Regeneration control device for construction machine

Abstract

A regeneration control device is provided with: an arm cylinder (27); a regeneration circuit (70) that can be switched between a regeneration state and a regeneration release state; and a controller (90) that, when the regeneration circuit (70) is transitioned from the regeneration state to the regeneration release state, controls the regeneration circuit (70) such that, when a predetermined determination condition for determining that a specific work for storing the object in the bucket (24) is not satisfied, transitions from the regeneration state to the regeneration release state are performed with a first responsiveness, and when a predetermined determination condition for determining that the object is stored in the bucket (24) is not satisfied, transitions from the regeneration state to the regeneration release state are performed with a second responsiveness. When the determination condition is satisfied, a transition from the regeneration state to the regeneration release state is performed with a second responsiveness higher than the first responsiveness.

Description

Technical Field

[0001] The present disclosure relates to a regeneration control device for construction machinery such as a hydraulic excavator. Background Art

[0002] Construction machinery such as hydraulic excavators is equipped with a working device comprising a boom, an arm, and a bucket, and uses this working device to perform various operations. The operator applies lever manipulation to the operating lever to cause the working device to perform the required motion for each of the various operations. The controller of the construction machinery controls the motion of the working device based on the lever manipulation. For example, Patent Document 1 discloses a hydraulic control device for a hydraulic excavator that enables simple and reliable horizontal retraction operations.

[0003] However, construction machinery equipped with a regenerative circuit sometimes performs a regenerative operation related to the drive of the arm cylinder, known as arm regeneration. This operation involves resupplying at least a portion of the hydraulic fluid discharged from the rod-side chamber of the arm cylinder to the head-side chamber of the arm cylinder when the arm cylinder is extended to move the arm toward the retraction direction, rather than returning the fluid to the tank. This arm regeneration can accelerate the retraction of the arm.

[0004] The controller of the construction machine performs control based on the state of the hydraulic circuit (eg, pump pressure) that fluctuates during operation, switching between a regeneration state in which the arm regenerates and a regeneration-disabled state in which the arm regenerates.

[0005] However, if the resistance of the soil acting on the arm through the bucket fluctuates during operation, the state of the hydraulic circuit (e.g., pump pressure) will also fluctuate. This can cause a problem in which the regenerative circuit frequently switches between the regenerative state and the regenerative disabling state in a short period of time (so-called hunting). To prevent this problem, it is necessary to reduce the responsiveness of the regenerative circuit when it switches from the regenerative state to the regenerative disabling state. However, reducing the responsiveness of the regenerative circuit also leads to a decrease in energy efficiency.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 11-21941 Summary of the Invention

[0009] An object of the present disclosure is to provide a regeneration control device for a construction machine that can suppress fluctuations in the construction machine that performs an arm regeneration operation and improve energy efficiency.

[0010] A regeneration control device for a construction machine is provided, comprising: an arm cylinder that operates in response to a supply of hydraulic oil discharged from a pump, thereby moving an arm; a regeneration circuit that is switchable between a regeneration state and a regeneration release state, wherein the regeneration state is a state in which an opening of an hydraulic oil flow path for returning hydraulic oil discharged from the arm cylinder, i.e., the discharged hydraulic oil, to a tank is reduced so that at least a portion of the discharged hydraulic oil is resupplied to the arm cylinder through the regeneration flow path; and a regeneration release state is a state in which the opening is increased compared to the regeneration state, thereby releasing the regeneration state; and a controller that, when transitioning the regeneration circuit from the regeneration state to the regeneration release state, controls the regeneration circuit so that, when a predetermined determination condition for determining a specific operation of storing an object in a bucket is not satisfied, the transition from the regeneration state to the regeneration release state is performed with a first responsiveness, and when the determination condition is satisfied, the transition from the regeneration state to the regeneration release state is performed with a second responsiveness that is higher than the first responsiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a side view showing a hydraulic excavator which is a construction machine equipped with the regeneration control device according to the embodiment of the present disclosure.

[0012] Figure 2 It is a diagram showing a hydraulic circuit mounted on the hydraulic excavator.

[0013] Figure 3 This is a block diagram showing the main functions of the controller of the regeneration control device.

[0014] Figure 4 This is a diagram illustrating the operation of the working device during excavation work.

[0015] Figure 5 It is a diagram for explaining the operation of the working device during the horizontal retraction operation.

[0016] Figure 6 This is a diagram illustrating the operation of the working device during compaction and leveling work.

[0017] Figure 7 This is a graph showing an example of temporal changes in the lever operation amount for each of the excavation operation, the horizontal retraction operation, and the compaction and grading operation.

[0018] Figure 8 It is a diagram for explaining the pump pressure, the regeneration release flag, the meter-out opening degree, and the meter-out loss in excavation work using a construction machine according to a reference example.

[0019] Figure 9It is a diagram for explaining the regeneration cancellation response characteristics, pump pressure, regeneration cancellation flag, meter-out opening degree, and meter-out loss in excavation work using the construction machine according to the embodiment.

[0020] Figure 10 This is a flowchart showing the arithmetic control processing performed by the controller.

[0021] Figure 11 This is a flowchart showing a modified example of the arithmetic control processing performed by the controller.

[0022] Figure 12 Graph showing the relationship between the lever operation amount and the response characteristics of the bucket operation in the above-described modification. DETAILED DESCRIPTION

[0023] Embodiments of the present disclosure are described with reference to the accompanying drawings.

[0024] Figure 1 The regeneration control device according to this embodiment is shown as a construction machine, namely a hydraulic excavator 100. Furthermore, the regeneration control device according to the present disclosure is not limited to the hydraulic excavator 100 shown here, but can be widely applied to construction machines that include a machine body and a working device and are primarily powered by hydraulic pressure.

[0025] The hydraulic excavator 100 includes a lower traveling body 10 that can travel on the ground G, an upper rotating body 12 supported by the lower traveling body 10, and a working device 14 supported by the upper rotating body 12. The upper rotating body 12 includes a rotating frame 15, which is supported on the lower traveling body 10 so as to be rotatable around a longitudinal axis Z. The upper rotating body 12 also includes a plurality of elements supported by the rotating frame 15, including a cab 16 and an engine room 18 that accommodates an engine, etc. The working device 14 includes a boom 20, an arm 22, and a bucket 24. In this embodiment, the front-rear direction X is defined based on the orientation of the upper rotating body 12.

[0026] The boom 20 has a base end portion mounted to the front end of the upper slewing body 12 so as to be rotatable about a horizontal axis in both the boom-raising and boom-lowering directions, and a distal end portion opposite the base end portion. The boom-raising direction is the direction in which the boom 20 rotates so that the distal end portion of the boom 20 is clear of the ground G, while the boom-lowering direction is the direction opposite to the boom-raising direction.

[0027] The arm 22 has a base end portion mounted to the distal end of the boom 20 so as to be rotatable about a horizontal axis in both the arm-retracting direction and the arm-pushing direction, and a distal end portion opposite the base end portion. The arm-retracting direction is the direction in which the arm 22 rotates so that the distal end of the arm 22 moves rearward toward the boom 20, while the arm-pushing direction is the direction opposite to the arm-retracting direction.

[0028] Bucket 24 has a base end portion mounted to the distal end of arm 22 so as to be rotatable about a horizontal axis in both the bucket digging direction and the bucket expansion direction, and a distal end portion 24E opposite the base end portion. The bucket digging direction is the direction in which bucket 24 rotates so that distal end portion 24E of bucket 24 approaches upper slewing body 12 or boom 20. The bucket expansion direction is the direction of rotation opposite to the bucket digging direction. Bucket 24 has a bottom surface 24S used in the compaction and leveling operation described later.

[0029] The hydraulic excavator 100 further includes a plurality of working actuators for hydraulically operating the working mechanism 14, and a slewing motor 30 for hydraulically rotating the upper slewing structure 12. The plurality of working actuators include a boom cylinder 26 for operating the boom 20, an arm cylinder 27 for operating the arm 22, and a bucket cylinder 28 for operating the bucket 24. Each of these cylinders 26-28 is a hydraulic cylinder that extends and retracts by receiving a supply of hydraulic oil.

[0030] The boom cylinder 26 is connected to the boom 20 and the upper swing body 12 so that the boom 20 rises and falls as the boom cylinder 26 is extended or retracted, that is, so that the boom 20 is rotated in the boom-raising direction and the boom-lowering direction, respectively. The arm cylinder 27 is connected to the arm 22 and the boom 20 so that the arm 22 is rotated in the arm-retracting direction and the arm-pushing direction, respectively, as the arm cylinder 27 is extended or retracted. The bucket cylinder 28 is connected to the arm 22 and the bucket 24 so that the bucket 24 is rotated in the bucket digging direction and the bucket extending direction, respectively, as the bucket cylinder 28 is extended or retracted.

[0031] The swing motor 30 is a hydraulic motor having an output shaft connected to the upper swing body 12 via a speed reducer (not shown). The swing motor 30 receives a supply of hydraulic oil and rotates the output shaft in a direction corresponding to the supply of hydraulic oil, thereby rotating the upper swing body 12 in the left and right directions.

[0032] The hydraulic excavator 100 includes a hydraulic circuit. Figure 2As shown, the hydraulic circuit includes a portion for rotating the boom 22 and a portion for rotating the bucket 24. These portions include the boom cylinder 27, bucket cylinder 28, first main pump 31, second main pump 32, pilot pump 33, operating device, boom control valve 41, bucket control valve 42, regeneration switching valve 72, and regeneration operation valve 74 (meter-out opening adjustment valve). The operating device includes the boom operator 34 and bucket operator 35. The boom operator 34 receives boom retraction and boom extension operations, while the bucket operator 35 receives bucket excavation and bucket expansion operations.

[0033] The first main pump 31, the second main pump 32, and the pilot pump 33 are all driven by the engine, thereby discharging the oil in the oil tank. The first main pump 31 is a hydraulic pump connected to the boom cylinder 27 and discharging the working oil to be supplied to the boom cylinder 27. The second main pump 32 is a hydraulic pump connected to the bucket cylinder 28 and discharging the working oil to be supplied to the bucket cylinder 28. The pilot pump 33 is a hydraulic pump that discharges the working oil in the oil tank as pilot oil to generate a pilot pressure to be supplied to the boom control valve 41, a pilot pressure to be supplied to the bucket control valve 42, and a pilot pressure to be supplied to the regeneration switching valve 72. Each of the first main pump 31 and the second main pump 32 involved in this embodiment is a variable capacity hydraulic pump, and may also be a fixed capacity hydraulic pump.

[0034] The arm cylinder 27 includes a cylinder body 27a, a piston 27b, and a cylinder rod 27c. The cylinder body 27a surrounds a cylinder chamber. The piston 27b is installed in the cylinder chamber, dividing the cylinder chamber into a head-side chamber 27d and a rod-side chamber 27e. The cylinder rod 27c extends from the piston 27b through the rod-side chamber 27e and protrudes outside the cylinder body 27a. When hydraulic oil is supplied to the head-side chamber 27d, the piston 27b and cylinder rod 27c advance, extending the arm cylinder 27 as a whole. This rotates the arm 22 toward the retracting direction, while the hydraulic oil in the rod-side chamber 27e is discharged. Conversely, when hydraulic oil is supplied to the rod-side chamber 27e, the piston 27b and cylinder rod 27c retract, contracting the arm cylinder 27 as a whole. This rotates the arm 22 toward the pushing direction, while the hydraulic oil in the head-side chamber 27d is discharged.

[0035] The bucket cylinder 28 consists of a cylinder body 28a, a piston 28b, and a cylinder rod 28c. The cylinder body 28a encloses a cylinder chamber. The piston 28b is installed in the cylinder chamber, dividing it into a head-side chamber 28d and a rod-side chamber 28e. The cylinder rod 28c extends from the piston 28b through the rod-side chamber 28e and protrudes outside the cylinder body 28a. When hydraulic oil is supplied to the head-side chamber 28d, the piston 28b and cylinder rod 28c advance, extending the bucket cylinder 28 as a whole. This rotates the bucket 24 in the bucket digging direction while the hydraulic oil in the rod-side chamber 28e is discharged. Conversely, when hydraulic oil is supplied to the rod-side chamber 28e, the piston 28b and cylinder rod 28c retract, contracting the bucket cylinder 28 as a whole. This rotates the bucket 24 in the bucket expansion direction while the hydraulic oil in the head-side chamber 28d is discharged.

[0036] Each of the arm control valve 41 and bucket control valve 42 is a hydraulic pilot switching valve. Receiving a pilot pressure from the pilot pump 33, they operate in an opening direction with a stroke corresponding to the magnitude of the pilot pressure. Consequently, the arm control valve 41 allows hydraulic oil to be supplied to either the head-side chamber 28d or the rod-side chamber 28e of the arm cylinder 27 at a flow rate corresponding to the pilot pressure. The bucket control valve 42 allows hydraulic oil to be supplied to either the head-side chamber 28d or the rod-side chamber 28e of the bucket cylinder 28 at a flow rate corresponding to the pilot pressure.

[0037] The hydraulic circuit includes a central bypass line 51, a supply line 52, a boom return line 53, and a boom push return line 54 as flow paths for the hydraulic oil ejected from the first main pump 31. The central bypass line 51 is configured to reach the oil tank from the discharge port of the first main pump 31, and the boom control valve 41 is configured midway in the central bypass line 51. The supply line 52 is a line that allows the hydraulic oil ejected from the first main pump 31 to be supplied to the boom control valve 41. The supply line 52 branches from the central bypass line 51 at a position upstream of the boom control valve 41 and reaches the inlet port of the boom control valve 41.

[0038] The arm retraction return line 53 is a line for guiding the hydraulic fluid discharged from the arm cylinder 27 when the arm 22 is rotated in the arm retraction direction to the oil tank. The arm push return line 54 is a line for guiding the hydraulic fluid discharged from the arm cylinder 27 when the arm 22 is rotated in the arm push direction to the oil tank.

[0039] The arm control valve 41 is a three-position pilot switching valve having an arm retraction pilot port 41a and an arm push pilot port 41b. When the pilot pressures supplied to the arm retraction pilot port 41a and the arm push pilot port 41b, respectively, are both zero or very low, the arm control valve 41 is held in a neutral position 41N. This blocks the connection between the first main pump 31 and the arm cylinder 27, unblocking the center bypass line 51 and allowing the hydraulic oil from the first main pump 31 to be released directly into the tank.

[0040] After a certain level of arm closure pilot pressure is supplied to the arm closure pilot port 41a, the arm control valve 41 moves from the neutral position 41N to the arm closure position 41A with a stroke corresponding to the magnitude of the arm closure pilot pressure. At this arm closure position 41A, a flow path is formed that allows hydraulic oil from the first main pump 31 to be supplied to the head-side chamber 27d of the arm cylinder 27 at a flow rate corresponding to the stroke, and guides hydraulic oil discharged from the rod-side chamber 27e of the arm cylinder 27 to the arm closure return line 53. Specifically, the arm control valve 41 connects the supply line 52 to the head-side chamber line 55 connected to the head-side chamber 27d, and connects the rod-side chamber line 56 connected to the rod-side chamber 27e to the arm closure return line 53. As a result, the arm cylinder 27 is extended at a speed corresponding to the stroke, the arm 22 is rotated in the arm retraction direction, and the hydraulic oil discharged from the arm cylinder 27 flows to the arm retraction return line 53 .

[0041] Conversely, after a certain level of arm push pilot pressure is supplied to the arm push pilot port 41b, the arm control valve 41 moves from the neutral position 41N to the arm push position 41B with a stroke corresponding to the magnitude of the arm push pilot pressure. At the arm push position 41B, a flow path is formed that allows hydraulic oil from the first main pump 31 to be supplied to the rod-side chamber 27e of the arm cylinder 27 at a flow rate corresponding to the stroke, and guides the discharged hydraulic oil from the head-side chamber 27d of the arm cylinder 27 to the arm push return line 54. Specifically, the arm control valve 41 connects the supply line 52 and the rod-side chamber line 56, and connects the head-side chamber line 55 to the arm push return line 54. As a result, the arm cylinder 27 contracts in the arm push direction at a speed corresponding to the stroke, the arm 22 rotates in the arm push direction, and the hydraulic oil discharged from the arm cylinder 27 flows to the arm push return line 54 .

[0042] The hydraulic circuit includes a center bypass line 61, a supply line 62, and a bucket return line 63 as flow paths for the hydraulic fluid discharged from the second main pump 32. The center bypass line 61 is routed from the discharge port of the second main pump 32 to the oil tank, with the bucket control valve 42 disposed midway along the center bypass line 61. The supply line 62 allows the hydraulic fluid discharged from the second main pump 32 to be supplied to the bucket control valve 42. The supply line 62 branches from the center bypass line 61 upstream of the bucket control valve 42 and reaches the inlet port of the bucket control valve 42. The bucket return line 63 guides the discharged hydraulic fluid from the bucket cylinder 28 to the oil tank.

[0043] The bucket control valve 42 is a three-position pilot switching valve having a bucket excavation pilot port 42a and a bucket deployment pilot port 42b. When the pilot pressures supplied to the bucket excavation pilot port 42a and the bucket deployment pilot port 42b, respectively, namely the bucket excavation pilot pressure and the bucket deployment pilot pressure, are both zero or very low, the bucket control valve 42 is held in a neutral position 42N, blocking the connection between the second main pump 32 and the bucket cylinder 28 and unblocking the center bypass line 61. This allows the hydraulic oil from the second main pump 32 to be released directly to the tank.

[0044] When a bucket excavation pilot pressure exceeding a certain level is supplied to the bucket excavation pilot port 42a, the bucket control valve 42 moves from the neutral position 42N to the bucket excavation position 42A with a stroke corresponding to the magnitude of the bucket excavation pilot pressure. At the bucket excavation position 42A, a flow path is formed that allows hydraulic oil from the second main pump 32 to be supplied to the head-side chamber 28d of the bucket cylinder 28 at a flow rate corresponding to the stroke, and guides hydraulic oil discharged from the rod-side chamber 28e of the bucket cylinder 28 to the return line 63. Specifically, the bucket control valve 42 connects the supply line 62 to a head-side chamber line 65 connected to the head-side chamber 28d, and connects a rod-side chamber line 66 connected to the rod-side chamber 28e to the return line 63. As a result, the bucket cylinder 28 is extended at a speed corresponding to the stroke, the bucket 24 is rotated in the bucket excavation direction, and the hydraulic oil discharged from the bucket cylinder 28 flows to the return line 63 .

[0045] Conversely, after a bucket deployment pilot pressure exceeding a certain level is supplied to the bucket deployment pilot port 42b, the bucket control valve 42 shifts from the neutral position 42N to the bucket deployment position 42B with a stroke corresponding to the magnitude of the bucket deployment pilot pressure. At this bucket deployment position 42B, a flow path is formed that allows hydraulic oil from the second main pump 32 to be supplied to the rod-side chamber 28e of the bucket cylinder 28 at a flow rate corresponding to the stroke, while also directing hydraulic oil discharged from the head-side chamber 28d of the bucket cylinder 28 to the return line 63. Specifically, the bucket control valve 42 connects the supply line 62 and the rod-side chamber line 66, and connects the head-side chamber line 65 to the return line 63. This causes the bucket cylinder 28 to retract in the bucket deployment direction at a speed corresponding to the stroke, causing the bucket 24 to rotate in the bucket deployment direction, while also allowing hydraulic oil discharged from the bucket cylinder 28 to flow to the return line 63.

[0046] The arm operator 34 includes an arm lever 34a and an arm pilot valve 34b and is provided in the cab 16 so that the arm lever 34a can be operated by an operator.

[0047] The arm lever 34a is the portion through which an operator applies arm manipulation to extend or retract the arm cylinder 27, thereby rotating the arm 22. The arm lever 34a is connected to the arm pilot valve 34b so as to be rotatable about its base end. The arm manipulation can be performed by rotating the arm lever 34a in one direction to rotate the arm 22 in the arm-retracting direction, or by rotating the arm lever 34a in the direction opposite to the one direction to rotate the arm 22 in the arm-pushing direction.

[0048] The arm pilot valve 34b, together with the pilot pump 33, constitutes the arm command unit. This arm command unit opens and closes the arm control valve 41, causing the arm cylinder 27 to operate in the direction corresponding to the arm operation applied to the arm lever 34a. Specifically, the arm pilot valve 34b has an inlet port connected to the pilot pump 33 and a pair of outlet ports. These outlet ports are connected to the arm retraction pilot port 41a and the arm push pilot port 41b of the arm control valve 41 via the arm retraction pilot line 36A and the arm push pilot line 36B, respectively. When the arm lever 34a is not substantially subjected to the arm operation and is in a neutral position (i.e., when the magnitude of the arm operation is substantially zero), the arm pilot valve 34b remains closed, blocking the pilot pump 33 from the arm retraction pilot port 41a and the arm push pilot port 41b. When the arm lever 34a is rotated from the neutral position (i.e., when an arm operation is applied to the arm lever 34a), the arm pilot valve 34b opens in response to the arm operation, allowing a pilot pressure corresponding to the magnitude of the arm operation to be supplied from the pilot pump 33 to the pilot port corresponding to the direction of the arm operation, either the arm retraction pilot port 41a or the arm push pilot port 41b. Consequently, the arm control valve 41 opens in a direction corresponding to the arm operation applied to the arm lever 34a and by a stroke corresponding to the magnitude of the arm operation.

[0049] The bucket operator 35 includes a bucket lever 35a and a bucket pilot valve 35b. The bucket operator 35 is provided in the cab 16 so that the bucket lever 35a can be operated by the operator.

[0050] The bucket lever 35a is a portion used by the operator to perform bucket operations for extending and retracting the bucket cylinder 28 and rotating the bucket 24. The bucket lever 35a can be connected to the bucket pilot valve 35b centered around the base end of the bucket lever 35a. These bucket operations include bucket digging operations, in which the bucket lever 35a is rotated in one direction to rotate the bucket 24 in the bucket digging direction, and bucket deployment operations, in which the bucket lever 35a is rotated in a direction opposite to the one direction to rotate the bucket 24 in the bucket deployment direction.

[0051] The bucket pilot valve 35b, together with the pilot pump 33, constitutes a bucket command unit. This bucket command unit opens and closes the bucket control valve 42, which operates the bucket cylinder 28 in the direction corresponding to the bucket operation applied to the bucket lever 35a. Specifically, the bucket pilot valve 35b has an inlet port connected to the pilot pump 33 and a pair of outlet ports. These outlet ports are connected to the bucket excavation pilot port 42a and bucket deployment pilot port 42b of the bucket control valve 42 via a bucket excavation pilot line 37A and a bucket deployment pilot line 37B, respectively. When the bucket lever 35a is not substantially subjected to the bucket operation and is in a neutral position, i.e., when the bucket operation is substantially zero, the bucket pilot valve 35b remains closed, blocking the connection between the pilot pump 33 and the bucket excavation pilot port 42a and the bucket deployment pilot port 42b. When the bucket lever 35a is rotated from the neutral position, i.e., when the bucket lever 35a is subjected to bucket operation, the bucket pilot valve 35b opens in response to the bucket operation, allowing a pilot pressure corresponding to the magnitude of the bucket operation to be supplied from the pilot pump 33 to the pilot port corresponding to the direction of the bucket operation, either the bucket excavation pilot port 42a or the bucket deployment pilot port 42b. Consequently, the bucket control valve 42 opens in a direction corresponding to the bucket operation applied by the bucket lever 35a, and by a stroke corresponding to the magnitude of the bucket operation.

[0052] The hydraulic circuit further includes a regeneration circuit 70. When the arm cylinder 27 extends and the arm 22 moves in the arm-retraction direction, the regeneration circuit 70 resupplies a portion of the hydraulic fluid discharged from the rod-side chamber 27e of the arm cylinder 27 to the head-side chamber 27d, thereby accelerating the extension of the arm cylinder 27.

[0053] Specifically, the regeneration circuit 70 includes a regeneration flow path 71 , a regeneration switching valve 72 , and a regeneration operation valve 74 .

[0054] In this embodiment, the regeneration flow path 71 is formed by the arm control valve 41 when the arm is shifted to the arm-retracted position 41A. Specifically, unlike the normal return flow path 43 in the arm-retracted position 41A, the regeneration flow path 71 directs a portion of the discharged hydraulic oil to the head-side chamber line 55 connected to the head-side chamber 27d of the arm cylinder 27. The normal return flow path 43 directs the discharged hydraulic oil, which returns from the rod-side chamber 27e of the arm cylinder 27 via the rod-side chamber line 56 to the arm control valve 41 during the arm-retracted operation, to the arm-retracted return line 53.

[0055] The regeneration switching valve 72 is a switching valve having a regeneration position 72R and a regeneration release position 72C. In this embodiment, it is a two-position pilot switching valve having a regeneration pilot port 72a. The regeneration pilot port 72a is connected to the pilot pump 33 via a regeneration pilot line 73. When no regeneration pilot pressure is supplied to the regeneration pilot port 72a, the regeneration switching valve 72 remains in the regeneration release position 72C. When a regeneration pilot pressure exceeding a certain level is supplied to the regeneration pilot port 72a, the regeneration switching valve 72 moves from the regeneration release position 72C to the regeneration position 72R with a stroke corresponding to the regeneration pilot pressure. When a regeneration pilot pressure exceeding a predetermined level is supplied to the regeneration pilot port 72a, the regeneration switching valve 72 switches to the regeneration position 72R. In other words, the opening of the regeneration switching valve 72 is adjusted continuously or in stages according to the regeneration pilot pressure supplied to the regeneration pilot port 72a.

[0056] In addition, the regeneration switching valve 72 can also be constructed as follows, that is, when the regeneration pilot pressure is not supplied to the regeneration pilot port 72a, it is maintained in the regeneration position 72R, and after a certain regeneration pilot pressure or more is supplied to the regeneration pilot port 72a, it is transferred from the regeneration position 72R to the regeneration release position 72C with a stroke corresponding to the magnitude of the regeneration pilot pressure, and after a regeneration pilot pressure or more than a specified value is supplied to the regeneration pilot port 72a, it is switched to the regeneration release position 72C.

[0057] When switched to regeneration position 72R, the regeneration switching valve 72 throttles the arm retraction return line 53, limiting the flow rate of the discharged hydraulic oil flowing through the arm retraction return line 53, i.e., the arm retraction return flow rate. Consequently, at least a portion of the discharged hydraulic oil flowing into the arm control valve 41 via the rod-side chamber line 56 flows into the regeneration flow path 71 instead of the return flow path 43, and is resupplied to the head-side chamber 27d of the arm cylinder 27. In other words, after the regeneration switching valve 72 is switched to regeneration position 72R, the regeneration circuit 70 switches to a regeneration state, enabling arm regeneration.

[0058] On the other hand, when the regeneration switching valve 72 is switched to the regeneration disabling position 72C, the arm retraction return line 53 is fully opened, removing the restriction on the arm retraction return flow rate. As a result, the pressure in the arm retraction return line 53 becomes sufficiently lower than the pressure in the head chamber line 55, allowing substantially the entire amount of discharged hydraulic oil to flow into the return flow path 43 instead of into the regeneration flow path 71. In other words, when the regeneration switching valve 72 is switched to the regeneration disabling position 72C, the regeneration circuit 70 switches to the regeneration disabling state (regeneration off state), i.e., a state in which arm regeneration is not performed.

[0059] The regeneration operation valve 74 is provided midway along the regeneration pilot line 73. The regeneration operation valve 74 operates to adjust the regeneration pilot pressure supplied to the regeneration pilot port 72a of the regeneration switching valve 72 through the regeneration pilot line 73 in response to a regeneration command signal input from the controller 90, described later. The regeneration operation valve 74 comprises an electromagnetic proportional valve (electromagnetic pressure reducing valve) having an electromagnetic coil 74a. When no regeneration command signal is input to the electromagnetic coil 74a, the regeneration operation valve 74 closes, blocking the supply of regeneration pilot pressure from the pilot pump 33 to the regeneration pilot port 72a of the regeneration switching valve 72. On the other hand, when a regeneration command signal is input to the electromagnetic coil 74a, the regeneration operation valve 74 opens to an opening corresponding to the regeneration command signal, adjusting the regeneration pilot pressure supplied from the pilot pump 33 to the regeneration pilot port 72a of the regeneration switching valve 72.

[0060] The hydraulic excavator according to this embodiment further includes Figure 2 and Figure 3 The multiple sensors and controller 90 are shown. The controller 90 is connected to Figure 2 The hydraulic circuit shown controls the arm regeneration operation. The multiple sensors acquire information necessary for control by the controller 90 and provide this information to the controller 90. These sensors include a pump pressure sensor 81, an arm retraction pilot pressure sensor 82, a bucket excavation pilot pressure sensor 83, and a bucket expansion pilot pressure sensor 84.

[0061] The pump pressure sensor 81 detects the pump pressure, which is the pressure of the hydraulic oil discharged from the first main pump 31. Specifically, the pump pressure sensor 81 is connected to a pump line connected to the discharge port of the first main pump 31. The pump pressure sensor 81, which is comprised of a pressure sensor, converts the pump pressure into an electrical signal, namely a pump pressure detection signal, and inputs it into the controller 90.

[0062] The arm closure pilot pressure sensor 82 is an arm closure operation detector that detects arm closure operation applied by the arm operator 34. Specifically, the arm closure pilot pressure sensor 82 is connected to the arm closure pilot line 36A and detects the arm closure pilot pressure supplied from the arm operator 34 to the arm closure pilot port 41a of the arm control valve 41 via the arm closure pilot line 36A. The arm closure pilot pressure sensor 82, comprised of a pressure sensor, converts the arm closure pilot pressure into an electrical signal, namely, an arm closure pilot pressure detection signal, and inputs it into the controller 90.

[0063] The bucket excavation pilot pressure sensor 83 is a bucket excavation operation detector that detects bucket excavation operation applied by the bucket operator 35. Specifically, the bucket excavation pilot pressure sensor 83 is connected to the bucket excavation pilot line 37A and detects the bucket excavation pilot pressure supplied from the bucket operator 35 to the bucket excavation pilot port 42a of the bucket control valve 42 via the bucket excavation pilot line 37A. The bucket excavation pilot pressure sensor 83 is comprised of a pressure sensor that converts the bucket excavation pilot pressure into an electrical signal, namely, a bucket excavation pilot pressure detection signal, and inputs it to the controller 90.

[0064] The bucket deployment pilot pressure sensor 84 is a bucket deployment operation detector that detects bucket deployment operations performed by the bucket operator 35. Specifically, the bucket deployment pilot pressure sensor 84 is connected to the bucket deployment pilot line 37B and detects the bucket deployment pilot pressure supplied from the bucket operator 35 to the bucket deployment pilot port 42b of the bucket control valve 42 via the bucket deployment pilot line 37B. The bucket deployment pilot pressure sensor 84 is comprised of a pressure sensor that converts the bucket deployment pilot pressure into an electrical signal, namely, a bucket deployment pilot pressure detection signal, and inputs it to the controller 90.

[0065] The controller 90 includes a computer including a CPU (Central Processing Unit), an MPU (Microprocessor Unit), and a memory. Figure 3 The illustrated mode setting unit 91 , response characteristic setting unit 92 , and regeneration control instruction unit 93 function as a function for performing arm regeneration operation control including switching between a regeneration state and a regeneration release state.

[0066] The mode setting unit 91 switches the control mode of the boom regeneration action. The control mode includes a regeneration mode that allows the boom regeneration action, and a regeneration release mode that does not allow the boom regeneration action. When the prescribed flag ON condition is satisfied, the mode setting unit 91 switches the regeneration release flag (regeneration cutoff flag) from "OFF" to "ON". When the regeneration release flag is "ON", the control mode is the regeneration release mode. When the prescribed flag OFF condition is satisfied, the mode setting unit 91 switches the regeneration release flag from "ON" to "OFF". When the regeneration release flag is "OFF", the control mode is the regeneration mode.

[0067] The flag ON condition may also be that the pump pressure exceeds a predetermined set pressure (P_cut1). That is, the mode setting unit 91 may determine whether the pump pressure exceeds the predetermined set pressure (P_cut1) based on the pump pressure detection signal input from the pump pressure sensor 81 to the controller 90, and switch the regeneration cancellation flag from "OFF" to "ON" if the pump pressure exceeds the set pressure (P_cut1).

[0068] The flag OFF condition may be, for example, the condition that the pump pressure falls below a predetermined set pressure (P_cut2). The set pressure (P_cut2) may be the same as or lower than the set pressure (P_cut1). Alternatively, the flag OFF condition may be, for example, the condition that the time elapsed from the time the regeneration cancel flag switched from "OFF" to "ON" exceeds a predetermined flag OFF set time. Alternatively, the flag OFF condition may be, for example, the condition that the amount of arm retraction operation falls below a predetermined flag OFF set value.

[0069] The response characteristic setting unit 92 sets the response characteristics (transition characteristics) of the regeneration circuit 70 when it transitions from the regeneration state to the regeneration release state based on the boom pilot pressure detection signal, bucket excavation pilot pressure detection signal and bucket deployment pilot pressure detection signal input to the controller 90 from the boom pilot pressure sensor 82, bucket excavation pilot pressure sensor 83 and bucket deployment pilot pressure sensor 84.

[0070] Specifically, the response characteristic setting unit 92 sets the response characteristic to a predetermined first response when the predetermined determination conditions for determining an excavation operation (an example of a specific operation) are not met, and sets the response characteristic to a predetermined second response when the determination conditions are met. The second response is set higher than the first response. Excavation is an operation for collecting foundation sand and soil into a bucket. The first response is pre-set to suppress the occurrence of fluctuations during operations other than excavation, specifically, during compaction and leveling operations. The second response is pre-set to improve energy efficiency during excavation.

[0071] The determination condition may be a determination condition including a condition (first determination condition) that the amount of arm-retracting operation applied by the arm operator 34 reaches a predetermined arm setting value or more, and an amount of bucket excavation operation applied by the bucket operator 35 reaches a predetermined bucket setting value or more. Furthermore, the determination condition may be a determination condition including a condition (second determination condition) that the amount of bucket excavation operation reaches a predetermined bucket setting value or more before the amount of arm-retracting operation is maintained at a predetermined arm setting value or more for a predetermined set time.

[0072] In order to control the action of the regeneration operating valve 74, the regeneration control command unit 93 applies a command (regeneration command signal) to the regeneration operating valve 74, thereby adjusting the secondary pressure of the regeneration operating valve 74, that is, the size of the regeneration pilot pressure supplied to the regeneration pilot port 72a of the regeneration switching valve 72 through the regeneration pilot line 73.

[0073] When the mode setting unit 91 sets the control mode to the regeneration mode, that is, when the regeneration cancellation flag is "OFF," the regeneration control command unit 93 inputs a regeneration command signal to the solenoid 74a of the regeneration operation valve 74. This regeneration command signal causes the regeneration pilot pressure for switching the regeneration switching valve 72 to the regeneration position 72R to be supplied from the regeneration operation valve 74 to the regeneration pilot port 72a of the regeneration switching valve 72. As a result, the regeneration switching valve 72 is switched to the regeneration position 72R, and the regeneration circuit 70 is switched to the regeneration state.

[0074] When the control mode set by the mode setting unit 91 switches from the regeneration mode to the regeneration cancel mode, that is, when the regeneration cancel flag switches from "OFF" to "ON," the regeneration control command unit 93 inputs a regeneration command signal to the solenoid 74a of the regeneration operation valve 74. This regeneration command signal causes the regeneration circuit 70 to transition from the regeneration state to the regeneration cancel state according to the response characteristic (first or second response characteristic) set by the response characteristic setting unit 92. Consequently, the secondary pressure of the regeneration operation valve 74 changes at a rate corresponding to the response characteristic, and the opening of the regeneration switching valve 72 changes at a rate corresponding to the response characteristic from the regeneration position 72R to the regeneration cancel position 72C. After the regeneration switching valve 72 switches to the regeneration cancel position 72C, the regeneration circuit 70 switches to the regeneration cancel state.

[0075] The regeneration control command unit 93 can change the response characteristics by varying the amount of change per unit time in the command value input to the solenoid 74a of the regeneration operation valve 74. Specifically, when the response characteristic setting unit 92 sets the response characteristics to the first responsiveness, the regeneration control command unit 93 inputs a regeneration command signal to the solenoid 74a of the regeneration operation valve 74 such that the amount of change per unit time in the command value input to the solenoid 74a reaches a first predetermined value. As a result, the regeneration circuit 70 transitions from the regeneration state to the regeneration disabled state with the first responsiveness. When the response characteristic setting unit 92 sets the response characteristics to the second responsiveness, the regeneration control command unit 93 inputs a regeneration command signal to the solenoid 74a of the regeneration operation valve 74 such that the amount of change per unit time in the command value input to the solenoid 74a reaches a second predetermined value. As a result, the regeneration circuit 70 transitions from the regeneration state to the regeneration disabled state with the second responsiveness. The second predetermined value (the amount of change in the command value per unit time) is a value larger than the first predetermined value (the amount of change in the command value per unit time).

[0076] Examples of the work involving the arm retracting operation of the arm 22 include various works such as excavation, horizontal retraction, and compaction and leveling. Figure 4 1 is a diagram illustrating the operation of the working device 14 during excavation work. Figure 5 1 is a diagram illustrating the operation of the working device 14 during the horizontal retraction operation. Figure 6 It is a diagram for explaining the operation of the working device 14 during the compaction and leveling work. Figure 7 This is a graph showing an example of the temporal change of the amount of operation (lever operation amount) applied by the operator to the operating device for each of the excavation operation, the horizontal recovery operation, and the compaction and leveling operation. Figure 7 In FIG. 1 , the operation amount of the arm retracting operation is indicated by a solid line, and the operation amount of the bucket operation (bucket digging operation or bucket extending operation) is indicated by a dotted line.

[0077] like Figure 4 As shown in FIG, excavation work is an operation to store soil (an example of an object) of the foundation into the bucket 24. Figure 7 As shown in the figure (a) above, during the excavation operation, the operator performs the bucket digging operation almost simultaneously with the start of the bucket arm operation to allow the bucket 24 to penetrate the soil. In addition, during the excavation operation, the operator performs the boom raising operation together with the bucket arm operation and the bucket digging operation to adjust the depth of the bucket 24 penetrating into the soil. Figure 7 As shown in the above figure (a), the operator usually makes the bucket digging operation amount larger in the initial stage of starting the boom retracting operation (initial stage of the digging operation).

[0078] like Figure 5 As shown, the horizontal retraction operation is an operation in which the distal end portion 24E of the bucket 24 moves rearward approximately horizontally along the ground so that the arm retraction action and the boom raising action are performed simultaneously. Figure 7 As shown in the center of the figure (b), the operator usually does not make the bucket digging operation too large in the initial stage of starting the boom retraction operation (the initial stage of the horizontal retraction operation).

[0079] like Figure 6 As shown, the compaction and leveling operation is performed by moving the bottom surface 24S of the bucket 24 to the bottom surface 24S of the bucket 24 (see Figure 1 ) is an operation in which the arm is retracted and the boom is raised simultaneously while the bucket 24 is moved rearward along the ground in a state substantially horizontal to the ground. During this compaction and leveling operation, the operator simultaneously retracts the arm and expands the bucket to maintain the bottom surface 24S of the bucket 24 substantially horizontal to the ground.

[0080] Figure 8 It is a diagram for explaining the pump pressure, the regeneration release flag, the meter-out opening degree, and the meter-out loss in excavation work using a construction machine according to a reference example.

[0081] In the excavation operation involved in this reference example, the operator retracts the dipper arm to allow the bucket 24 to penetrate the soil of the foundation. After the bucket 24 penetrates the soil, a higher pressure is generated in the pump 31 due to the resistance of the soil. When the pump pressure exceeds the set pressure (P_cut1), the controller controls the regeneration release flag to switch from "OFF" to "ON". After the regeneration release flag is switched to "ON", the controller applies a regeneration instruction signal to the solenoid valve (not shown) for increasing the opening (outlet throttling opening) of the working oil flow path, so as to switch the regeneration circuit from the regeneration state to the regeneration release state. The working oil flow path returns the working oil discharged from the dipper arm cylinder, i.e., the discharged working oil, to the oil tank. As a result, the outlet throttling opening increases from Amo1 to Amo2.

[0082] In the excavation work according to the reference example, the response characteristic (transient characteristic) when the meter-out opening increases from Amo1 to Amo2 is set to the first response. This first response is equivalent to Figure 8 The slope of the straight line indicated by the arrow in the second graph from bottom to top. In other words, the first responsiveness is the characteristic of the change in meter-out opening during the transitional phase when the regeneration circuit changes from the regeneration state to the regeneration release state.

[0083] In the initial stage after the excavation operation begins, such as Figure 8As shown in the second graph from bottom to top, the size of the opening of the working oil flow path for returning the working oil discharged from the boom cylinder to the oil tank (the outlet meter opening) has not yet reached the opening Amo2. Therefore, as Figure 8 As shown in the bottom graph in , pressure loss occurs at the opening of the hydraulic oil flow path (meter-out loss). This pressure loss decreases when the opening of the hydraulic oil flow path (meter-out opening) approaches opening Amo2.

[0084] If the response characteristic is set significantly lower than the first responsiveness during horizontal retraction and compaction and leveling operations, fluctuations may occur, causing the regeneration circuit to frequently switch between the regeneration state and the regeneration release state in a short period of time. Therefore, the construction machinery in the reference example prioritizes suppressing fluctuations, and the response characteristic is set to the first responsiveness, which has a slow rate of change in the meter-out opening. Thus, when the response characteristic is set to the first responsiveness when the regeneration circuit transitions from the regeneration state to the regeneration release state, the meter-out opening takes a long time to change to the opening Amo2 in the initial stage after the start of excavation. Therefore, during this transitional stage, the low meter-out opening state persists for a long time, resulting in increased meter-out losses in the retraction boom.

[0085] Figure 9 This is a diagram for explaining the regeneration cancellation response characteristics, pump pressure, regeneration cancellation flag, meter-out opening degree, and meter-out loss during excavation work using the hydraulic excavator 100 equipped with the regeneration control device according to this embodiment. Figure 9 In the figure, the regeneration cancellation response characteristic refers to the response characteristic when transitioning from the regeneration state to the regeneration cancellation state. The meter-out opening refers to the size of the opening of the hydraulic oil flow path that returns the hydraulic oil discharged from the boom cylinder 27 (i.e., the exhausted hydraulic oil) to the tank. The meter-out loss refers to the pressure loss generated at the opening of the hydraulic oil flow path. In this embodiment, the meter-out opening (the size of the hydraulic oil flow path opening) refers to the opening of the regeneration switching valve 72.

[0086] In this embodiment, when the controller 90 changes the regeneration circuit 70 from the regeneration state to the regeneration release state, the controller 90 controls the regeneration circuit 70 in the following manner: when the predetermined determination condition (the first determination condition or the second determination condition) for determining the excavation operation is not satisfied, the controller 90 controls the regeneration circuit 70 so that the regeneration state is changed to the regeneration release state with the first responsiveness; when the determination condition is satisfied, the controller controls the regeneration circuit 70 so that the regeneration state is changed to the regeneration release state with the second responsiveness higher than the first responsiveness. The second responsiveness is higher than the first responsiveness. The second responsiveness is equivalent to Figure 9 The slope of the straight line in the portion indicated by the arrow in the second graph from bottom to top.

[0087] In this embodiment, when performing excavation work among various operations including arm retraction, the controller 90 sets the response characteristics (transient characteristics) when the meter-out opening is increased from Amo1 to Amo2 to Figure 9 The second responsiveness shown in FIG. 1 is set by the controller 90 to be responsive to the following conditions: when performing operations other than excavation operations among various operations including arm retraction, the controller 90 sets the response characteristics to be responsive to the following conditions: Figure 8 In the present embodiment, the operation other than the excavation operation is at least one of a horizontal recovery operation and a compaction and leveling operation.

[0088] In this embodiment, if Figure 7 Figure (a) and Figure 8 As shown in the top figure, the operator performs a bucket arm retraction operation to cause bucket 24 to penetrate the soil of the foundation, allowing work device 14 to perform excavation. As described above, during excavation, the operator performs a bucket digging operation approximately simultaneously with the start of the bucket arm retraction operation to cause bucket 24 to penetrate the soil. After bucket 24 penetrates the soil, the resistance of the soil generates a high pressure in pump 31. When the pump pressure exceeds the set pressure (P_cut1), the mode setting unit 91 of controller 90 controls the regeneration cancellation flag to switch from "OFF" to "ON."

[0089] After the regeneration cancellation flag is switched from "OFF" to "ON", the regeneration control command unit 93 of the controller 90 applies a regeneration command signal (command current) to the regeneration operation valve 74 to switch the regeneration circuit 70 from the regeneration state to the regeneration cancellation state. This regeneration command signal (command current) is used to increase the opening of the working oil flow path for returning the working oil discharged from the boom cylinder 27, that is, the discharged working oil to the oil tank, that is, the opening (outlet meter opening) of the regeneration switching valve 72. In this case, if the operation amount of the boom retraction operation is maintained at or above the boom setting value for a predetermined set time t1 (see Figure 7 ), the controller 90 switches the response characteristic from the first responsiveness to the second responsiveness if the bucket excavation operation amount reaches or exceeds the predetermined bucket setting value (Pi_bk_dig1) before the regeneration command signal is reached. This regeneration command signal is a command current that increases the opening (meter-out opening) of the regeneration switching valve 72 from Amo1 to Amo2 at a change rate determined according to the second responsiveness. As a result, the opening (meter-out opening) of the regeneration switching valve 72 increases from Amo1 to Amo2 according to the second responsiveness.

[0090] As described above, in this embodiment, when excavation is performed, Figure 9As shown in the second graph from the top in FIG, the response characteristic switches from the first response to the second response. Therefore, compared with the case where the response characteristic is maintained at the first response, the duration of the state of the small meter-out opening in the initial stage after the start of the excavation operation can be shortened (refer to Figure 9 The second curve from bottom to top in ). As a result, Figure 9 As shown in the bottom curve graph in , the increase in the boom outlet throttling loss can be suppressed, thereby improving the energy saving of the excavation operation.

[0091] On the other hand, when performing operations other than excavation (horizontal retraction operation or compaction and leveling operation) among various operations including boom retraction, the controller 90 maintains the response characteristic at the first responsiveness and does not switch it to the second responsiveness.

[0092] like Figure 5 and Figure 7 As shown in the center figure (b) in the horizontal retraction operation, the operation amount of the bucket digging operation at the beginning of the bucket arm retraction operation is not too large, and is smaller than the bucket setting value (Pi_bk_dig1). Figure 6 and Figure 7 As shown in the bottommost figure (c) of FIG, during the compaction and leveling operation, the arm retraction operation and the bucket extension operation are performed simultaneously to maintain the bottom surface 24S of the bucket 24 substantially horizontal with the ground. Therefore, the controller 90 can determine that the horizontal retraction operation or the compaction and leveling operation is being performed instead of the excavation operation based on the first or second determination conditions described above.

[0093] During the horizontal retraction operation, when the boom 22 performs the boom retraction action, although the resistance of the soil acts on the boom 22 in the direction opposite to the direction of the boom retraction action, the resistance is small. In addition, the deadweight of the boom 22 acts in the direction along the boom retraction action. Therefore, in the boom cylinder 27, the pressure of the rod side chamber 27e is higher than the pressure of the head side chamber 27d, and the pump pressure becomes below the set pressure (P_cut1). Under this pressure relationship, the boom regeneration action can be performed, and the boom retraction action can be accelerated by the boom regeneration action. Therefore, during the horizontal retraction operation, when the pump pressure is below the set pressure (P_cut1), the controller 90 controls the regeneration release flag to maintain "OFF", thereby performing the boom regeneration action.

[0094] During this horizontal retraction operation, for example, if bucket 24 is blocked by an obstacle such as a rock or stone on the ground, the resistance acting on arm 22 may temporarily increase, and the pump pressure may exceed the set pressure (P_cut1). In this case, controller 90 switches the regeneration cancellation flag from "OFF" to "ON," applying a regeneration command signal (command current) to regeneration operation valve 74 to switch the regeneration circuit from the regeneration state to the regeneration cancellation state. As a result, the meter-out opening gradually increases from Amo1 to Amo2.

[0095] If the response characteristics are still set to the second, more responsive, response during horizontal retraction, the meter-out opening will rapidly increase from Amo1 to Amo2, and the flow rate of hydraulic oil resupplied to the arm cylinder 27 will decrease sharply, causing the speed of the arm retraction operation to drop sharply. In this case, the balance between the boom raising and arm retraction speeds is disrupted, causing the distal end 24E of the bucket 24 to lift off the ground, making it impossible to move the bucket 24 horizontally rearward.

[0096] Therefore, in this embodiment, during horizontal retraction, the response characteristics remain at the first responsiveness and do not switch to the second responsiveness. That is, during horizontal retraction, the regeneration circuit 70 is controlled so that its responsiveness when transitioning from the regeneration state to the regeneration release state is reduced compared to when performing excavation. This prevents a sudden drop in the speed of the arm retraction operation, even if the resistance acting on the boom 22 temporarily increases during the horizontal retraction operation. The balance between the boom raising and boom retraction speeds is thus less likely to be disrupted. This prevents a decrease in the efficiency of the horizontal retraction operation.

[0097] In addition, during the horizontal recovery operation, soil gradually accumulates inside the bucket 24 during the operation. Therefore, in order to scoop out the soil, the operator may sometimes use the bucket 24 in the latter half of the horizontal recovery operation, such as Figure 7 As shown in the center portion (b) of the figure, the bucket digging operation amount is increased. In this case, although the bucket digging operation amount may sometimes exceed the bucket setting value (Pi_bk_dig1), this often occurs in the second half of the horizontal retraction operation. Therefore, when the second judgment condition is used as the judgment condition, even if the bucket digging operation amount increases in the second half of the horizontal retraction operation, that is, after the bucket arm retraction operation has been maintained above the bucket arm setting value for a predetermined set time t1 from the start of the bucket arm retraction operation, the controller 90 can maintain the response characteristic at the first responsiveness without switching it to the second responsiveness.

[0098] During the compaction and leveling operation, as described above, in order to maintain the bottom surface 24S of the bucket 24 approximately horizontal with the ground, the boom retracting operation and the bucket unfolding operation are performed simultaneously. Therefore, the controller 90 controls the response characteristic to maintain the first responsiveness instead of switching it to the second responsiveness based on the above-mentioned first judgment condition or the second judgment condition.

[0099] During the compaction and leveling operation, the force (compacting force) that compacts the bottom surface 24S of the bucket 24 to the ground sometimes changes. When the boom 22 performs the boom retraction action, the resistance of the ground acting on the boom 22 in the direction opposite to the direction of the boom retraction action changes according to the change in the compacting force. When the compacting force is small, the resistance acting on the boom 22 is also small, so the pump pressure becomes below the set pressure (P_cut1). During the compaction and leveling operation, the controller 90 controls the regeneration release flag to maintain "OFF" when the pump pressure is below the set pressure (P_cut1), thereby performing the boom regeneration action. On the other hand, during the compaction and leveling operation, the compacting force increases, the resistance acting on the boom 22 increases, and the pump pressure sometimes exceeds the set pressure (P_cut1). In this case, the controller 90 controls the regeneration release flag to switch from "OFF" to "ON", and applies a regeneration command signal (command current) to the regeneration operation valve 74 for switching the regeneration circuit from the regeneration state to the regeneration release state. As a result, the meter-out opening gradually increases from Amo1 to Amo2.

[0100] Assuming that during the compaction and leveling operation, the response characteristic is still set to the second response with higher responsiveness, the outlet throttle opening will increase rapidly from Amo1 to Amo2, and the flow rate of the working oil supplied to the boom cylinder 27 again will decrease sharply, so the speed of the boom retracting action will drop sharply. In this case, the balance between the speed of the boom raising action and the boom retracting action is destroyed, and the bottom surface 24S of the bucket 24 quickly leaves the ground upward. After the bottom surface 24S of the bucket 24 leaves the ground, the resistance acting on the boom 22 decreases, and the pump pressure becomes below the set pressure (P_cut1). In this case, the controller 90 controls the regeneration release flag to switch from "ON" to "OFF", and applies a regeneration instruction signal (instruction current) to the regeneration operating valve 74 for switching the regeneration circuit from the regeneration release state to the regeneration state. Therefore, when the response characteristic is still set to the second responsiveness with higher responsiveness during the compaction and leveling operation, fluctuations may occur. The fluctuations are caused by the regeneration circuit 70 frequently switching between the regeneration state and the regeneration release state in a short period of time, and the bottom surface 24S of the bucket 24 is repeatedly compacted to the ground and repeatedly leaves the ground.

[0101] Therefore, in this embodiment, when performing compaction and leveling operations, the response characteristics are maintained at the first responsiveness and are not switched to the second responsiveness. That is, when performing compaction and leveling operations, the regeneration circuit 70 is controlled so that the responsiveness of the regeneration circuit 70 when switching from the regeneration state to the regeneration release state is reduced compared to when performing excavation operations. Thus, even when the compaction force changes during the compaction and leveling operations, the speed of the boom retracting action can be suppressed from dropping sharply, and the balance between the speed of the boom raising action and the boom retracting action is not easily disrupted. As a result, fluctuations can be suppressed, thereby suppressing a decrease in the efficiency of the compaction and leveling operations.

[0102] Figure 10 1 is a flowchart showing the calculation control process performed by the controller 90 . Figure 10 The calculation process of represents the flow of setting the response characteristics by the controller 90.

[0103] The response characteristic setting unit 92 of the controller 90 determines whether the amount of operation of the arm retracting operation is greater than the arm setting value (step S11). If the amount of operation of the arm retracting operation is less than the arm setting value (step S11 is "No"), the response characteristic setting unit 92 of the controller 90 sets the response characteristic to the first responsiveness (step S16).

[0104] The controller 90 starts measuring the elapsed time from the time point when the operation amount of the arm retraction operation reaches or exceeds the arm setting value (step S12).

[0105] The response characteristic setting unit 92 of the controller 90 determines whether the operation amount of the bucket excavation operation is greater than the bucket setting value (step S13). If the operation amount of the bucket excavation operation is less than the bucket setting value (step S13: "No"), the response characteristic setting unit 92 of the controller 90 sets the response characteristic to the first responsiveness (step S16).

[0106] On the other hand, if the amount of bucket excavation operation is greater than or equal to the bucket setting value ("Yes" in step S13), the response characteristic setting unit 92 of the controller 90 determines whether the elapsed time is less than a predetermined set time (step S14). If the elapsed time is greater than or equal to the set time ("No" in step S14), the response characteristic setting unit 92 of the controller 90 sets the response characteristic to the first responsiveness (step S16). On the other hand, if the elapsed time is less than the set time ("Yes" in step S14), the response characteristic setting unit 92 of the controller 90 sets the response characteristic to the second responsiveness (step S15).

[0107] Figure 11 This is a flowchart showing a modified example of the calculation control process performed by the controller 90 . Figure 11The calculation process of represents the flow of setting the response characteristics by the controller 90.

[0108] Figure 11 The processing of steps S11 to S14 and S16 in the calculation process of the modification example shown is the same as Figure 10 The processes of steps S11 to S14 and S16 in the illustrated calculation processes are the same, and therefore, description of these processes will be omitted.

[0109] exist Figure 11 In the modified example shown, when the elapsed time is less than the set time ("Yes" in step S14), the response characteristic setting unit 92 of the controller 90 changes the second responsiveness according to the amount of operation of the bucket excavation operation at that time (step S17). Specifically, when it is determined in step S13 that the amount of operation of the bucket excavation operation is greater than the bucket set value (Pi_bk1), and when it is determined in step S14 that the elapsed time is less than the set time, the response characteristic setting unit 92 of the controller 90 changes the second responsiveness according to the amount of operation of the bucket excavation operation at that time (step S17). Figure 12 As shown, the response characteristic setting unit 92 of the controller 90 changes the second responsiveness so that the second responsiveness increases when the operation amount of the bucket excavation operation is large compared to when the operation amount of the bucket excavation operation is small.

[0110] During excavation work (an example of a specific operation) to collect sand (an example of an object) into bucket 24, the operator tends to perform a bucket excavation operation that actively moves bucket 24 in the bucket excavation direction. The amount of bucket excavation operation used becomes an indicator for determining whether excavation is in progress. That is, the likelihood of excavation being in progress is higher when the amount of bucket excavation operation is large than when the amount of bucket excavation operation is small. Therefore, in this modified example, the response characteristic setting unit 92 of controller 90 can switch the regeneration circuit 70 from the regeneration state to the regeneration release state with high responsiveness when the likelihood is high compared to when the likelihood is low. Furthermore, by adjusting the responsiveness based on the amount of bucket excavation operation, it is possible to suppress a decrease in operational feel caused by a sudden change in responsiveness.

[0111] As described above, when performing a specific operation such as excavation to collect soil in the bucket 24, where the pump pressure is maintained high during operation, that is, when the aforementioned determination conditions are met, the controller 90 of the regeneration control device according to this embodiment controls the regeneration circuit to quickly transition from the regeneration state to the regeneration-disabled state with a second responsiveness that is higher than the first responsiveness. This allows the opening of the hydraulic fluid passage, which returns hydraulic fluid discharged from the arm cylinder 27 to the tank, to be quickly switched from a narrow opening to a wide opening, thereby preventing the hydraulic fluid passage from maintaining a narrow opening for a prolonged period during the initial phase after the start of the specific operation, i.e., the transition phase from the regeneration state to the regeneration-disabled state. Consequently, an increase in pressure loss in the hydraulic fluid passage during this transition phase can be suppressed. On the other hand, when performing operations other than specific operations, such as horizontal recovery and compaction and grading, that is, when the aforementioned determination conditions are not met, the controller 90 controls the regeneration circuit to quickly transition from the regeneration state to the regeneration-disabled state with a first responsiveness that is lower than the second responsiveness. In operations other than specific operations such as horizontal retraction operations and compaction and leveling operations, the force acting on the boom 22 from the object sometimes still fluctuates, and this force fluctuation can cause a change in the state of the hydraulic circuit, such as a change in pump pressure. Sometimes, due to such a change in the state of the hydraulic circuit, the regeneration circuit 70 frequently switches between the regeneration state and the regeneration release state in a short period of time. In this case, if the transition from the regeneration state to the regeneration release state is performed with high responsiveness, the fluctuation range of the speed of the boom retraction action is also likely to become large. This causes a decrease in working efficiency. Therefore, when performing operations other than specific operations, the regeneration control device involved in this embodiment controls the regeneration circuit 70 to transition from the regeneration state to the regeneration release state with a first responsiveness that is lower than the second responsiveness. As a result, even when the force acting on the boom 22 from the object fluctuates, the fluctuation range of the speed of the boom retraction action can be suppressed from becoming large. As a result, a decrease in working efficiency when performing operations other than specific operations can be suppressed. As described above, the regeneration control device can improve energy efficiency while suppressing a decrease in working efficiency in the hydraulic excavator 100 that performs an arm regeneration operation.

[0112] [Modification]

[0113] Although the 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 modified examples.

[0114] (A) About the operating device

[0115] The arm operator 34 and bucket operator 35 according to the present disclosure are not limited to including the arm pilot valve 34b and the bucket pilot valve 35b, respectively. At least one of the arm operator and the bucket operator may also include: an electric lever device that generates an electric signal corresponding to an operation performed by an operator and inputs the electric signal to the controller 90; and a pilot pressure command unit included in the controller 90 that inputs a command signal to a solenoid-operated valve in a pilot line based on the electric signal input from the electric lever device, thereby applying a pilot pressure to the pilot port of the arm control valve or the bucket control valve.

[0116] (B) About the regeneration circuit

[0117] The regeneration circuit involved in this disclosure is not limited to Figure 2 The circuit shown in FIG. 4 includes a combination of the arm control valve 41 including the regeneration flow path 71 and the regeneration switching valve 72 for limiting the return flow rate. The regeneration circuit may also include a single regeneration switching valve independent of the arm control valve. Specifically, the switching valve may be switched between a regeneration position, which forms a regeneration flow path for resupplying hydraulic fluid discharged from the arm cylinder to the arm cylinder, and a regeneration release position, which allows the discharged hydraulic fluid to be directly released to the tank.

[0118] (C) Regarding specific operations

[0119] In the above embodiment, the specific operation is excavation of the sand and soil of the foundation. However, the specific operation involved in the present disclosure is not limited to excavation and may also be other operations that involve placing an object in the bucket. Specifically, the object placed in the bucket may be other objects besides sand and soil, such as gravel or waste.

[0120] According to the present disclosure, a regeneration control device for a construction machine is provided, which can suppress fluctuations in the construction machine that performs an arm regeneration operation and improve energy efficiency.

[0121] A regeneration control device for a construction machine is provided, comprising: an arm cylinder that operates in response to a supply of hydraulic oil discharged from a pump, thereby moving an arm; a regeneration circuit that is switchable between a regeneration state and a regeneration release state, wherein the regeneration state is a state in which an opening of an hydraulic oil flow path for returning hydraulic oil discharged from the arm cylinder, i.e., the discharged hydraulic oil, to a tank is reduced so that at least a portion of the discharged hydraulic oil is resupplied to the arm cylinder through the regeneration flow path; and a regeneration release state is a state in which the opening is increased compared to the regeneration state, thereby releasing the regeneration state; and a controller that, when transitioning the regeneration circuit from the regeneration state to the regeneration release state, controls the regeneration circuit so that, when a predetermined determination condition for determining a specific operation of storing an object in a bucket is not satisfied, the transition from the regeneration state to the regeneration release state is performed with a first responsiveness, and when the determination condition is satisfied, the transition from the regeneration state to the regeneration release state is performed with a second responsiveness that is higher than the first responsiveness.

[0122] This regeneration control device rapidly transitions from the regeneration state to the regeneration-disabled state with a second responsiveness when the judgment conditions are met, that is, when performing a specific operation (e.g., excavation) of receiving an object in the bucket. This improves energy efficiency. Furthermore, in this specific operation, the bucket is often subjected to high resistance from the object, which continuously acts on the bucket. Therefore, even with a high responsiveness setting, fluctuations are less likely to occur. On the other hand, when the judgment conditions are not met, the transition from the regeneration state to the regeneration-disabled state is performed with a first responsiveness, which is lower than the second responsiveness, thereby suppressing fluctuations. Therefore, this regeneration control device can suppress fluctuations in construction machinery performing boom regeneration and improve energy efficiency.

[0123] Preferably, the regeneration control device further includes an operating device that receives an arm-retracting operation and a bucket excavation operation, wherein the determination condition includes a condition that the operation amount of the arm-retracting operation reaches or exceeds a predetermined arm setting value, and the operation amount of the bucket excavation operation reaches or exceeds a predetermined bucket setting value. In this configuration, the controller can use the determination condition to appropriately determine whether a specific operation is being performed.

[0124] Preferably, the regeneration control device further includes an operating device that receives an arm-retracting operation and a bucket excavation operation, wherein the determination condition includes a condition that the operation amount of the bucket excavation operation reaches or exceeds a predetermined bucket setting value before a predetermined set time elapses during which the operation amount of the arm-retracting operation remains at or above a predetermined arm setting value. In this configuration, the controller can more appropriately determine whether a specific operation is being performed using the determination condition that includes a time factor.

[0125] Ideally, when the judgment condition is satisfied, the controller changes the second responsiveness so that the second responsiveness increases when the amount of bucket digging operation is large compared to when the amount of bucket digging operation is small. In a specific operation of storing an object in a bucket, the operator tends to perform a bucket digging operation that actively moves the bucket in the bucket digging direction, and the amount of bucket digging operation becomes an indicator for determining whether a specific operation is being performed. That is, when the amount of bucket digging operation is large, the probability of a specific operation being performed is higher than when the amount of bucket digging operation is small. Therefore, in this structure, when the probability is high, the controller can switch the regeneration circuit from the regeneration state to the regeneration release state with high responsiveness compared to when the probability is low. In addition, by adjusting the responsiveness according to the amount of bucket digging operation, it is possible to suppress a decrease in operational feel caused by a sudden change in responsiveness.

Claims

1. A regeneration control device for construction machinery, characterized in that include: The arm cylinder receives the hydraulic oil from the pump and works to move the arm. a regeneration circuit switchable between a regeneration state and a regeneration release state, wherein the regeneration state is a state in which an opening of a working oil flow path for returning working oil discharged from the arm cylinder, i.e., the discharged working oil, to a tank is reduced so that at least a portion of the discharged working oil is resupplied to the arm cylinder through the regeneration flow path; and a regeneration release state in which the opening is increased compared to the regeneration state to release the regeneration state; The controller controls the regeneration circuit in such a manner that, when causing the regeneration circuit to transition from the regeneration state to the regeneration release state, the transition from the regeneration state to the regeneration release state is performed with a first responsiveness when a predetermined determination condition for determining a specific operation of storing an object in a bucket is not satisfied, and the transition from the regeneration state to the regeneration release state is performed with a second responsiveness that is higher than the first responsiveness when the determination condition is satisfied.

2. The regeneration control device for construction machinery according to claim 1, characterized in that Also includes: The operating device accepts the arm retraction operation and bucket digging operation, wherein, The determination conditions include a condition that the operation amount of the arm retracting operation reaches a predetermined arm setting value or more, and the operation amount of the bucket excavation operation reaches a predetermined bucket setting value or more.

3. The regeneration control device for construction machinery according to claim 1, characterized in that Also includes: The operating device accepts the arm retraction operation and bucket digging operation, wherein, The determination condition includes a condition that the operation amount of the bucket excavation operation reaches or exceeds a predetermined bucket setting value before a predetermined setting time elapses in which the operation amount of the arm retracting operation is maintained at or above a predetermined arm setting value.

4. The regeneration control device for construction machinery according to claim 2 or 3, characterized in that: When the determination condition is satisfied, the controller changes the second responsiveness so that the second responsiveness increases when the operation amount of the bucket excavation operation is large compared to when the operation amount of the bucket excavation operation is small.

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