Work machine

Abstract

To perform an excavation operation more efficiently by dissolving an overload condition without interrupting the excavation operation or correcting a locus of the excavation operation when an overload condition due to an excavation reaction force occurs during the excavation operation using a boom and an arm, in an excavation control system for a work machine.SOLUTION: A controller 20 calculates a linear motion force of each of a boom cylinder 2 and an arm cylinder 3 based on detection signals of pressure sensors 25a to 26b during a combined operation of simultaneously driving a boom 105 and an arm 106. When either one of the linear motion forces reaches a limit value, the controller 20 calculates a direction in which the linear motion force reaching the limit value decreases based on detection signals of IMU 27, 28 and the linear motion force, and controls driving of the boom cylinder 2 and the arm cylinder 3 so that an excavation operation point Pw of the front work device 104 moves in that direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a working machine such as a hydraulic excavator equipped with an excavation control system.

Background Art

[0002] In a hydraulic excavator which is a representative example of a working machine, various excavation control systems have been proposed to smoothly perform an excavation operation by causing an appropriate actuator operation based on the operation information of an operator during the excavation operation by the operator. For example, in Patent Document 1, an excavation reaction force acting on a bucket is calculated using an excavation reaction force table from the detected boom angle, arm angle, bucket angle, and earth and sand characteristics stored in a storage device in advance, and it is determined whether or not to correct the excavation operation depending on whether or not the calculated excavation reaction force is greater than a preset upper limit value. Further, in Patent Document 1, it is preferable to notify the operator that the calculated excavation reaction force has become greater than the preset upper limit value, or when the calculated excavation reaction force is greater than the preset upper limit value, the drive of the boom may be controlled so as to raise the boom and reduce the excavation depth.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to Patent Document 1, an overload state due to an excavation reaction force during an excavation operation can be appropriately determined, and the excavation operation can be corrected.

[0005] However, since Patent Document 1 focuses only on the magnitude of the excavation reaction force due to the excavation operation, depending on the direction of the excavation reaction force, even if the actuator's limit condition can be resolved by changing the posture of the boom or arm, it may be determined that the excavation reaction force is excessive, and a determination that the excavation operation needs to be corrected may be made.

[0006] For example, in a situation where the digging reaction force requires more than the maximum linear power that the arm cylinder can generate (hereinafter referred to as an overload state), depending on the posture of the boom and arm and the direction of movement of the boom and arm, the overload state of the arm may be resolved (the linear power of the arm cylinder decreases). In such cases, Patent Document 1 stops the digging operation and notifies the operator when the magnitude of the digging reaction force reaches a predetermined value, and the boom is raised manually or automatically. This results in interrupting the digging operation or correcting the trajectory of the digging operation, which reduces the digging efficiency.

[0007] The present invention has been made in view of the above, and its purpose is to provide a work machine that can perform excavation more efficiently by eliminating an overload condition caused by excavation reaction force during excavation operation by the boom and arm in the excavation control system of the work machine, without interrupting the excavation operation or correcting the trajectory of the excavation operation. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a work machine comprising: a vehicle body; a boom that rotates vertically relative to the vehicle body; an arm that rotates vertically relative to the boom; a boom cylinder connected to the vehicle body and the boom and driving the boom vertically relative to the vehicle body; an arm cylinder connected to the boom and the arm and driving the arm vertically relative to the boom; a first operating device that generates an operating signal to instruct the movement of the boom; a second operating device that generates an operating signal to instruct the movement of the arm; a first sensor that detects parameters relating to the linear force of the boom cylinder; a second sensor that detects parameters relating to the linear force of the arm cylinder; a third sensor that detects the posture of the boom; and a fourth sensor that detects the posture of the arm, wherein the operating signals of the first and second operating devices, the first sensor and the second The system further includes a controller that controls the driving of the boom cylinder and the arm cylinder based on the detection signals of the sensors, the detection signals of the third sensor and the fourth sensor, and in a combined operation in which the first operating device and the second operating device are operated simultaneously to drive the boom and the arm simultaneously, the controller calculates the linear power of the boom cylinder and the arm cylinder based on the detection signals of the first sensor and the second sensor, and if the linear power of either the boom cylinder or the arm cylinder reaches the limit value, the controller calculates the direction in which the linear power that has reached the limit value will decrease based on the detection signals of the third sensor and the fourth sensor and the linear power of the boom cylinder and the arm cylinder, and controls the driving of the boom cylinder and the arm cylinder so that the excavation operating point of the front work machine moves in the direction in which the linear power decreases.

[0009] In the present invention configured as described above, if the linear power of either the boom cylinder or the arm cylinder reaches a limit value, the direction in which the linear power that has reached the limit value decreases is calculated based on the detection signals of the third and fourth sensors and the respective linear powers of the boom cylinder and the arm cylinder. The drive of the boom cylinder and the arm cylinder is controlled so that the digging point of the front work implement moves in the direction in which the linear power decreases. As a result, even if the magnitude of the digging reaction force vector (magnitude of the digging vector) does not change, the load ratio of the linear power of the boom cylinder and the arm cylinder changes, and the linear power of the boom cylinder or the arm cylinder can be reduced. This makes it possible to resolve the overload condition caused by the digging reaction force during digging by the boom and arm without interrupting the digging operation or correcting the trajectory of the digging operation, allowing for more efficient digging and improved operability. [Effects of the Invention]

[0010] According to the present invention, when an overload condition occurs due to the excavation reaction force during excavation operation by the boom and arm, the overload condition can be resolved without interrupting the excavation operation or correcting the trajectory of the excavation operation, thereby enabling more efficient excavation operation. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of a hydraulic excavator to which the present invention is applied. [Figure 2] This figure shows the hydraulic circuit of a hydraulic drive device according to the first embodiment of the present invention. [Figure 3] This figure shows a control system according to a first embodiment of the present invention. [Figure 4] This diagram shows the direct force of the boom cylinder, the direct force of the arm cylinder, the boom angle, and the arm angle. [Figure 5] This is a flowchart explaining the functions of the controller's arithmetic control unit. [Figure 6] This is a diagram illustrating the distances J11 and J22 in equation (4). [Figure 7] It is a diagram showing the torque of each axis of the boom rotation fulcrum Pv1 and the arm rotation fulcrum Pv2 generated by the excavation reaction force vector FDig. [Figure 8] It is a diagram showing the torque of each axis of the boom rotation fulcrum Pv1 and the arm rotation fulcrum Pv2 generated by the boom linear motion force vector FBoom and the arm linear motion force vector FArm. [Figure 9] It is a diagram showing an example of a linear motion force reduction direction search map. [Figure 10] It is a diagram showing an example of a linear motion force reduction direction search map. [Figure 11] It is a diagram showing the form of intervention in the linear motion force reduction direction in the first embodiment of the present invention. [Figure 12] It is a diagram showing a simplified form of intervening in the linear motion force reduction direction with a hydraulic circuit. [Figure 13] It is a diagram showing a control system according to the second embodiment of the present invention. [Figure 14] It is a flowchart explaining the function of the arithmetic control unit of the controller. [Figure 15] It is a diagram showing the range (linear motion force reduction direction range) in which the cylinder linear motion force that has reached the limit value decreases, and the range 1 that coincides with the extension direction or the contraction direction of the boom cylinder and the range 2 that coincides with the extension direction or the contraction direction of the arm cylinder 3. [Figure 16] It is a diagram showing the hydraulic circuit of a hydraulic drive device according to the third embodiment of the present invention. [Figure 17] It is a diagram showing the pump control characteristics of the regulator. [Figure 18] It is a diagram showing a control system according to the third embodiment of the present invention. [Figure 19] It is a flowchart showing the details of the processing contents of the maximum possible pump discharge pressure calculation unit and the linear motion force limit value calculation unit of the controller. [Figure 20] It is an explanatory diagram of the calculation principle of the maximum dischargeable pressure in the maximum possible pump discharge pressure calculation unit. [Figure 21] It is a perspective view of a hydraulic excavator equipped with a control system according to the fourth embodiment of the present invention. [Figure 22] It is a diagram showing a control system according to a fourth embodiment of the present invention. [Figure 23] It is a flowchart showing a first display process of a control calculation unit of a controller. [Figure 24] It is a flowchart showing a second display process of a control calculation unit of a controller. [Figure 25] It is a diagram showing a change in an image displayed on a display device 70 by the first display process and the second display process. [Figure 26] It is a diagram showing an example of a range in the linear force decreasing direction.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a hydraulic excavator will be taken as an example of a working machine according to the present invention, and embodiments of the present invention will be described with reference to the drawings.

[0013] <First Embodiment> ~Working Machine~ FIG. 1 is a perspective view of a hydraulic excavator to which the present invention is applied.

[0014] The hydraulic excavator 100 comprises a lower traveling body 101, an upper rotating body 103 that is rotatably attached to the lower traveling body 101 via a slewing device 102 and constitutes the vehicle body, and a front working machine 104 that is attached to the front of the upper rotating body 103 and constitutes the working equipment. The front work implement 104 consists of a boom 105 mounted on the front of the upper slewing body 103 so as to be rotatable in the vertical direction, an arm 106 mounted on the tip of the boom 105 so as to be rotatable in the vertical direction, a bucket 107 mounted on the tip of the arm 106 so as to be rotatable in the vertical direction, a bucket link 108 mounted on the arm 106 and the bucket 107 so as to be rotatable, a boom cylinder 2 connected to the upper slewing body 103 and the boom 105, which changes the rotation angle between the upper slewing body 103 and the boom 105 by driving the boom 106 vertically relative to the upper slewing body 103, an arm cylinder 3 connected to the boom 105 and the arm 106, which changes the rotation angle between the boom 105 and the arm 106 by driving the arm 106 vertically relative to the boom 105, and a bucket cylinder 4 connected to the arm 106 and the bucket link 108, which changes the rotation angle between the arm 106 and the bucket 107 via the bucket link 108.

[0015] The lower traveling body 101 is equipped with crawler-type left and right traveling devices 109a and 109b (the right traveling device 109b is not shown), and the left and right traveling devices 109a and 109b are driven by left and right traveling motors 5a and 5b (the right traveling motor 5b is not shown), allowing the hydraulic excavator 100 to be moved to a desired position. The slewing device 102 is equipped with a slewing motor 6 that changes the rotation angle of the lower traveling body 101 and the upper slewing body 103.

[0016] The upper slewing body 103 is equipped with a cabin 110 that forms the operator's cab, and a controller 20 that performs the following control is located behind the operator's seat 111 inside the cabin 110. In addition, operating devices 21 and 22 are located on the left and right sides in front of the operator's seat 111 inside the cabin 110, which generate operation signals that instruct the operation (speed and direction) of the boom 105, arm 106, bucket 107, and upper slewing body 103 by the operator's operation, and operating devices 23a and 23b are located in front of the operator's seat 111, which generate operation signals that instruct the operation (speed and direction) of the left and right traveling devices 109a and 109b.

[0017] ~Hydraulic drive system~ Figure 2 shows the hydraulic circuit of the hydraulic drive device according to this embodiment. For the sake of simplicity, Figure 2 shows only the parts related to the boom cylinder 2 and arm cylinder 3 out of the boom cylinder 2, arm cylinder 3, bucket cylinder 4, left and right travel motors 5a and 5b, and swing motor 6.

[0018] In Figure 2, the hydraulic drive system of this embodiment includes a variable displacement hydraulic pump 10a (first hydraulic pump) and a hydraulic pump 10b (second hydraulic pump) driven by a prime mover (e.g., a diesel engine) not shown, an open center type flow control valve 11a (first flow control valve) connected to a center bypass passage 15a (first center bypass passage) connected to the discharge oil passage 13a of the hydraulic pump 10a, which controls the flow rate of pressurized oil supplied from the hydraulic pump 10a to the boom cylinder 2, an open center type flow control valve 12a (second flow control valve) connected in tandem to the center bypass passage 15a downstream of the flow control valve 11a, which controls the flow rate of pressurized oil supplied from the hydraulic pump 10a to the arm cylinder 3, and the discharge of the hydraulic pump 10b The system includes an open-center type flow control valve 12b (third flow control valve) connected to a center bypass passage 15b (second center bypass passage) connected to an oil outlet passage 13b, which controls the flow rate of pressurized oil supplied from the hydraulic pump 10b to the arm cylinder 3; an open-center type fourth flow control valve 11b (fourth flow control valve) connected in tandem to the center bypass passage 15b downstream of the flow control valve 12b, which controls the flow rate of pressurized oil supplied from the hydraulic pump 12b to the boom cylinder 2; a relief valve 14a connected to the discharge oil passage 13a of the hydraulic pump 10a, which limits the maximum value of the discharge pressure of the hydraulic pump 10a; and a relief valve 14b connected to the discharge oil passage 13b of the hydraulic pump 10b, which limits the maximum value of the discharge pressure of the hydraulic pump 10b.

[0019] The flow control valves 11a, 12a, 11b, and 12b are electromagnetically controlled spool valves, and the stroke (opening area) of the spool is controlled by a command signal from the controller 20.

[0020] Furthermore, the hydraulic drive system of this embodiment is configured as an open center system that connects the discharge oil passages 13a and 13b of the hydraulic pumps 10a and 10b to the tank T via center bypass passages 16a and 15b. In this open center system, when the flow control valves 11a, 12a, 11b, and 12b are in the neutral position shown in the figure, and the meter-in throttle and meter-out throttle of the flow control valves 11a, 12a, 11b, and 12b are fully closed, the flow control valves 11a, 12a, 11b, and 12b fully open the center bypass passages 15a and 15b, and return the discharge oil from the hydraulic pumps 10a and 10b to the tank T.

[0021] When the flow control valves 11a and 11b are operated from the neutral position shown in the figure to either the left or right position shown, the meter-in and meter-out throttles of the flow control valves 11a and 11b open, and the center bypass passages 15a and 15b are throttled, so that the discharge oil from the hydraulic pump 10a is supplied to the boom cylinder 2 via the flow control valve 11a and the actuator oil passage 16a or 16b, and the discharge oil from the hydraulic pump 10b is also supplied to the boom cylinder 2 via the flow control valve 11b and the actuator oil passage 16c or 16d. When the flow control valves 11a and 11b are half-operated, the meter-in and meter-out throttles of the flow control valves 11a and 11b open to an opening area corresponding to the amount of operation, and the center bypass passages 15a and 15b are narrowed to an opening area corresponding to the amount of operation. Pressurized oil at a flow rate corresponding to the amount of operation of the flow control valves 11a and 11b is then combined and supplied to the boom cylinder 2, and the boom cylinder 2 is driven at a speed corresponding to the amount of operation of the flow control valves 11a and 11b. When the flow control valves 11a and 11b are fully operated, the meter-in and meter-out throttles of the flow control valves 11a and 11b are fully open, and the center bypass passages 15a and 15b are fully closed. The entire amount of pressurized oil discharged from the hydraulic pumps 10a and 10b is supplied to the boom cylinder 2, and the boom cylinder 2 is driven at high speed.

[0022] The same applies when the flow control valves 12a and 12b are operated from the neutral position shown in the figure to either the left or right position shown in the figure. Discharge oil from the hydraulic pump 10b is supplied to the arm cylinder 3 via the flow control valve 12b and the actuator oil passage 17a or 17b, and discharge oil from the hydraulic pump 10a is supplied to the arm cylinder 3 via the actuator oil passage 17c or 17d. The arm cylinder 3 is driven by the pressurized oil discharged from the hydraulic pumps 10a and 10b at a speed corresponding to the amount the flow control valves 12a and 12b are operated.

[0023] When both flow control valves 11a, 11b and flow control valves 12a, 12b are half-operated to either the left or right position shown in the figure, the meter-in and meter-out throttles of flow control valves 11a, 11b and flow control valves 12a, 12b open to an opening area corresponding to the respective operating amounts, and the center bypass passages 15a, 15b are constricted. As a result, the discharged oil from hydraulic pump 10a is preferentially supplied to the upstream flow control valve 11a, and the remaining pressurized oil is supplied to flow control valve 12a. Similarly, the discharged oil from hydraulic pump 10b is preferentially supplied to the upstream flow control valve 12b, and the remaining pressurized oil is supplied to flow control valve 11b. Consequently, the pressurized oil discharged from hydraulic pumps 10a, 10b is combined and supplied to the boom cylinder 2 and arm cylinder 3, and the boom cylinder 2 and arm cylinder 3 are driven at speeds corresponding to the operating amounts of flow control valves 11a, 11b and flow control valves 12a, 12b.

[0024] Furthermore, when both flow control valves 11a, 11b and flow control valves 12a, 12b are fully operated to either the left or right position shown in the figure, the meter-in throttle and meter-out throttle of flow control valves 11a, 11b and flow control valves 12a, 12b are fully open, the center bypass passages 15a, 15b are fully closed, the entire amount of oil discharged from hydraulic pump 10a is supplied to the upstream flow control valve 11a, and the entire amount of oil discharged from hydraulic pump 10b is supplied to the upstream flow control valve 12b. As a result, the boom cylinder 2 is driven by the pressurized oil discharged from hydraulic pump 10a, and the arm cylinder 3 is driven by the pressurized oil discharged from hydraulic pump 10b.

[0025] ~Operating devices and sensors~ In Figure 1, the control device 21 functions as a boom control device (first control device) when the control lever is operated in the forward / backward direction, and as a bucket control device when the control lever is operated in the left / right direction. The control device 22 functions as a slewing control device when the control lever is operated in the forward / backward direction, and as an arm control device (second control device) when the control lever is operated in the left / right direction. Hereinafter, the control device 21 when functioning as a boom control device will be referred to as control device 21a (first control device), and the control device 22 when functioning as an arm control device will be referred to as control device 22a (second control device). The control device 21a generates control signals that instruct the movement of the boom 105 (target speed and direction), and the control device 22a generates control signals that instruct the movement of the arm 106 (target speed and direction).

[0026] Furthermore, operating devices 21, 22 and operating devices 23a, 23b are electrically operated devices that generate electrical operating signals, and the generated operating signals are transmitted to the controller 20.

[0027] In Figure 2, the actuator oil passage 16a connected to the bottom side of the boom cylinder 2 and the actuator oil passage 16b connected to the rod side are connected to pressure sensors 25a and 25b, respectively, which detect the pressure on the bottom side of the boom cylinder 2 and rod side, respectively. The actuator oil passage 17a connected to the bottom side of the arm cylinder 3 and the actuator oil passage 17b connected to the rod side are connected to pressure sensors 26a and 26b, respectively, which detect the pressure on the bottom side of the arm cylinder 3 and rod side, respectively. Pressure sensors 25a and 25b function as first sensors that detect parameters related to the linear force (described later) of the boom cylinder 2, and pressure sensors 26a and 26b function as second sensors that detect parameters related to the linear force (described later) of the arm cylinder 3.

[0028] As shown in Figure 1, the side of the boom 105 is equipped with an IMU 27 for detecting the rotation angle of the boom 105 relative to the upper slewing body 103, and the side of the arm 106 is equipped with an IMU 28 for detecting the rotation angle of the arm 106 relative to the boom 105. The IMU 27 functions as a third sensor for detecting the attitude of the boom 105, and the IMU 28 functions as a fourth sensor for detecting the attitude of the arm 106.

[0029] IMU27 and 28 consist of known inertial measurement units.

[0030] ~ Control System ~ Figure 3 shows the control system according to this embodiment.

[0031] In Figure 3, the operation signals from operating device 21, including operating device 21a (first operating device), and operating device 22, including operating device 22a (second operating device), the detection signals from pressure sensors 25a, 25b and pressure sensors 26a, 26b, and the detection signals from IMUs 27, 28 are input to the controller 20. The controller 20 performs predetermined calculations and outputs command signals to a plurality of flow control valves, including flow control valves 11a, 12a, 11b, and 12b.

[0032] When operating devices 21a (first operating device) and 22a (second operating device) are operated simultaneously to perform a combined operation that drives the boom 105 and arm 106 simultaneously, the controller 20 calculates the linear force of the boom cylinder 2 and arm cylinder 3 based on the detection signals of pressure sensors 25a, 25b (first sensors) and pressure sensors 26a, 26b (second sensors). If the linear force of either the boom cylinder 2 or arm cylinder 3 has not reached its limit, the controller 20 operates the boom cylinder 2 based on the operating signals of the operating devices 21a and 22a. The system drives cylinder 2 and arm cylinder 3. If the linear force of either boom cylinder 2 or arm cylinder 3 reaches a limit value, the system calculates the direction in which the linear force that has reached the limit value will decrease based on the detection signals from IMU 27 (third sensor) and IMU 28 (fourth sensor) and the respective linear forces of boom cylinder 2 and arm cylinder 3. The system then controls the driving of boom cylinder 2 and arm cylinder 3 so that the tip of the bucket 107, which is the digging operating point Pw (see Figure 4) of the front work implement 104, moves in the direction in which the linear force decreases.

[0033] The functions of controller 20 are described in detail below.

[0034] As shown in Figure 3, the controller 20 has multiple functional elements, including a linear power calculation unit 20a, a posture calculation unit 20b, a storage unit 20c, and a control calculation unit 20d.

[0035] The linear power calculation unit 20a calculates the linear power of the boom cylinder 2 and the linear power of the arm cylinder 3 based on the detection signals from the pressure sensors 25a and 25b (first sensors) and the detection signals from the pressure sensors 26a and 26b (second sensors).

[0036] Figure 4 shows the direct power of the boom cylinder 2 and the direct power of the arm cylinder 3, as well as the boom angle and arm angle, which will be described later.

[0037] In Figure 4, the symbol Fb represents the direct force of the boom cylinder 2, and the symbol Fa represents the direct force of the arm cylinder 3. The direct force Fb of the boom cylinder 2 represents the axial thrust (driving force) acting on the piston rod of the boom cylinder 2, and the direct force Fa of the arm cylinder 3 represents the axial thrust (driving force) acting on the piston rod of the arm cylinder 3.

[0038] The linear force calculation unit 20a calculates the linear force Fa of the boom cylinder 2 by subtracting the thrust obtained by multiplying the piston pressure receiving area on the rod side of the boom cylinder 2 by the pressure detected by the pressure sensor 25a from the thrust obtained by multiplying the piston pressure receiving area on the bottom side of the boom cylinder 2 by the pressure detected by the pressure sensor 25a. Similarly, the linear force calculation unit 20a calculates the linear force Fa of the arm cylinder 3 by subtracting the thrust obtained by multiplying the piston pressure receiving area on the rod side of the arm cylinder 3 by the pressure detected by the pressure sensor 26b from the thrust obtained by multiplying the piston pressure receiving area on the bottom side of the arm cylinder 3 by the pressure detected by the pressure sensor 26a.

[0039] In the following, the direct force Fb of the boom cylinder 2 may simply be referred to as the boom direct force, and the direct force Fa of the arm cylinder 3 may simply be referred to as the arm direct force.

[0040] In Figure 4, the symbol FBoom represents the linear power vector of boom cylinder 2, which is the linear power Fb of boom cylinder 2 plus the directional component of the linear power Fb. The symbol FArm represents the linear power vector of arm cylinder 3, which is the linear power Fa of arm cylinder 3 plus the directional component of the linear power Fa. Also in Figure 4, the excavation reaction force vector is shown with the symbol FDig.

[0041] The attitude calculation unit 20b calculates the rotation angle (boom angle) θ1 of the boom 105 relative to the upper slewing body 103 and the rotation angle (arm angle) θ2 of the arm 106 relative to the boom 105 based on the detection signals from IMU 27 (third sensor) and IMU 28 (fourth sensor).

[0042] In Figure 4, the boom angle θ1 (the rotation angle of the boom 105 relative to the upper slewing body 103) is the angle formed by the line segment BL passing through the pivot point (pin) Pv1 of the boom 105 and the pivot point (pin) Pv2 of the arm 106, with respect to the line segment SL in the front-rear direction parallel to the bottom plate (slewing frame) 103a of the upper slewing body 103, which passes through the pivot point (pin) Pv1 of the boom 105. The arm angle θ2 (the rotation angle of the arm 106 relative to the boom 105) is the angle formed by the line segment AL passing through the pivot point (pin) Pv2 of the arm 106 and the pivot point (pin) Pv3 of the bucket 107, with respect to the line segment BL.

[0043] The memory unit 20c stores various data used in calculations by the control calculation unit 20d. In this embodiment, it stores limit values ​​for the boom linear power Fb and the arm linear power Fa, and a search map (hereinafter sometimes referred to as the linear power reduction direction search map) that searches for the direction in which the linear power decreases once the limit value is reached.

[0044] The limit value of the direct force may be a predetermined value, or it may be a value calculated based on the operating information at that time. In this embodiment, the limit value of the direct force is a predetermined value. The predetermined value is, for example, the direct force calculated based on the maximum discharge pressure of the hydraulic pumps 10a and 10b limited by the relief valves 14a and 14b. The direct force reduction direction search map will be described later.

[0045] Figure 5 is a flowchart illustrating the functions of the control calculation unit 20d.

[0046] First, the control calculation unit 20d determines whether a combined operation is being performed to simultaneously drive the boom 105 and the arm 106 based on the operation signals from the operating devices 21a and 22a (step S100). If the combined operation is not being performed, the control calculation unit 20d calculates a control command for the flow control valve so that the corresponding actuator is driven according to the operation signal from the operating device 21a or 22a, and outputs the command signal to the flow control valve (step S150). At this time, the boom 105 or the arm 106 is driven according to the operation signal from the operating device 21a or 22a.

[0047] If the determination in step S100 indicates that a combined operation is being performed, the control calculation unit 20d further compares the linear powers Fb and Fa of the boom cylinder 2 and arm cylinder 3 calculated by the linear power calculation unit 20a with the limit values ​​of the linear power stored in the storage unit 20c, and determines whether either of the linear powers Fb or Fa has reached the limit value of the linear power (step S110). If the determination in step S110 indicates that neither of the linear powers has reached the limit value, the control calculation unit 20d calculates control commands for the flow control valves 11a, 11b, 12a, and 12b so that the boom cylinder 2 and arm cylinder 3 are driven according to the operation signals of the operating devices 21a and 22a, and outputs the command signals to the flow control valves 11a, 11b, 12a, and 12b (step S150). At this time, the boom 105 and arm 106 are driven according to the operation signals of the operating devices 21a and 22a.

[0048] On the other hand, if the determination in step S110 indicates that the linear force Fb or Fa of either the boom cylinder 2 or the arm cylinder 3 has reached the limit value of the linear force, the control calculation unit 20d calculates the magnitude and direction of the digging reaction force vector FDig, which indicates the magnitude and direction of the digging reaction force acting on the digging operating point Pw (the tip of the bucket 107) of the front work implement 104, according to equation (1), based on the linear forces Fb and Fa of the boom cylinder 2 and the arm cylinder 3 calculated by the linear force calculation unit 20a, and the boom angle θ1 (the posture of the boom 105) and arm angle θ2 (the posture of the arm 106) calculated by the posture calculation unit 20b (step S120).

[0049]

number

[0050] Let's explain equation (1).

[0051] In equation (1), J 1, The T in the upper right corner of J2 represents the transpose matrix. The same applies to the T in the upper right corner of the following matrices. Also, the values ​​of each variable are as follows:

[0052] FDig: Excavation reaction vector as described above FCylinder: This is the cylinder's direct power vector, which is the sum of the direct power vector FBoom of the boom cylinder 2 and the direct power vector FArm of the arm cylinder 3 described above. The cylinder's direct power vector is expressed by the following equation (2).

[0053]

number

[0054] J1 is the Jacobian matrix represented by the following equation (3), with boom angle θ1, arm angle θ2, boom length L1, and arm length L2 as its elements.

[0055]

number

[0056] As shown in Figure 7, which will be described later, the boom length L1 is the distance between the boom pivot point (pin) Pv1 and the arm pivot point (pin) Pv2, and the arm length L2 is the distance between the arm pivot point (pin) Pv2 and the bucket pivot point (pin) Pv3.

[0057] J2 is a Jacobian matrix represented by the following equation (4), whose elements are the distance J11 from the boom pivot point (pin) Pv1 to the central axis of the boom cylinder 2, and the distance J22 from the arm pivot point (pin) Pv2 to the central axis of the arm cylinder 3.

[0058]

number

[0059] Figure 6 illustrates the distances j11 and j22 in equation (4). j11 is the length of the perpendicular line drawn from the boom pivot point (pin) Pv1 to the central axis of the boom cylinder 2, and can be calculated from the geometric relationship between the boom angle θ1, the distance Cp1 between the boom pivot point Pv1 and the pivot point Pv3 at the base end of the boom cylinder 2, and the distance Cm1 between the boom pivot point Pv1 and the pivot point Pv4 at the tip of the rod of the boom cylinder 2. j22 is the length of the perpendicular line drawn from the arm pivot point (pin) Pv2 to the central axis on the arm cylinder 3, and can be calculated from the geometric relationship between the arm angle θ2, the distance Cp2 between the arm pivot point Pv2 and the pivot point Pv5 at the base end of the arm cylinder 3, and the distance Cm2 between the arm pivot point Pv2 and the pivot point Pv6 at the tip of the rod of the arm cylinder 3.

[0060] Let's explain the derivation process of equation (1).

[0061] Equation (1) is derived from the balance between the torques on each axis of the boom pivot point Pv1 and the arm pivot point Pv2, which are generated by the excavation reaction force vector FDig, and the torques on each axis of the boom pivot point Pv1 and the arm pivot point Pv2, which are generated by the linear power vector FBoom of the boom cylinder 2 (hereinafter sometimes referred to as the boom linear power vector) and the linear power vector FArm of the arm cylinder 3 (hereinafter sometimes referred to as the arm linear power vector).

[0062] Figure 7 shows the torques on each axis of the boom pivot point Pv1 and the arm pivot point Pv2, which are generated by the excavation reaction force vector FDig.

[0063] Figure 8 shows the torques on each axis of the boom pivot point Pv1 and the arm pivot point Pv2, generated by the boom linear power vector FBoom and the arm linear power vector FArm.

[0064] In Figures 7 and 8, the torques on each axis of the boom pivot point Pv1 and the arm pivot point Pv2 are indicated by the signs τ1 and τ2.

[0065] The relationship between the drilling vector that generates the drilling reaction force vector FDig and the torques τ1 and τ2 is expressed by equation (5) below.

[0066]

number

[0067]

number

[0068]

number

[0069] From equations (5), (6A), and (6B), the following relationship can be obtained.

[0070]

number

[0071]

number

[0072] Returning to Figure 5, the control calculation unit 20d calculates the direction in which the cylinder direct force Fb or Fa decreases when it reaches a limit value, based on the excavation reaction force vector FDig, boom angle θ1, arm angle θ2 (attitude), the direct force Fb of the boom cylinder 2, and the direct force Fa of the arm cylinder 3 (step S130).

[0073] More specifically, when the linear force of either the boom cylinder 2 or the arm cylinder 3 reaches a limit value, the control calculation unit 20d calculates the digging reaction force vector FDig acting on the digging operating point Pw (the tip of the bucket 107) of the front work implement 104 based on the detection signals from IMU 27 (third sensor) and IMU 28 (fourth sensor) and the linear forces of the boom cylinder 2 and the arm cylinder 3. Based on this digging reaction force vector FDig and the detection signals from IMU 27 (third sensor) and IMU 28 (fourth sensor) and the linear forces of the boom cylinder 2 and the arm cylinder 3, it calculates the direction in which the linear force of the hydraulic cylinder that has reached the limit value decreases while maintaining the magnitude of the digging reaction force vector FDig.

[0074] Next, the control calculation unit 20d calculates a control command to operate the boom cylinder 2 and arm cylinder 3 so that the digging operating point Pw (the tip of the bucket 107) of the front work implement 104 moves in the direction that reduces the linear power of the hydraulic cylinder that has reached its limit, as calculated in step S130, and outputs the command signal to the flow control valves 11a, 11b, 12a, and 12b (step S140). As a result, the boom cylinder 2 and arm cylinder 3 are controlled so that the digging operating point (the tip of the bucket 107) of the front work implement 104 moves in the direction that reduces the linear power calculated in step S103.

[0075] Step S130 describes the calculation method for determining the direction in which the linear power of a hydraulic cylinder decreases when it reaches its limit (hereinafter sometimes simply referred to as the direction of linear power decrease).

[0076] Examples of calculation methods for the direction of decrease in linear force include the following:

[0077] (a) A method to obtain the Jacobian matrices J1 and J2 in the vicinity of the current orientation of the front work machine 104 (see Figure 1) (hereinafter sometimes simply referred to as the front orientation), and to obtain them online by iteratively calculating the linear power vector FCylinder; (b) A method that involves pre-calculating Jacobian matrices J1 and J2 for all front positions within the operating range of the hydraulic cylinder, creating a map for each front position, and then using these maps to determine the result; (c) A method that uses the front attitude, excavation reaction vector FDig, and linear power vector FCylinder as a set to create multiple maps (linear power reduction direction search maps) with different front attitudes, excavation reaction vector FDig, and linear power vector FCylinder (boom linear power, arm linear power), and then uses these maps to determine the result.

[0078] The calculation method for step S130 can be any method other than the one described above, as long as it is possible to determine the direction in which the cylinder's direct force decreases from the current front posture.

[0079] Figures 9 and 10 show an example of a linear power reduction direction search map used in the calculation method described in (c) above.

[0080] The direct force reduction direction search map shows the magnitude of the arm direct force, which is part of the direct force vector FCylinder, for a given excavation reaction force vector FDig, using grayscale (contour lines). Figures 9 and 10 show straight lines on the map representing the boom and arm as the front posture. The grayscale represents a set of unit sections where position information and arm direct force magnitude information are stored. For example, position information is stored as values ​​in the XY coordinate system, and the arm direct force magnitude is stored as a numerical value (scalar value).

[0081] Figures 9 and 10 show maps of the arm's direct force, but there is also a separate map of the boom's direct force. Furthermore, Figures 9 and 10 are examples for a given excavation reaction force vector, and there are maps with different shades of black and white indicating the magnitude of the direct force for each excavation reaction force vector.

[0082] The control calculation unit 20d, for example, when the arm linear power reaches its limit, selects a map that sets the front posture, excavation reaction force vector, and arm linear power at that time, and, using the current position of the excavation operating point Pw of the front work implement 104 as a reference, selects, for example, the unit section in which the arm linear power decreases the most among the unit sections in which the arm linear power decreases when it reaches its limit, selects the direction in which that unit section is located as the direction of linear power decrease, and changes the front posture so that the excavation operating point Pw moves in that direction.

[0083] In Figures 9 and 10, symbol A indicates the position of the drilling start point Pw when the arm's linear power reaches its limit and the direction of linear power reduction is searched, and symbol B indicates the position of the drilling start point Pw after the direction of linear power reduction has been selected and the front attitude has been changed. When searching for the direction of linear power reduction, the front attitude is as shown in Figure 9, and when the front attitude is changed so that the drilling start point Pw moves in the direction of linear power reduction, the drilling start point Pw moves from position A to position B, as shown in Figure 10.

[0084] By changing the front posture in this way, even if the magnitude of the excavation reaction force vector (magnitude of the excavation vector) does not change, the ratio of the linear power load on the boom cylinder 2 and the arm cylinder 3 changes, and the linear power of the arm cylinder 3, which has reached its limit, can be reduced.

[0085] In step S140, the control calculation unit 20d calculates a control command to move the excavation operating point Pw of the front work implement 104 from position A to position B based on the position information of position A and position B, and outputs a command signal.

[0086] The method for calculating the control command in step S140 will be explained.

[0087] In step S140, in order to move the digging start point Pw of the front work implement 104 from position A to position B, the operation signals of the control devices 21a and 22a input to the controller 20 should be corrected so that the digging start point Pw moves in a direction in which the linear power calculated in step S130 decreases.

[0088] In this embodiment, the controller 20 corrects the operation signals of the operating devices 21a and 22a by intervening with the direction of linear power reduction calculated in step S130, and then generates a command signal. However, the form of intervention is not limited to this, as long as the direction of linear power reduction calculated in step S130 can be intervened in the operation signals of the operating devices 21a and 22a.

[0089] Figure 11 is a diagram showing the form of intervention in the direction of linear force reduction in this embodiment. Figure 11 shows a simplified version of the hydraulic drive system shown in Figure 2. As described above, the operation signals from the operating devices 21a and 22a are input to the controller 20, which corrects the operation signals by intervening with the linear force reduction direction calculated in step S130 and generates a command signal. This command signal is output directly to the solenoids 11S of the flow control valves 11a, 11b, 12a, and 12b of the hydraulic drive system.

[0090] Figure 12 is a simplified diagram showing how the linear force reduction direction calculated in step S130 is intervened in the hydraulic circuit.

[0091] In Figure 12, the flow control valve 11 is a hydraulic pilot-operated switching valve equipped with a hydraulic drive unit 11h to which a signal pressure is derived from a hydraulic pilot circuit 66. The hydraulic pilot circuit 66 is switched by lever operation of operating devices 21a and 22a and includes an operating pressure reducing valve 60 that generates the operating pilot pressure in normal mode, a pilot pump 61 and a pilot relief valve 62 that constitute the pilot hydraulic power source 67, a solenoid pressure reducing valve 63 that generates the control pilot pressure in intervention mode based on a command signal from the controller 20, and a solenoid switching valve 64 that switches the signal pressure led to the hydraulic drive unit 11h between the operating pilot pressure in normal mode and the control pilot pressure in intervention mode.

[0092] If neither the boom direct power nor the arm direct power has reached its limit, the controller 20 is in normal mode, and the solenoid pressure reducing valve 63 and the solenoid switching valve 64 are in the positions shown in the diagram.

[0093] In this normal mode, the operating pilot pressure generated by the operating devices 21a and 22a is guided via the solenoid switching valve 64 to the hydraulic drive unit 11h of the flow control valve 11, and the boom cylinder 2 and arm cylinder 3 are driven in response to the lever operation of the operating devices 21a and 22a.

[0094] When either the boom direct force or the arm direct force reaches its limit, the controller 20 switches from normal mode to intervention mode. In this intervention mode, the controller 20 calculates control commands to operate the boom cylinder 2 and the arm cylinder 3 in a direction that reduces the cylinder direct force, and outputs command signals to the solenoid pressure reducing valve 63 and the solenoid switching valve 64, respectively.

[0095] The solenoid pressure reducing valve 63 generates a control pilot pressure for the intervention mode in response to a command signal from the controller, and the solenoid switching valve 64 switches from the position shown in the diagram in response to the command signal from the controller.

[0096] As a result, the control pilot pressure of the intervention mode generated by the solenoid pressure reducing valve 63 is guided via the solenoid switching valve 64 to the hydraulic drive unit 11h of the flow control valve 11, and the boom cylinder 2 and arm cylinder 3 are controlled so that the digging operating point of the front work implement 104 (the tip of the bucket 107) moves in a direction that reduces the direct force of the arm cylinder 3.

[0097] ~Effects~ According to this embodiment, when the linear power of either the boom cylinder 2 or the arm cylinder 3 reaches its limit, the system calculates the direction in which the linear power of either the boom cylinder 2 or the arm cylinder 3 will decrease according to the posture of the boom 105 and the arm 106, and controls the driving of the boom cylinder 2 and the arm cylinder 3 so that the digging operating point Pw (bucket tip) of the front work implement 104 moves in that direction. As a result, even if the magnitude of the digging reaction force vector (magnitude of the digging vector) does not change, the load ratio of the linear power of the boom cylinder 2 and the arm cylinder 3 changes, and the linear power of the boom cylinder 2 or the arm cylinder 3 that has reached its limit can be reduced. This makes it possible to resolve the overload condition caused by the digging reaction force during digging by the boom 105 and the arm 106 without interrupting the digging operation or making discontinuous trajectory corrections to the digging operation, thereby enabling more efficient digging and improving operability.

[0098] In this embodiment, the controller 20 is located on the upper rotating body 103, but the controller 20 may be located anywhere as long as it is possible to issue operation commands to the actuator.

[0099] Furthermore, although this embodiment uses a three-link configuration consisting of a boom 105, arm 106, and bucket 107, the number of links and their shape can be anything as long as the mechanism has two or more links with a working device at its tip. Also, "boom" and "arm" are names for the links, and other names may be used for links that have equivalent functions.

[0100] Furthermore, in this embodiment, a pressure sensor was used to calculate the linear force of the hydraulic cylinder, but any type of sensor is acceptable as long as it can measure the linear force of the hydraulic cylinder. For example, a strain gauge or piezoelectric element may be embedded in the piston rod along with a strain generating element.

[0101] Furthermore, in this embodiment, IMUs 27 and 28 were used as sensors to detect the posture of the boom 105 and arm 106. However, instead of IMUs 27 and 28, angle sensors may be provided on the rotary joints of the boom 105 and arm 106, and the posture of the boom cylinder 2 and arm cylinder 3 may be measured using the angle sensors.

[0102] <Second Embodiment> A second embodiment of the present invention will now be described.

[0103] Figure 13 shows the control system according to this embodiment.

[0104] In this embodiment, the controller 20 of the control system further includes the functional elements of the lever operation direction determination unit 20e, in addition to the functional elements of the controller 20 of the first embodiment shown in Figure 3.

[0105] The controller 20, in the lever operation direction determination unit 20e, determines whether the lever operation direction of the operating device 21a (first operating device) and operating device 22a (second operating device) is the extension direction or the retraction direction of the boom cylinder 2 and arm cylinder 3, respectively, based on the operation signals from the operating device 21a (first operating device) and operating device 22a (second operating device), and sends the determination result to the control calculation unit 20d.

[0106] The control calculation unit 20d determines whether there is a range within the direction in which the linear power that has reached its limit decreases that coincides with the extension or retraction direction of the boom cylinder 2 and the arm cylinder 3. If a matching range exists, it calculates the direction in which the linear power that has reached its limit decreases within that matching range and controls the driving of the boom cylinder 2 and the arm cylinder 3 so that the digging operating point Pw of the front work implement 104 moves in that direction. If a matching range does not exist, it stops the driving of the boom cylinder 2 and the arm cylinder 3.

[0107] Figure 14 is a flowchart illustrating the functions of the control calculation unit 20d.

[0108] After steps S100 to S120, the control calculation unit 20d, for example, using the linear power reduction direction search map selected in the control calculation unit 20d, calculates in step S130A the range in which the cylinder linear power Fb or Fa decreases when it reaches its limit value (hereinafter sometimes referred to as the linear power reduction direction range) based on the excavation reaction force vector FDig, boom angle θ1, arm angle θ2 (attitude), the linear power Fb of the boom cylinder 2, and the linear power Fa of the arm cylinder 3 (step S130A).

[0109] Figure 26 shows an example of the linear power reduction direction range. The linear power reduction direction range is a predetermined area in which the linear power of a unit section decreases, calculated based on the current position of the drilling operation point Pw in the linear power reduction direction search map selected by the control calculation unit 20d. The size and shape of the predetermined range may be predetermined, or it may be calculated as a range that includes the value obtained by multiplying the movement speed of the drilling operation point Pw by the calculation step time of the controller (the distance to the next step).

[0110] Next, the control calculation unit 20d determines whether there is a range 1 (see Figure 15) that matches the extension or retraction direction of the boom cylinder 2 obtained from the lever operation direction determination unit 20e, or a range 2 (see Figure 15) that matches the extension or retraction direction of the arm cylinder 3, within the range of linear power reduction (S132). If neither range 1 nor range 2 exists within the range of linear power reduction, the control calculation unit 20d stops the boom cylinder 2 and the arm cylinder 3 (S140D). If either range 1 or range 2 exists within the range of the direction of linear power reduction, the control calculation unit 20d further determines whether either range 1 or range 2 exists within the range of the direction of linear power reduction (S134). If either range 1 or range 2 exists within the range of the direction of linear power reduction, the control calculation unit 20d calculates the direction in which the linear power decreases within the range of range 1 or range 2 that exists within the range of the direction of linear power reduction, calculates a control command to operate the boom cylinder 2 and arm cylinder 3 so that the digging operating point Pw (the tip of the bucket 107) of the front work implement 104 moves in that direction, and operates the boom cylinder 2 and arm cylinder 3 (S140A).

[0111] Next, if both range 1 and range 2 exist within the range of the direction of linear power reduction and overlap (S136), the control calculation unit 20d calculates the direction in which the linear power decreases within the overlapping range of range 1 and range 2, calculates a control command to operate the boom cylinder 2 and arm cylinder 3 so that the digging operating point Pw (the tip of the bucket 107) of the front work implement 104 moves in that direction, and operates the boom cylinder 2 and arm cylinder 3 (S140B).

[0112] In step S136, if range 1 and range 2 do not overlap, the control calculation unit 20d selects one of range 1 and range 2 from a predetermined range, calculates the direction in which the linear power decreases within that range, calculates a control command to operate the boom cylinder 2 and arm cylinder 3 so that the digging operating point Pw (the tip of the bucket 107) of the front work implement 104 moves in that direction, and operates the boom cylinder 2 and arm cylinder 3 (S140C).

[0113] Figure 15 shows the range in which the cylinder's direct force Fb or Fa decreases when it reaches its limit (direct force decrease range), range 1 which coincides with the extension or retraction direction of the boom cylinder 2, and range 2 which coincides with the extension or retraction direction of the arm cylinder 3.

[0114] The range of the direction of linear power reduction for boom cylinder 2 and arm cylinder 3 is, as described above, a range calculated using, for example, a linear power reduction direction search map selected by the control calculation unit 20d (step S130A in Figure 14), and this range is shown by diagonal lines in Figure 15.

[0115] In Figure 15, range 1, which coincides with the extension direction of the boom cylinder 2, is formed on the side of the pivot point Pv2 of the arm 106 on the movement trajectory Ta of the excavation operating point Pw when the arm 106 is rotated by the arm cylinder 3. Range 1, which coincides with the retraction direction of the boom cylinder 2, is formed on the opposite side of the pivot point Pv2 of the arm 106 on the movement trajectory Ta, and on the side of the pivot point Pv1 of the boom 105 on the movement trajectory Tb of the excavation operating point Pw when the boom 105 is rotated by the boom cylinder 2. Range 2, which coincides with the extension direction of the arm cylinder 3, is formed on the side of the pivot point Pv1 on the movement trajectory Tb. Range 2, which coincides with the extension direction of the arm cylinder 3, is formed on the side of the pivot point Pv1 of the movement trajectory Ta, and on the opposite side of the pivot point Pv2 of the movement trajectory Ta, and on the opposite side of the pivot point Pv1 of the movement trajectory Ta.

[0116] ~Effects~ According to this embodiment, when the extension and retraction direction of at least one of the boom cylinder 2 and the arm cylinder 3 coincides with the extension and retraction direction indicated by the operation signals of the operating devices 21a and 22a, the digging operating point Pw (bucket tip) of the front work implement 104 is controlled to move in a direction that reduces the linear power of the boom cylinder 2 or the arm cylinder 3, calculated according to the posture of the boom 105 and the arm 106. In addition to the effects of the first embodiment, this embodiment allows for operation that better reflects the operator's actions and further improves operability.

[0117] <Third Embodiment> A third embodiment of the present invention will now be described.

[0118] Figure 16 shows the hydraulic circuit of the hydraulic drive device according to this embodiment. The hydraulic drive device shown in Figure 16, like the hydraulic drive device shown in Figure 2, includes a variable displacement hydraulic pump 10a (first hydraulic pump) and a hydraulic pump 10b (second hydraulic pump), an open-center type flow control valve 11a (first flow control valve), an open-center type flow control valve 12a (second flow control valve), an open-center type flow control valve 12b (third flow control valve), an open-center type fourth flow control valve 11b (fourth flow control valve), and relief valves 14a and 14b.

[0119] Furthermore, the hydraulic drive device according to this embodiment further includes a regulator 56a that controls the discharge flow rate of the hydraulic pump 10a so that the absorption horsepower of the hydraulic pump 10a does not exceed a preset maximum horsepower, a regulator 56b that controls the discharge flow rate of the hydraulic pump 10b so that the absorption horsepower of the hydraulic pump 10b does not exceed a preset maximum horsepower, a pressure sensor 58a (fifth sensor) that detects the intermediate pressure of the pressurized oil flowing through the first center bypass passage 15a between the first flow control valve 11a and the second flow control valve 12a, a pressure sensor 58b (sixth sensor) that detects the intermediate pressure of the pressurized oil flowing through the second center bypass passage 15b between the third flow control valve 12b and the fourth flow control valve 11b, a pressure sensor 57a (seventh sensor) connected to the discharge oil passage 13a of the hydraulic pump 10a and detecting the discharge pressure of the hydraulic pump 10a, and a pressure sensor 57a (eighth sensor) connected to the discharge oil passage 13b of the hydraulic pump 10b and detecting the discharge pressure of the hydraulic pump 10b.

[0120] Figure 17 shows the pump control characteristics of regulators 56a and 56b.

[0121] In Figure 17, Pmin is the minimum discharge pressure of hydraulic pumps 10a and 10b when all operating devices are not operated; Pmax is the maximum discharge pressure of hydraulic pumps 10a and 10b determined by the set pressure of relief valves 14a and 14b; qmax is the maximum capacity (maximum tilt angle) determined by the structure of hydraulic pumps 10a and 10b; and Qmax is the maximum flow rate of hydraulic pumps 10a and 10b obtained by multiplying qmax by the pump rotation speed. In Figure 17, Qmax is shown assuming that the pump rotation speed is constant.

[0122] When the discharge pressure of hydraulic pumps 10a and 10b is between the minimum pressure Pmin and the pressure Pa, the maximum capacity of hydraulic pumps 10a and 10b is qmax. When the discharge pressure of hydraulic pumps 10a and 10b is between the minimum pressure Pa and the maximum pressure Pmax, the maximum capacity of hydraulic pumps 10a and 10b is limited by the torque characteristic curve CTmax) where "pump discharge pressure × capacity = constant". As the discharge pressure of hydraulic pumps 10a and 10b increases, the capacity of hydraulic pumps 10a and 10b decreases, and the capacity of hydraulic pumps 10a and 10b is controlled so that the absorbed torque of hydraulic pumps 10a and 10b does not exceed the maximum torque Tmax (constant torque control).

[0123] Furthermore, as the capacity and torque of the hydraulic pumps 10a and 10b are controlled as described above, the discharge flow rate and absorbed horsepower of the hydraulic pumps 10a and 10b are controlled in the same way. That is, when the discharge pressure of the hydraulic pumps 10a and 10b is between the minimum pressure Pmin and the pressure Pa, the maximum flow rate of the hydraulic pumps 10a and 10b is Qmax. When the discharge pressure of the hydraulic pumps 10a and 10b is between the minimum pressure Pa and the maximum pressure Pmax, the maximum flow rate of the hydraulic pumps 10a and 10b is limited to the horsepower characteristic curve CHmax) where "pump discharge pressure × flow rate = constant". As the discharge pressure of the hydraulic pumps 10a and 10b increases, the discharge flow rate of the hydraulic pumps 10a and 10b decreases, and the discharge flow rate of the hydraulic pumps 10a and 10b is controlled so that the absorbed horsepower of the hydraulic pumps 10a and 10b does not exceed the maximum horsepower Hmax (constant horsepower control).

[0124] Figure 18 shows the control system according to this embodiment.

[0125] In Figure 18, the controller 20, as shown in Figure 18, further includes the functional elements of the controller 20 of the first embodiment shown in Figure 3, as well as the functional elements of a maximum possible pump discharge pressure calculation unit 20f and a direct power limit value calculation unit 20g. The storage unit 20c stores the pump control characteristics, including the setting of the maximum horsepower Hmax used in controlling the regulators 56a and 56b, instead of the direct power limit values ​​(limit values ​​for boom direct power Fb and arm direct power Fa) that were stored in the storage unit 20c of the controller 20 of the first embodiment.

[0126] Furthermore, in addition to the input signals of the controller 20 in the first embodiment shown in Figure 3 (operation signals of the operating devices 21a and 22a, detection signals of pressure sensors 25a and 25b and pressure sensors 26a and 26b, and detection signals of IMUs 27 and 28), the controller 20 also receives the detection signals of the pressure sensors 58a and 58b mentioned above. Based on these input signals, the controller 20 performs the following calculations in addition to the calculations of the controller 20 in the first embodiment shown in Figure 3, and outputs command signals to a plurality of flow control valves, including flow control valves 11a, 12a, 11b, and 12b, and regulators 56a and 56b.

[0127] First, the controller 20, in its control calculation unit 20d, calculates a command value to control the discharge flow rate of the hydraulic pump 10a so that the absorption horsepower of the hydraulic pumps 10a and 10b does not exceed the maximum horsepower, based on the detection signals from the pressure sensors 57a and 57b and the maximum horsepower Hmax of the pump control characteristics stored in the memory unit 20c, and outputs a command signal to the regulators 56a and 56b. Based on this command signal, the regulators 56a and 56b perform the torque / horsepower constant control described above.

[0128] Furthermore, the control of regulators 56a and 56b may not be electronic control based on command signals output from the controller 20, but rather hydraulic control that guides the discharge pressure of hydraulic pumps 10a and 10b to regulators 56a and 56b to drive the capacity changing members (e.g., swash plates) of hydraulic pumps 10a and 10b.

[0129] Furthermore, the controller 20 calculates the maximum possible discharge pressure of hydraulic pumps 10a and 10b, limited by the maximum horsepower Hmax, based on the operation signals of the operating devices 21a and 22a, the detection signals of the pressure sensors 58a and 58b, and the maximum horsepower Hmax of the pump control characteristics, assuming that the direct force of either the boom cylinder 2 or the arm cylinder 3 is in an overload state where it has reached its limit value. The direct force limit value calculation unit 20g calculates the maximum possible direct force of the boom cylinder 2 or the arm cylinder 3 when the drive of the boom cylinder 2 or the arm cylinder 3 is stopped and the pressure on the discharge side of the boom cylinder 2 or the arm cylinder 3 is 0, by multiplying the pressure receiving area of ​​the pistons of the boom cylinder 2 and the arm cylinder 3 by the maximum possible discharge pressure. The control calculation unit 20d uses this maximum possible direct force as the limit value of the direct force and calculates the direction in which the direct force of the hydraulic cylinder that has reached its limit value will decrease for each of the boom cylinder 2 and the arm cylinder 3.

[0130] Figure 19 is a flowchart detailing the processing contents of the maximum possible pump discharge pressure calculation unit 20f and the direct power limit value calculation unit 20g. Figure 20 is an explanatory diagram of the calculation principle of the maximum possible discharge pressure in the maximum possible pump discharge pressure calculation unit 20f.

[0131] First, the maximum possible pump discharge pressure calculation unit 20f determines an arbitrary pump discharge pressure Pi, assuming that the direct power of either the boom cylinder 2 or the arm cylinder 3 has reached its limit and the driving of the boom cylinder 2 and the arm cylinder 3 has stopped due to an overload condition, and that the flow rate of pressurized oil supplied to the boom cylinder 2 or the arm cylinder 3 is 0. Based on this discharge pressure Pi, the intermediate pressure Pc of the center bypass passages 15a and 15b detected by the pressure sensors 58a and 58b, and the opening area Ac of the center bypass passage of the current flow control valve, it calculates the flow rate through the center bypass using the orifice equation shown in equation (9) below (step S200).

[0132]

number

[0133] Ac: Center bypass opening area of ​​the upstream flow control valve If Pc is detected for a given pressure Pp(Pi), then Qc can be obtained from the above orifice equation. It is derived.

[0134] The opening area Ac of the center bypass passage of the flow control valve can be calculated from the operating signals of the operating devices 21a and 22a and the preset opening area characteristics of the flow control valves 11a and 12b (relationship between the operating signal and the meter-in opening area).

[0135] Next, the maximum possible pump discharge pressure calculation unit 20f determines whether the flow rate Qc passing through the center bypass under overload conditions is equal to the maximum flow rate QHmax of the hydraulic pump 10a or 10b under constant horsepower control, that is, whether the flow rate Qc is a flow rate that can be discharged by the hydraulic pump 10a or 10b (step S210). If the flow rate Qc cannot be discharged by the hydraulic pump 10a or 10b, the process returns to step S200, changes an arbitrary pump discharge pressure Pi, and repeats the processes of steps S200 and S210 until the determination in step S210 makes it possible to discharge, searching for an arbitrary pump discharge pressure Pi that makes the flow rate Qc dischargeable by the hydraulic pump 10a or 10b (where the flow rate Qc becomes equal to the maximum flow rate QHmax). If the determination in step S210 makes the flow rate Qc dischargeable by the hydraulic pump 10a or 10b, the arbitrary pump discharge pressure Pi at that time is set as the maximum possible discharge pressure (step S220).

[0136] Next, the linear power limit calculation unit 20g calculates the maximum possible linear power of the boom cylinder 2 or arm cylinder 3 by multiplying the pressure-receiving area of ​​the piston of the boom cylinder 2 or arm cylinder 3 by the maximum possible discharge pressure, assuming that the drive of the boom cylinder 2 and arm cylinder 3 has stopped and the pressure on the discharge side of the boom cylinder 2 or arm cylinder 3 is 0 (step S230).

[0137] As described above, the control calculation unit 20d uses its maximum possible linear power as the limit value of the linear power, and calculates for each of the boom cylinder 2 and arm cylinder 3 the direction in which the linear power of the hydraulic cylinder that has reached its limit value will decrease.

[0138] ~Effects~ According to this embodiment, in particular, even when the operating levers of the operating devices 21a and 22a are finely operated and the discharge pressure of the hydraulic pumps 10a and 10b does not rise to the set pressure of the relief valves 14a and 14b, the limit value of the direct force can be calculated based on the actual operating state of the hydraulic circuit, thereby more accurately setting the limit value of the actuator direct force of the boom cylinder 2 and arm cylinder 3, and enabling more efficient excavation operations.

[0139] <Fourth Embodiment> A fourth embodiment of the present invention will now be described.

[0140] Figure 21 is a perspective view of a hydraulic excavator equipped with the control system according to this embodiment.

[0141] The control system of this embodiment further includes a display device 70 installed inside the cabin 110 of the upper rotating body 103.

[0142] Furthermore, the hydraulic circuit of the hydraulic drive device according to this embodiment is the same as that of the hydraulic drive device according to the third embodiment shown in Figure 16.

[0143] Figure 22 shows the control system according to this embodiment.

[0144] In Figure 22, the controller 20 includes functional elements similar to those of the controller 20 in the third embodiment shown in Figure 18, including a maximum possible pump discharge pressure calculation unit 20f and a control calculation unit 20d.

[0145] As described above, the controller 20 calculates the maximum possible discharge pressure of hydraulic pumps 10a and 10b, respectively, which are limited by the maximum horsepower Hmax, assuming that the direct force of either the boom cylinder 2 or the arm cylinder 3 is in an overload state where it has reached its limit, based on the operation signals of the operating devices 21a and 22a, the detection signals of the pressure sensors 58a and 58b, and the maximum horsepower Hmax of the pump control characteristics.

[0146] However, in this embodiment, the maximum possible discharge pressure calculated by the maximum possible pump discharge pressure calculation unit 20f is sent not only to the direct power limit value calculation unit 20g but also to the control calculation unit 20d.

[0147] Furthermore, the control calculation unit 20d performs a first display process using the maximum possible direct power of the boom cylinder 2 and arm cylinder 3 calculated by the direct power limit calculation unit 20g, and performs a second display process using the discharge pressure of the hydraulic pumps 10a and 10b indicated by the detection signals of the pressure sensors 57a and 57b and the maximum possible discharge pressure calculated by the maximum possible pump discharge pressure calculation unit 20f, and outputs a command signal to the display device 70.

[0148] Figure 23 is a flowchart showing the first display process of the control calculation unit 20d.

[0149] The control calculation unit 20d determines for each cylinder whether the linear force of the boom cylinder 2 and the arm cylinder 3 has reached its limit (step S300). If the linear force of neither the boom cylinder 2 nor the arm cylinder 3 has reached its limit, the color scheme of the illustrations of the boom cylinder 2 and the arm cylinder 3 remains at the default color (standard color) (step S310). On the other hand, when the linear force of either the boom cylinder 2 or the arm cylinder 3 has reached its limit, the control calculation unit 20d outputs a command signal to the display device 70 and changes the color scheme of the illustration of the hydraulic cylinder whose linear force has reached its limit from the default color (step S320).

[0150] Figure 24 is a flowchart showing the second display processing of the control calculation unit 20d.

[0151] The control calculation unit 20d determines for each hydraulic pump 10a and 10b whether the discharge pressure of each pump is approaching the maximum possible discharge pressure (step S350). If the discharge pressure of neither hydraulic pump 10a nor 10b is approaching the maximum possible discharge pressure, the color scheme of the illustrations of hydraulic pumps 10a and 10b remains at the default color (standard color) (step S360). On the other hand, when the discharge pressure of either hydraulic pump 10a or 10b approaches the maximum possible discharge pressure, the control calculation unit 20d outputs a command signal to the display device 70 and changes the color scheme of the illustration of the hydraulic pump whose discharge pressure is approaching the maximum possible discharge pressure from the default color (step S370).

[0152] Figure 25 shows the changes in the image displayed on the display device 70 as a result of the first and second display processing described above.

[0153] When the linear power of either the boom cylinder 2 or the arm cylinder 3 (arm cylinder 3 in the illustrated example) reaches its limit, the color scheme of the illustration of the hydraulic cylinder (arm cylinder 3) that has reached its limit changes, as shown on the right side of Figure 25. This allows the operator to visually identify which hydraulic cylinder has reached its limit.

[0154] Similarly, when the discharge pressure of either hydraulic pump 10a or 10b (hydraulic pump 10b in the illustrated example) approaches the maximum possible discharge pressure, the color scheme of the illustration of the hydraulic pump whose discharge pressure is approaching the maximum possible discharge pressure (hydraulic pump 10b in the illustrated example) changes, as shown on the left side of Figure 25, allowing the operator to visually identify which hydraulic pump's discharge pressure is approaching the maximum possible discharge pressure.

[0155] In this embodiment, the load status of the hydraulic pumps 10a and 10b during excavation, as well as the load status of the boom cylinder 2 and arm cylinder 3, were displayed on the display device 70. However, only one of them may be displayed.

[0156] ~Effects~ According to this embodiment, the operator can visually identify the hydraulic pump whose discharge pressure is approaching the maximum possible discharge pressure, or the hydraulic cylinder whose direct power has reached its limit. This allows the operator to appropriately grasp the load state of the hydraulic pumps 10a, 10b and / or the boom cylinder 2 and arm cylinder 3 during excavation, thereby further improving operational efficiency.

[0157] <Other> In the above embodiment, when calculating the direction in which the linear force of the boom cylinder 2 and arm cylinder 3 decreases when they reach their limit, the excavation reaction force vector was calculated using the respective postures of the boom cylinder 2 and arm cylinder 3 detected by IMUs 27 and 28. However, in addition to posture, the excavation reaction force vector may also be calculated using the velocity, acceleration, and equations of motion of the boom cylinder 2 and arm cylinder 3.

[0158] The velocity and acceleration of the boom cylinder 2 and arm cylinder 3 may be detected, for example, by the IMUs 27 and 28 that detect attitude, or by using independent velocity sensors and acceleration sensors. Furthermore, if the attitude of the boom cylinder 2 and arm cylinder 3 is measured by the angle sensors of the rotary joint, the velocity and acceleration may be obtained by differentiating the angle information from the angle sensors.

[0159] By calculating the excavation reaction force vector including the velocity and acceleration of the boom cylinder 2 and arm cylinder 3, the excavation reaction force vector can be calculated more accurately. As a result, the direction in which the linear force of the boom cylinder 2 and arm cylinder 3 decreases when they reach their limit can be calculated more accurately, allowing for more efficient excavation.

[0160] Furthermore, although the above embodiment described the case where the work machine is a hydraulic excavator, the work machine may be any other work machine (for example, a wheeled hydraulic excavator, hydraulic crane, wheel loader, etc.) as long as it has a vehicle body and a front work machine equipped with a boom and arm. [Explanation of symbols]

[0161] 100 Hydraulic Excavators 103 Upper rotating body (vehicle body) 104 Front work equipment 105 Boom 106 Arm 107 buckets 2 Boom Cylinders 3 Arm Cylinder 4 Bucket Cylinders 10a, 10b Hydraulic pumps (first and second hydraulic pumps) 11a, 12a Flow control valves (first and second flow control valves) 12a, 12b Flow control valves (3rd and 4th flow control valves) 13a,13b Discharge oil path 14a, 14b Relief valve 15a, 15b Center Bypass Passages (First and Second Center Bypass Passages) 20 controllers 20a Direct power calculation section 20b Attitude calculation section 20c storage section 20d Control Calculation Unit 20e Lever operation direction determination unit 20f Maximum Possible Pump Discharge Pressure Calculation Unit 20g Direct Power Limit Value Calculation Unit 21,22 Operating device 21a Operating device for boom 22a Operating device for the arm 25a, 25b Pressure sensor (first sensor) 26a, 26b Pressure sensor (second sensor) 27,28 IMU (3rd and 4th sensors) 56a, 56b Regulators (First and Second Regulators) 57a, 57b Pressure sensors (7th and 8th sensors) 58a, 58b Pressure sensors (5th and 6th sensors) 70 Display device

Claims

1. The car body and A front working machine including a boom that rotates vertically relative to the vehicle body and an arm that rotates vertically relative to the boom; a boom cylinder connected to the vehicle body and the boom and driving the boom in a vertical direction relative to the vehicle body; an arm cylinder connected to the boom and the arm and driving the arm in a vertical direction relative to the boom; A first operating device that generates an operating signal that instructs an operation of the boom; A second operating device that generates an operating signal that instructs an operation of the arm; A first sensor for detecting a parameter related to a linear force of the boom cylinder; A second sensor for detecting a parameter related to the linear force of the arm cylinder; A third sensor for detecting the attitude of the boom; A fourth sensor for detecting the posture of the arm, a controller that controls driving of the boom cylinder and the arm cylinder based on operation signals of the first operating device and the second operating device, detection signals of the first sensor and the second sensor, and detection signals of the third sensor and the fourth sensor, The controller when the first operating device and the second operating device are operated simultaneously to perform a combined operation of simultaneously driving the boom and the arm, a linear force of each of the boom cylinder and the arm cylinder is calculated based on the detection signals of the first sensor and the second sensor; a control circuit for controlling the drive of the boom cylinder and the arm cylinder so that, when either one of the linear forces of the boom cylinder and the arm cylinder reaches a limit value, a direction in which the linear force that has reached the limit value will decrease is calculated based on the detection signals of the third sensor and the fourth sensor and the respective linear forces of the boom cylinder and the arm cylinder, and the excavation operating point of the front work machine moves in the direction in which the linear force is decreased.

2. 2. The working machine according to claim 1, The controller a working machine comprising: a hydraulic cylinder control unit configured to control a hydraulic cylinder movement direction of the working machine; a hydraulic cylinder control unit configured to control a hydraulic cylinder movement direction of the working machine; and a hydraulic cylinder control unit configured to control a hydraulic cylinder movement direction of the working machine;

3. 3. The working machine according to claim 2, The controller determining whether the operation directions of the first operating device and the second operating device are the extension direction or the retraction direction of the boom cylinder and the arm cylinder based on the operation signals of the first operating device and the second operating device; determining whether or not a range that coincides with the extension direction or retraction direction of the boom cylinder and the arm cylinder exists within a range in which the linear force reaches the limit value and decreases; When the matching range exists, the direction in which the linear force that has reached the limit value is to be reduced is calculated within the matching range, and the drive of the boom cylinder and the arm cylinder is controlled so that the excavation operating point of the front work machine moves in the direction in which the linear force is reduced, and when the matching range does not exist, the drive of the boom cylinder and the arm cylinder is stopped.

4. 2. The working machine according to claim 1, A first hydraulic pump and a second hydraulic pump of a variable displacement type; a first flow control valve of an open center type connected to a first center bypass passage connected to a discharge oil passage of the first hydraulic pump and configured to control a flow rate of pressure oil supplied from the first hydraulic pump to the boom cylinder; a second flow control valve of an open center type connected in tandem to the first center bypass passage downstream of the first flow control valve and configured to control a flow rate of pressure oil supplied from the first hydraulic pump to the arm cylinder; a third flow control valve of an open center type connected to a second center bypass passage connected to a discharge oil passage of the second hydraulic pump and controlling a flow rate of pressure oil supplied from the second hydraulic pump to the arm cylinder; a fourth flow control valve of an open center type connected in tandem to the second center bypass passage downstream of the third flow control valve and configured to control a flow rate of pressure oil supplied from the second hydraulic pump to the boom cylinder; a first regulator that controls a discharge flow rate of the first hydraulic pump so that the absorption horsepower of the first hydraulic pump does not exceed a preset maximum horsepower; a second regulator that controls a discharge flow rate of the second hydraulic pump so that the absorption horsepower of the second hydraulic pump does not exceed a preset maximum horsepower; a fifth sensor that detects an intermediate pressure of pressure oil flowing through the first center bypass passage between the first flow control valve and the second flow control valve; a sixth sensor that detects an intermediate pressure of pressure oil flowing through the second center bypass passage between the third flow control valve and the fourth flow control valve, The controller storing pump control characteristics including the setting of the maximum horsepower used in controlling the first regulator and the second regulator; calculates a maximum possible discharge pressure of each of the first hydraulic pump and the second hydraulic pump, which is limited by the maximum horsepower, based on the detection signals of the first operating device and the second operating device, the detection signals of the fifth sensor and the sixth sensor, and the maximum horsepower of the pump control characteristics, when it is assumed that the direct force of either the boom cylinder or the arm cylinder is in an overload state in which it has reached the limit value; a maximum possible linear force of each of the boom cylinder and the arm cylinder is calculated by multiplying the pressure-receiving area of ​​the piston of each of the boom cylinder and the arm cylinder by the maximum possible discharge pressure, and the maximum possible linear force is used as a limit value of the linear force, and a direction in which the linear force of the hydraulic cylinder that has reached the limit value is reduced is calculated for each of the boom cylinder and the arm cylinder.

5. 2. The working machine according to claim 1, a display device that displays an illustration of the front working implement including the boom, the arm, the boom cylinder, and the arm cylinder, The controller a work machine which judges for each cylinder whether the linear force of the boom cylinder and the arm cylinder has reached the limit value, and when the linear force of either the boom cylinder or the arm cylinder has reached the limit value, changes the color scheme of an illustration of the corresponding boom cylinder and arm cylinder.

6. 2. The working machine according to claim 1, A first hydraulic pump and a second hydraulic pump of a variable displacement type; a first flow control valve of an open center type connected to a first center bypass passage connected to a discharge oil passage of the first hydraulic pump and configured to control a flow rate of pressure oil supplied from the first hydraulic pump to the boom cylinder; a second flow control valve of an open center type connected in tandem to the first center bypass passage downstream of the first flow control valve and configured to control a flow rate of pressure oil supplied from the first hydraulic pump to the arm cylinder; a third flow control valve of an open center type connected to a second center bypass passage connected to a discharge oil passage of the second hydraulic pump and controlling a flow rate of pressure oil supplied from the second hydraulic pump to the arm cylinder; a fourth flow control valve of an open center type connected in tandem to the second center bypass passage downstream of the third flow control valve and configured to control a flow rate of pressure oil supplied from the second hydraulic pump to the boom cylinder; a first regulator that controls a discharge flow rate of the first hydraulic pump so that the absorption horsepower of the first hydraulic pump does not exceed a preset maximum horsepower; a second regulator that controls a discharge flow rate of the second hydraulic pump so that the absorption horsepower of the second hydraulic pump does not exceed a preset maximum horsepower; a fifth sensor that detects an intermediate pressure of pressure oil flowing through the first center bypass passage between the first flow control valve and the second flow control valve; a sixth sensor that detects an intermediate pressure of pressure oil flowing through the second center bypass passage between the third flow control valve and the fourth flow control valve; A seventh sensor that detects a discharge pressure of the first hydraulic pump; an eighth sensor that detects a discharge pressure of the second hydraulic pump; a display device that displays an illustration of the front working implement including the boom, the arm, the boom cylinder, and the arm cylinder, The controller storing pump control characteristics including a maximum horsepower setting used in controlling the first regulator and the second regulator; calculates a maximum possible discharge pressure of each of the first hydraulic pump and the second hydraulic pump, which is limited by the maximum horsepower, based on the detection signals of the first operating device and the second operating device, the detection signals of the fifth sensor and the sixth sensor, and the maximum horsepower of the pump control characteristics, when it is assumed that the direct force of either the boom cylinder or the arm cylinder is in an overload state in which it has reached the limit value; a determination is made for each pump as to whether the discharge pressure of the first hydraulic pump detected by the seventh sensor and the discharge pressure of the second hydraulic pump detected by the eighth sensor are approaching the maximum possible discharge pressure, and when the discharge pressure of either the first hydraulic pump or the second hydraulic pump approaches the maximum possible discharge pressure, a color scheme of an illustration of the hydraulic pump whose discharge pressure is approaching the maximum possible discharge pressure is changed.

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