a constant speed. As a result, the upper slewing body 2 rotates while accelerating or rotates at a constant speed due to the slewing motor 11. 【0102】 If the actual turning speed is less than or equal to the target turning speed, constant-speed acceleration control, including the processing in steps S41-S47 of Figure 10 as described above, is performed so that the actual turning speed approaches the target turning speed, or the actual turning speed is maintained at the target turning speed. 【0103】 [Deceleration control] Figure 11 is a flowchart showing the calculation process related to deceleration control performed by the controller 70. Deceleration control is performed when the actual turning speed is greater than the target turning speed determined according to the lever operation amount (YES in step S14 of Figure 7). 【0104】 As shown in Figure 11, the controller 70 obtains the actual rotation speed at that time using the detection signal input from the rotation speed detector 62, and obtains the rotation differential pressure (actual rotation differential pressure), which is the differential pressure of the rotation motor 11 at that time, using the detection signal input from the differential pressure detector 65 (step S61). 【0105】 The controller 70 calculates a target rotational differential pressure (ΔPtgt) according to the lever operation amount (step S62). A specific example of how to calculate the target rotational differential pressure (ΔPtgt) will be described later. The controller 70 can perform control to bring the actual rotational differential pressure of the rotational motor 11 closer to the calculated target rotational differential pressure (ΔPtgt), for example, as follows. 【0106】 The controller 70 calculates the actual rotational flow rate, which is the flow rate of the hydraulic fluid actually supplied to the slewing motor 11 (step S63). The method for calculating this actual rotational flow rate is the same as in step S42 of Figure 10 described above. That is, the controller 70 calculates the actual rotational flow rate using the acquired actual rotational speed, the capacity of the slewing motor 11, and the above equation (1). 【0107】 The controller 70 calculates a target valve opening, which is the target valve opening for the swirl control valve 31 (step S64). This target valve opening is a value used to adjust the valve opening of the swirl control valve 31 by feedforward control (FF control). 【0108】 Specifically, for example, the controller 70 can calculate the target valve opening (Aff) using the actual swirling flow rate (Qsw), the target swirling differential pressure (ΔPtgt), and the following equation (3). 【0109】 Aff=Qsw / (C×√(ΔPtgt)) ···(3) In equation (3), "C" is a predetermined coefficient. 【0110】 The controller 70 calculates a valve command current value (valve command value for FF control) to adjust the valve opening of the swivel control valve 31 to the target valve opening (Aff) (step S65). The controller 70 calculates the valve command current value using the map shown in Figure 5, which is prepared in advance for deceleration control, and the target valve opening calculated as described above. 【0111】 The controller 70 calculates the target pump flow rate, which is the target flow rate of the hydraulic fluid discharged from the first pump 21 (step S66). The method for calculating this target pump flow rate is the same as in step S45 of Figure 10 described above. That is, the controller 70 calculates the target pump flow rate using the actual swirling flow rate (Qsw) calculated as described above and equation (2) described above. 【0112】 The controller 70 calculates a pump command current value to adjust the flow rate of the hydraulic fluid discharged from the first pump 21 to a target pump flow rate (Qpump) (step S67). The method for calculating this pump command current value is the same as in step S46 of Figure 10 described above. That is, the controller 70 calculates the pump command current value using the calculated target pump flow rate (Qpump) and the map shown in Figure 14. 【0113】 The controller 70 outputs a valve command (right-turn control command or left-turn control command) so that the calculated valve command current value is supplied to the swivel proportional valve 51, and outputs a pump command (pump capacity command) so that the calculated pump command current value is supplied to the regulator of the first pump 21 (step S68). 【0114】 When the actual turning speed is greater than the target turning speed, deceleration control is performed, including the processing in steps S61-S68 of Figure 11 as described above, so that the meter-in passage of the turning control valve 31 is closed. As a result, when the turning motor 11 is decelerated, the differential pressure of the turning motor 11 is not affected by fluctuating factors such as hydraulic interference and the discharge amount of hydraulic fluid from the hydraulic pump as described above. Therefore, when the turning motor 11 is decelerated, it is possible to suppress the meter-in pressure of the turning motor 11 from rising more than necessary due to the fluctuating factors. As a result, it is possible to suppress the decrease in the differential pressure (meter-out pressure - meter-in pressure) of the turning motor 11 due to the fluctuating factors. Consequently, a decrease in deceleration torque can be suppressed, and a decrease in braking effectiveness can be suppressed. 【0115】 Here, we will explain a specific example of how to calculate the target swirl differential pressure (ΔPtgt). Figure 15 is a flowchart showing an example of the calculation process performed by the controller to calculate the target swirl differential pressure. 【0116】 As shown in Figure 15, the controller 70 acquires various information from multiple detectors in order to calculate the moment of inertia (I) of the rotating body including the upper rotating body 2 and the work device 3 (steps S91, S92). 【0117】 The controller 70 acquires posture information regarding the posture of the slewing work machine 100 using the detection results input from the posture detector 67 (step S91). This posture information includes posture information of the boom 4, posture information of the arm 5, and posture information of the bucket 6. This posture information may further include posture information of the upper slewing body 2. 【0118】 The controller 70 uses the detection result input from the boom holding pressure detector 66 to obtain the pressure (holding pressure) in the head chamber of the boom cylinder 7 (step S92). The weight of the material held in the bucket 6, such as soil, is correlated with the holding pressure and the posture of the work device 3. Therefore, the controller 70 can calculate the weight of the material held using the obtained holding pressure and the posture information of the work device 3, namely the posture information of the boom 4, the posture information of the arm 5, and the posture information of the bucket 6. 【0119】 The controller 70 has pre-stored the characteristic values ​​of the work device 3, namely the characteristic values ​​of the boom 4, arm 5, and bucket 6 (for example, dimensions, weight, center of gravity position, etc.). Therefore, the controller 70 can calculate the center of gravity position of the work device 3 using the posture information of the work device 3, the weight of the object being held, and the aforementioned characteristic values. 【0120】 The controller 70 has pre-stored characteristic values ​​of the upper slewing body 2 (e.g., weight of the upper slewing body 2, center of gravity position, etc.). Therefore, the controller 70 can calculate the position of the combined center of gravity of the rotating body around the pivot axis Z and the combined center of gravity weight (m) of the rotating body by combining the center of gravity of the upper slewing body 2 and the center of gravity of the work device 3. The rotating body includes the upper slewing body 2, the work device 3, and the holding object. The controller 70 can use the position of the combined center of gravity and the position of the pivot axis Z to calculate the combined center of gravity distance (r), i.e., the distance between the pivot axis Z and the combined center of gravity. Then, the controller 70 calculates the combined center of gravity distance (r) and the combined center of gravity weight (m) using the formula "I = mr 2 Using this, the moment of inertia (I) of the rotating body including the upper rotating body 2, the working device 3, and the holding object is calculated (step S93). 【0121】 The controller 70 calculates the target turning deceleration torque (T) (step S94). Specifically, the target turning deceleration torque (T) is given by the formula "T = mr 2 The moment of inertia (I) around the pivot axis Z is given by the equation "I=mr 2This is expressed as "[T = I × dω / dt]". Therefore, the controller can calculate the target turning deceleration torque (T) using the formula "T = I × dω / dt". In this formula, "dω / dt" is the target turning acceleration (target angular acceleration). 【0122】 The controller 70 can determine the target turning acceleration as follows. The controller 70 has a map in advance that shows the relationship between the amount of lever operation applied to the turning lever 41A of the turning control device 41 and the target turning acceleration. Figure 16 is a graph showing an example of such a map. The controller 70 determines the target turning acceleration based on the amount of lever operation applied to the turning lever at that time and the map. Then, the controller 70 calculates the target turning deceleration torque (T) using the target turning acceleration (dω / dt) and the moment of inertia (I) (step S94). 【0123】 The controller 70 calculates the target turning differential pressure (ΔPtgt) (step S95). The controller can calculate the target turning differential pressure (ΔPtgt) using, for example, the formula "ΔPtgt = 2π × I / q × dω / dt". In this formula, the "I × dω / dt" part corresponds to the target turning torque (T) calculated as described above. Also, in this formula, "q" is the equivalent capacity of the turning motor. The equivalent capacity of the turning motor (q) is the motor capacity including the reduction ratio (q = motor capacity × reduction ratio). The controller 70 stores the equivalent capacity of the turning motor (q). Therefore, the target turning differential pressure (ΔPtgt) can be calculated using the formula "ΔPtgt = 2π × T / q". 【0124】 Furthermore, the calculation method for the target rotational differential pressure (ΔPtgt) is not limited to the above specific example, but may also be a calculation method relating to the following modified example. 【0125】 In this modified example, the controller 70 pre-stores a reference moment of inertia, which is the moment of inertia about the pivot axis Z in the reference posture of the rotating body including the upper slewing body 2 and the work device 3. It then calculates the actual moment of inertia about the pivot axis Z in the actual posture of the rotating body and adjusts the deceleration torque in the slewing motor 11 using the comparison result between the actual moment of inertia and the reference moment of inertia. 【0126】 Specifically, in the calculation method relating to this modified example, in step S94 of Figure 15, instead of calculating the target turning deceleration torque, the moment of inertia ratio (Ir) is calculated, and the deceleration torque is adjusted using this moment of inertia ratio (Ir). The moment of inertia ratio (Ir) is an example of the comparison result mentioned above. 【0127】 The moment of inertia ratio (Ir) is the ratio of the moment of inertia at a predetermined reference attitude (reference moment of inertia) to the moment of inertia at the current attitude (actual moment of inertia) (Ir = actual moment of inertia / reference moment of inertia). In step S94, the controller 70 calculates this moment of inertia ratio (Ir). Then, using the target turning differential pressure reference value (P0) and the formula "ΔPtgt = Ir × P0", the controller 70 can calculate the target turning differential pressure (ΔPtgt) at the current attitude (step S95). 【0128】 The target turning differential pressure reference value (P0) is the target turning differential pressure at the reference attitude and is pre-set and stored in the controller 70. The reference moment of inertia is also pre-stored in the controller 70. The actual moment of inertia is the moment of inertia (I) calculated as shown in step S93 of Figure 15, as described above. As the actual moment of inertia increases, the required turning deceleration torque (required differential pressure) increases. Therefore, for example, if the actual moment of inertia is greater than the reference moment of inertia, the ratio of moments of inertia (Ir) becomes greater than 1, and the target turning differential pressure (ΔPtgt) becomes greater than the target turning differential pressure reference value (P0). 【0129】 As can be seen from the above formula "ΔPtgt = 2π × I / q × dω / dt", when the equivalent capacity of the slewing motor (q) and the target slewing acceleration (dω / dt) are constant values, the slewing differential pressure is proportional to the actual moment of inertia, which is the moment of inertia (I) at that point in time. Therefore, once the target slewing differential pressure reference value (P0) and the ratio of the moment of inertia of the reference posture to the current posture (Ir) are determined, the controller 70 can calculate the target slewing differential pressure (ΔPtgt) at the current posture using the above formula "ΔPtgt = Ir × P0". By performing the above calculation, the controller 70 can calculate the target slewing differential pressure (ΔPtgt) required at the current posture. In this case, the controller 70 adjusts the deceleration torque taking into account the actual moment of inertia that changes according to the change in posture of the work device 3, so that even if the posture of the work device 3 changes, the slewing motor 11 can be decelerated with an acceleration of deceleration corresponding to the lever operation amount. 【0130】 [Neutral control] Figure 12 is a flowchart showing the calculation process related to neutral control performed by the controller 70. Neutral control is performed when no slewing operation is applied to the slewing lever 41A of the slewing control device 41 (NO in step S11 of Figure 7). 【0131】 If no swivel operation is applied to the swivel operation lever 41A, that is, if the swivel operation lever 41A is in the neutral position, the controller 70 determines a valve command current value (neutral current value) so that the spool 31B of the swivel control valve 31 is in the neutral position (step S81). Also, in this case, since there is no need to supply hydraulic fluid from the first pump 21 to the swivel control valve 31, the controller 70 determines a pump command current value (neutral current value) so that the amount of hydraulic fluid supplied to the swivel control valve 31 is zero (step S82). 【0132】 The controller 70 outputs a valve command so that the determined valve command current value is supplied to the swivel proportional valve 51, and outputs a pump command (pump capacity command) so that the determined pump command current value is supplied to the regulator of the first pump 21 (step S83). 【0133】 If the slewing motor 11 is rotating due to the inertia of the upper slewing body 2 when this neutral control is initiated, a valve command is output in step S83 to position the spool 31B of the slewing control valve 31 in the neutral position, and a braking force is applied to the slewing motor 11 by the action of the relief valve 87 or relief valve 88. As a result, the rotation of the slewing motor 11 is reduced, and then the slewing motor 11 stops. If the slewing motor 11 has already stopped when the neutral control is initiated, the valve command output in step S83 maintains the spool 31B of the slewing control valve 31 in the neutral position. As a result, the slewing motor 11 remains stopped. 【0134】 It is preferable for the controller 70 to mitigate the shock when the swing stops by performing control based on the following transient characteristics in neutral control. That is, when the swing operation lever 41A is returned to the neutral position from a certain lever operation amount while the swing motor 11 is rotating, it is preferable for the controller 70 to control the valve command supplied to the swing proportional valve 51 so that it gradually reaches the neutral current value from the valve command current value corresponding to the lever operation amount. 【0135】 Figure 17 is a flowchart showing a modified example of deceleration control performed by the controller 70. The flowchart in Figure 17 differs from the flowchart in Figure 11 in that it further includes steps S71, S72, and S73. The other steps S61-S68 in Figure 17 are the same as steps S61-S68 in Figure 11. 【0136】 In the deceleration control according to the modified example in Figure 17, in step S65, the controller 70 calculates a valve command current value (valve command value for FF control) to adjust the valve opening of the swivel control valve 31 to the target valve opening (Aff), similar to the deceleration control in Figure 11 (step S65). Hereinafter, this valve command current value for FF control will be represented as "Iff". The controller 70 calculates the valve command current value (Iff) for FF control using the map shown in Figure 5, which has been prepared in advance for deceleration control, and the target valve opening calculated as described above. 【0137】 In this modified example, the controller 70 performs the following calculation steps S71, S72, and S73. Steps S71 and S72 are for calculating the valve command current value (Ifb) for adjusting the valve opening of the swivel control valve 31 by feedback control (FB control). Step S73 is for calculating the final valve command current value (Iout) using the valve command current value (Iff) for FF control and the valve command current value (Ifb) for FB control. Specifically, it is as follows. 【0138】 In step S71, the controller 70 calculates the deviation amount, which is the difference between the target turning differential pressure (ΔPtgt_n) at that time and the actual turning differential pressure (ΔP_n) at that time, using the following equation (4). 【0139】 e(n) = ΔPtgt_n - ΔP_n ... (4) In equation (4) above, "e(n)" is the aforementioned deviation quantity. 【0140】 Next, in step S72, the controller 70 calculates the valve command current value (Ifb) for FB control using the deviation amount (e(n)) and the following equation (5). 【0141】 Ifb=Kp×e(n)+Ki×Σe(n)+Kd×(e(n)-e(n-1)) ···(5) In equation (5) above, "Kp", "Ki", ​​and "Kd" are the PID gains (proportional gain, integral gain, and differential gain), "e(n)" is the deviation amount at that point in time, and "e(n-1)" is the deviation amount in the processing of step S72 one cycle earlier. The PID gains are preset for deceleration control and are stored in the controller 70. 【0142】 Next, in step S73, the controller 70 calculates the final valve command current value (Iout) using the valve command current value (Iff) for FF control, the valve command current value (Ifb) for FB control, and the following equation (6). 【0143】 Iout = Iff + Ifb ... (6) The final valve command current value (Iout) is the swivel control command input to the swivel proportional valve 51. 【0144】 Then, the controller 70 outputs a valve command (right-turn control command or left-turn control command) so that the current of the calculated final valve command current value (Iout) is supplied to the swivel proportional valve 51, and outputs a pump command (pump capacity command) so that the current of the pump command current value calculated in step S67 is supplied to the regulator of the first pump 21 (step S68). 【0145】 In this modified example, when the actual turning speed is greater than the target turning speed, deceleration control is performed that includes not only the processing in steps S61-S68 of Figure 17 as described above, but also the processing in steps S71-S73. In this modified example, deceleration control is performed with the meter-in passage of the turning control valve 31 closed, and this deceleration control includes not only feedforward control but also the feedback control described above. Therefore, the actual turning deceleration torque can be adjusted more precisely to the target turning deceleration torque determined according to the lever operation amount. 【0146】 In this modified example, it is preferable that the controller 70 stores a command current upper limit value (Ilmt_u) in advance. The command current upper limit value (Ilmt_u) is the upper limit of the valve command current value supplied to the swivel proportional valve 51, and is the upper limit of the valve command current value set to maintain the state in which the spool 31B is positioned within the first operating range in the deceleration control of this modified example. It is preferable that the controller 70 calculates the FB command current upper limit value (Ifb_u) using the preset command current upper limit value (Ilmt_u), the valve command current value for FF control (Iff) calculated in step S65 of Figure 17, and the following equation (7). 【0147】 FB command current upper limit (Ifb_u) = command current upper limit (Ilmt_u) - valve command current value (Iff) ... (7) In equation (7), the upper limit of the FB command current (Ifb_u) is a value that changes depending on the magnitude of the valve command current value (Iff), and is a threshold value calculated to maintain the state in which the spool 31B is located within the first operating range in the modified deceleration control. 【0148】 In step S72, if the valve command current value (Ifb) calculated by the controller 70 for FB control exceeds the FB command current upper limit value (Ifb_u), it is preferable to correct the valve command current value (Ifb) to the FB command current upper limit value (Ifb_u). In this case, in step S73, the controller 70 calculates the final valve command current value (Iout) using the valve command current value (Iff) for FF control, the corrected valve command current value (i.e., the FB command current upper limit value (Ifb_u)), and the following equation (6'). 【0149】 Iout = Iff + Ifb_u ... (6') The controller 70 then outputs a valve command so that the calculated final valve command current value (Iout) is supplied to the swivel proportional valve 51. This prevents the valve command current value supplied to the swivel proportional valve 51 from exceeding the command current upper limit value (Ilmt_u) in the deceleration control shown in Figure 17, so that the controller 70 can perform deceleration control while maintaining the spool 31B within the first operating range. 【0150】 Furthermore, in this modified example, it is more preferable that the controller 70 pre-stores the command current lower limit (Ilmt_l). The command current lower limit (Ilmt_l) is the lower limit of the valve command current value supplied to the swing proportional valve 51. It is preferable that the controller 70 calculates the FB command current lower limit (Ifb_l) using the command current lower limit (Ilmt_l), the valve command current value for FF control (Iff) calculated in step S65 of Figure 17, and the following equation (8). 【0151】 FB command current lower limit (Ifb_l) = Command current lower limit (Ilmt_l) - Valve command current value (Iff) ... (8) In equation (8), the lower limit of the FB command current (Ifb_l) is a value (threshold) that changes depending on the magnitude of the valve command current value (Iff). 【0152】 In step S72, if the valve command current value (Ifb) for FB control calculated by the controller 70 is less than the lower limit of the FB command current (Ifb_l), it is preferable to correct the valve command current value (Ifb) to the lower limit of the FB command current (Ifb_l). In this case, in step S73, the controller 70 calculates the final valve command current value (Iout) using the valve command current value (Iff) for FF control, the corrected valve command current value (i.e., the lower limit of the FB command current (Ifb_l)), and the following equation (6''). 【0153】 Iout = Iff + Ifb_l ···(6'') The controller 70 then outputs a valve command so that the calculated final valve command current value (Iout) is supplied to the swivel proportional valve 51. 【0154】 [Differentiation] Although a swivel work machine according to the embodiments of this disclosure has been described above, this disclosure is not limited to the embodiments described above and includes, for example, the following modifications. 【0155】 (A) Regarding the moment of inertia In the above embodiment, the moment of inertia (I) about the pivot axis Z is given by the above equation "I=mr 2 The calculation is performed using the formula, but the method (formula) for calculating the moment of inertia is not limited to the specific example described in the above embodiment. 【0156】 (B) Regarding slewing work machines In the above embodiment, the slewing work machine is a hydraulic excavator, but the slewing work machine according to the present disclosure may be another work machine (for example, a crane) equipped with an upper slewing body that is rotatably supported on the machine body. 【0157】 (C) About the swivel control device In the above embodiment, the slewing control device 41 is composed of a so-called electric lever, and the output device 41B of the slewing control device 41 outputs a slewing operation signal to the controller 70 that corresponds to the lever operation amount of the slewing operation applied to the slewing control lever 41A. However, the slewing control device 41 according to this disclosure is not limited to an electric lever. For example, the slewing control device 41 may be equipped with a remote control valve, in which case the output device 41B of the slewing control device 41 includes the remote control valve that outputs a secondary pressure corresponding to the lever operation amount, and a pressure sensor that detects the secondary pressure, and the pressure sensor outputs a detection signal corresponding to the secondary pressure, i.e., a slewing operation signal corresponding to the lever operation amount, to the controller 70. 【0158】 (D) Regarding the pilot pressure control valve In the above embodiment, each of the multiple pilot pressure control valves is composed of an electromagnetic proportional valve, but each of the pilot pressure control valves is not limited to an electromagnetic proportional valve, as long as it outputs a secondary pressure obtained by reducing the pressure of the pressurized oil of the pilot pump 24 in response to a control command input from the controller 70. [Explanation of symbols] 【0159】 1: Lower vehicle (an example of a vehicle) 2: Upper rotating body 3: Work equipment 11: Swivel motor 21: First pump (hydraulic pump) 31: Swivel control valve 31B: Spool of a swivel control valve (an example of a valve body) 41: Swivel control device 51: Proportional valve (an example of a pilot pressure regulating valve) 62: Swing speed detector 65: Differential pressure detector 66: Boom holding pressure detector 67: Attitude detector 70: Controller 100: Swivel work machine 101: Swing control device Z: Rotation axis

Claims

[Claim 1] A slewing control device for a slewing work machine comprising a machine body, an upper slewing body rotatably supported on the machine body, and a work device supported on the upper slewing body, A hydraulic pump that discharges hydraulic fluid, A swing motor that operates when the aforementioned hydraulic fluid is supplied, A swing control valve interposed between the hydraulic pump and the swing motor, A swing control device that receives swing operations from an operator, The system includes a controller that performs deceleration control to adjust the deceleration torque for decelerating the aforementioned swing motor, The swivel control valve has a single valve body capable of operating within a range that includes a first operating range in which the meter-out passage is opened and the meter-in passage is closed, and a second operating range in which both the meter-out passage and the meter-in passage are opened. The controller is a slewing control device that performs the deceleration control while maintaining the state in which the single valve body is positioned within a first operating range. [Claim 2] A slewing control device for a slewing work machine comprising a machine body, an upper slewing body rotatably supported on the machine body, and a work device supported on the upper slewing body, A hydraulic pump that discharges hydraulic fluid, A swing motor that operates when the aforementioned hydraulic fluid is supplied, A swing control valve interposed between the hydraulic pump and the swing motor, A swing control device that receives swing operations from an operator, The system includes a controller that performs deceleration control to adjust the deceleration torque for decelerating the aforementioned swing motor, The swivel control valve has a valve body that can operate within a range that includes a first operating range in which the meter-out passage is opened and the meter-in passage is closed, and a second operating range in which both the meter-out passage and the meter-in passage are opened. The controller is configured to perform the deceleration control while maintaining the state in which the valve body is positioned within the first operating range. A slewing control device is configured to store in advance a reference moment of inertia, which is the moment of inertia about the pivot axis in a reference posture of the rotating body including the upper slewing body and the working device, and in the deceleration control, calculate the actual moment of inertia, which is the moment of inertia about the pivot axis in the actual posture of the rotating body, and control the opening size of the meter-out passage of the slewing control valve using the comparison result between the actual moment of inertia and the reference moment of inertia. [Claim 3] The turning control device according to claim 1, wherein the controller determines a target turning speed according to the amount of the turning operation, and performs the deceleration control when the actual turning speed is greater than the target turning speed. [Claim 4] The swing control device according to claim 1, wherein the controller controls the opening size of the meter-out passage of the swing control valve so that the reduction torque is equal to the amount of the swing operation in the deceleration control. [Claim 5] The slewing control device according to claim 4, wherein the controller pre-stores a reference moment of inertia, which is the moment of inertia about the pivot axis in a reference posture of the rotating body including the upper slewing body and the working device, calculates the actual moment of inertia, which is the moment of inertia about the pivot axis in the actual posture of the rotating body, and adjusts the deceleration torque using the comparison result between the actual moment of inertia and the reference moment of inertia. [Claim 6] A rotating work machine comprising a rotating control device according to any one of claims 1 to 5, the machine body, the upper rotating body, and the work device.

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