Construction machine

Abstract

To provide a construction machine capable of reducing load of a work device in an appropriate situation without using a sensor to detect stress.SOLUTION: A hydraulic driving circuit 30 for a hydraulic shovel 1A is placed in a line connecting a pump 31 and an oil storage tank 32 storing hydraulic oil, having a relief valve 35 controlling relief pressure as an upper limit value of pumping pressure of the pump 31. The control device 50 sets the relief pressure at a lower pressure when the work device 20 is determined to be operated at a specific high load state than when the work device is determined not to be operated in the specific high load state on the basis of detected values of a posture sensor and a force sensor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a construction machine, and more particularly to a construction machine that suppresses operation of a working implement under a high load condition. [Background technology]

[0002] Conventionally, there are known techniques for suppressing operation of the working equipment (front structure) of construction machinery under high load conditions. For example, Patent Document 1 describes an operation system for a hydraulic excavator in which strain gauges are provided on the boom and arm, and when the load signal detected by the strain gauges exceeds a standard, the operation signal of the pilot valve (proportional solenoid valve) of the hydraulically operated control valve of the boom cylinder or arm cylinder is restricted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-72636 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to accurately detect the load on the working equipment of the construction machine, a large number of sensors such as strain gauges are required to detect the strain acting on the working equipment, in other words, sensors to detect stress. This requires a large amount of labor-intensive work, such as wiring the lead wires, removing the surface paint from the sensor mounting parts with a grinder, and performing rust-proofing and waterproofing treatments after mounting the sensors, resulting in a heavy workload. In addition, if an abnormality such as a broken lead wire occurs, repair and replacement work is required. Furthermore, the lifespan of the sensors means that they are not suitable for long-term use.

[0005] On the other hand, without a sensor for detecting stress, it is difficult to properly determine whether the working equipment is being operated under high load. Therefore, if the amount of hydraulic oil in the boom cylinder or arm cylinder is restricted without proper determination, as in the hydraulic excavator described in Patent Document 1, this may lead to a decrease in the amount of work. Therefore, it is required to properly determine the situation in which the load on the working equipment should be reduced.

[0006] The present invention has been made in consideration of these problems, and its object is to provide a construction machine that can reduce the load on a working implement in appropriate situations without using a sensor to detect stress. [Means for solving the problem]

[0007] In order to achieve the above object, a construction machine of the present invention includes a work implement having a work machine body, a boom rotatable relative to the work machine body, an arm rotatable relative to the boom, and a work tool rotatable relative to the arm, a hydraulic drive circuit having a plurality of hydraulic actuators for driving the work implement and a pump for supplying hydraulic oil to the hydraulic actuators, an attitude sensor for detecting the attitude of the work implement, a force sensor for detecting a force acting on the work implement, and a control device for controlling the hydraulic drive circuit, wherein the force sensor is a sensor for detecting the pressure of hydraulic oil supplied to the hydraulic actuator, the hydraulic drive circuit has a relief valve disposed on a path connecting the pump and a storage tank for storing hydraulic oil and defining a relief pressure as an upper limit value for the discharge pressure of the pump, and the control device sets the relief pressure to a lower value when it is determined based on the detection values ​​of the attitude sensor and the force sensor that the work implement is being operated under a predetermined high-load condition compared to when it is determined that the work implement is not being operated under the predetermined high-load condition. Effect of the Invention

[0008] According to the construction machine of the present invention, it is possible to reduce the load on the work implement in appropriate situations without using a sensor for detecting stress. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a hydraulic excavator as a construction machine. [Diagram 2] FIG. 2 is a schematic diagram showing a hydraulic drive circuit. [Diagram 3] FIG. 2 is a schematic diagram showing a plurality of sensors and a control device. [Figure 4] 5 is a flowchart showing an example of a load reduction control process executed by the control device in the first embodiment. [Diagram 5] 1 is an explanatory diagram illustrating a state in which the working device is operating in a high-load position; FIG. [Figure 6] FIG. 11 is a schematic configuration diagram showing a control device and a plurality of sensors provided in a hydraulic excavator according to a second embodiment. [Figure 7] 10 is a flowchart showing an example of a load reduction control process executed by the control device in the second embodiment. [Figure 8] 3 is an explanatory diagram illustrating a schematic diagram of each part of a working device for which stress is calculated; FIG. [Figure 9] FIG. 11 is an explanatory diagram showing an example of a map defining the relationship between the accumulated damage level and a fatigue index value. [Figure 10] FIG. 13 is an explanatory diagram showing another example of the map defining the relationship between the accumulated damage level and the fatigue index value. [Figure 11] FIG. 13 is an explanatory diagram showing yet another example of the map defining the relationship between the accumulated damage level and the fatigue index value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the front-rear, left-right, and up-down directions of the construction machine will be described with reference to the driver riding on the construction machine.

[0011] [First embodiment] Fig. 1 is a schematic diagram showing a hydraulic excavator as a construction machine. The hydraulic excavator 1A shown in Fig. 1 is a construction machine used for, for example, excavating earth and sand at a construction site. The hydraulic excavator 1A includes a work machine body 10 and a work device 20.

[0012] (Work machine body) The working machine body 10 includes a lower traveling body 11 and an upper rotating body 12. The lower traveling body 11 includes a crawler 11a as a drive device for traveling the hydraulic excavator 1A. The crawler 11a is driven by a hydraulic motor for traveling (not shown). The upper rotating body 12 is provided on the lower traveling body 11 so as to be rotatable. The upper rotating body 12 is driven by a hydraulic motor for turning (not shown) to turn. A cab 13 for an operator to sit on is provided at the front of the frame 12a of the upper rotating body 12. A fuel tank 14, a machine room 15, a counterweight 16, and the like are provided behind the cab 13 of the upper rotating body 12. The machine room 15 is equipped with an engine (not shown), a hydraulic pump 31 (see FIG. 2) driven by the engine, and the like. The pump 31 pumps hydraulic oil supplied to the hydraulic motor for traveling, the hydraulic motor for turning, and each component of the working device 20, thereby operating each hydraulic device.

[0013] (Working equipment) The working device 20 is an articulated working device, and is attached to the front of the frame 12a of the upper rotating body 12. The working device 20 includes a boom 21, an arm 22, a bucket (work tool) 23, and multiple hydraulic actuators that drive the working device 20. The multiple hydraulic actuators include a hydraulic boom cylinder 24, a hydraulic arm cylinder 25, and a hydraulic bucket cylinder 26 (work tool cylinder).

[0014] The boom 21 is rotatably connected to the upper rotating body 12. The arm 22 is rotatably connected to the boom 21. The bucket 23 is a hydraulic work tool for performing excavation work and the like, and is rotatably connected to the arm 22. When the bucket 23 is replaced with a hydraulic breaker or hydraulic crusher, the replaced equipment functions as the hydraulic work tool.

[0015] The boom cylinder 24 is connected between the upper rotating body 12 and the boom 21, and is hydraulically extended and retracted to adjust the angle of the boom 21. The arm cylinder 25 is connected between the boom 21 and the arm 22, and is hydraulically extended and retracted to adjust the angle of the arm 22. The bucket cylinder 26 is connected between the arm 22 and the bucket 23, and is hydraulically extended and retracted to adjust the angle of the bucket 23. Hydraulic oil is supplied to the boom cylinder 24, arm cylinder 25 and bucket cylinder 26 from a pump 31 provided in the machine room 15 via a hydraulic hose (not shown).

[0016] In addition to the above configuration, the hydraulic excavator 1A further includes a hydraulic drive circuit 30, a plurality of sensors 40, and a control device 50, as shown in Figures 2 and 3. Figure 2 is a schematic configuration diagram showing the hydraulic drive circuit 30, and Figure 3 is a schematic configuration diagram showing the plurality of sensors 40 and the control device 50.

[0017] (Hydraulic drive circuit) The hydraulic drive circuit 30 includes the boom cylinder 24, the arm cylinder 25, the bucket cylinder 26 (see FIG. 1), a pump 31, a storage tank 32, a first flow control valve 33, a second flow control valve 34, and a relief valve 35. The pump 31, the storage tank 32, the first flow control valve 33, the second flow control valve 34, and the relief valve 35 are mounted in the machine room 15.

[0018] The boom cylinder 24 includes a bottom-side hydraulic chamber 24a, a rod-side hydraulic chamber 24b, a piston 24c, and a rod 24d. When hydraulic oil is supplied to the bottom-side hydraulic chamber 24a, the piston 24c moves toward the tip end of the cylinder tube, and hydraulic oil is discharged from the rod-side hydraulic chamber 24b, causing the rod 24d to extend. On the other hand, when hydraulic oil is supplied to the rod-side hydraulic chamber 24b, the piston 24c moves toward the base end of the cylinder tube, and hydraulic oil is discharged from the bottom-side hydraulic chamber 24a, causing the rod 24d to contract. Similarly, the arm cylinder 25 includes a bottom-side hydraulic chamber 25a, a rod-side hydraulic chamber 25b, a piston 25c, and a rod 25d. When hydraulic oil is supplied to the bottom-side hydraulic chamber 25a or the rod-side hydraulic chamber 25b, the piston 25c moves in the same manner as the boom cylinder 24, causing the rod 25d to extend or contract. Although the bucket cylinder 26 is not shown in FIG. 2, it has a similar configuration to the boom cylinder 24 and the arm cylinder 25.

[0019] As described above, the pump 31 is mounted in the machine room 15 and driven by an engine (not shown) to discharge the hydraulic oil stored in the storage tank 32. The first flow control valve 33 is connected between the pump 31 and the boom cylinder 24. The first flow control valve 33 controls the amount of hydraulic oil discharged from the pump 31 to be supplied to the bottom side hydraulic chamber 24a and the rod side hydraulic chamber 24b of the boom cylinder 24 based on an operation signal generated by the control device 50 in response to an operation angle of an operation lever (not shown) operated by the driver. The second flow control valve 34 is connected to the pump 31 via the first flow control valve 33 and is also connected to the arm cylinder 25. The second flow control valve 34 controls the amount of hydraulic oil discharged from the pump 31 to be supplied to the bottom side hydraulic chamber 25a and the rod side hydraulic chamber 25b of the arm cylinder 25 based on an operation signal generated by the control device 50 in response to an operation angle of an operation lever (not shown) operated by the driver. It should be noted that the supply passage for the hydraulic oil to the bucket cylinder 26 and the flow control valve are not shown in FIG. 2 and will not be described.

[0020] The relief valve 35 is disposed on a path connecting the pump 31 and the storage tank 32 that stores hydraulic oil, upstream of the first flow control valve 33. The relief valve 35 closes when the discharge pressure of the pump 31 is less than the relief pressure. The relief valve 35 opens when the discharge pressure of the pump 31 is equal to or greater than the relief pressure, and adjusts the discharge pressure of the pump 31 to the relief pressure by sending a part of the hydraulic oil discharged from the pump 31 to the storage tank 32. Thus, the relief valve 35 defines the relief pressure as the upper limit of the discharge pressure of the pump 31. In this embodiment, the relief valve 35 is a variable valve that opens at a set relief pressure when a relief pressure setting signal is input from the control device 50 to the relief pressure adjustment unit 35a. In the following description, the relief pressure is set to a first predetermined pressure during normal operation of the hydraulic excavator 1A, that is, in a state in which the load reduction control of the working device 20 described later is not being executed.

[0021] (Sensor) The multiple sensors 40 will be described with reference to Fig. 3. The multiple sensors 40 include an attitude sensor 410 that detects the attitude of the hydraulic excavator 1A and a force sensor 420 that detects a force acting on the hydraulic excavator 1A, which are attached to various parts of the hydraulic excavator 1A. Each sensor 40 outputs a detection value to the control device 50.

[0022] In this embodiment, the attitude sensor 410 includes an angle sensor 411 , an angular velocity sensor 412 , an acceleration sensor 413 , a tilt angle sensor 414 , and a stroke sensor 415 .

[0023] The angle sensors 411 are provided in each part of the hydraulic excavator 1A and detect, for example, the rotation angle of the upper rotating body 12 relative to the lower traveling body 11, the rotation angle of the boom 21 relative to the upper rotating body 12, the rotation angle of the arm 22 relative to the boom 21, and the rotation angle of the bucket 23 relative to the arm 22.

[0024] The angular velocity sensors 412 are provided in each portion of the hydraulic excavator 1A and detect, for example, the angular velocity of the upper rotating body 12, the angular velocity of the boom 21, the angular velocity of the arm 22, the angular velocity of the bucket 23, and the like.

[0025] The acceleration sensors 413 are provided in each portion of the hydraulic excavator 1A, and detect, for example, the acceleration of the upper rotating body 12, the acceleration of the boom 21, the acceleration of the arm 22, the acceleration of the bucket 23, and the like.

[0026] The inclination angle sensor 414 is provided in each part of the hydraulic excavator 1A and detects, for example, the inclination angle of the lower running body 11 and the upper rotating body 12 with respect to the horizontal direction, the inclination angle of the boom 21 with respect to the horizontal direction, the inclination angle of the arm 22 with respect to the horizontal direction, and the inclination angle of the bucket 23 with respect to the horizontal direction.

[0027] The stroke sensors 415 are provided in each portion of the hydraulic excavator 1A, and detect the stroke of the boom cylinder 24, the stroke of the arm cylinder 25, and the stroke of the bucket cylinder .

[0028] The force sensor 420 includes a hydraulic sensor 421 provided in each part of the hydraulic excavator 1A. The hydraulic sensor 421 detects the pressure of hydraulic oil supplied to each hydraulic actuator, such as the hydraulic pressure of the bottom side hydraulic chamber 24a and the hydraulic pressure of the rod side hydraulic chamber 24b of the boom cylinder 24, the hydraulic pressure of the bottom side hydraulic chamber 25a and the hydraulic pressure of the rod side hydraulic chamber 25b of the arm cylinder 25, and the hydraulic pressure of the bottom side hydraulic chamber and the rod side hydraulic chamber (not shown) of the bucket cylinder 26. The hydraulic sensor 421 also detects the hydraulic pressure of hydraulic oil supplied to the traveling hydraulic motor and the swing hydraulic motor, for example.

[0029] (Control device) The control device 50 is a main controller for performing overall control including drive control of the hydraulic excavator 1A. The control device 50 includes a memory device (ROM: Read Only Memory, RAM: Random Access Memory, non-volatile RAM, etc.), a central processing unit (CPU: Central Processing Unit), etc. The above-mentioned multiple sensors 40 are connected to the input side of the control device 50, and detection values ​​detected by each sensor 40 are input.

[0030] The control device 50 includes a high-load posture determination unit 52, a pressure determination unit 54, and a relief pressure setting unit 56. The high-load posture determination unit 52 determines whether or not the working device 20 is operating in a high-load posture based on the detection value of the posture sensor 410. The pressure determination unit 54 determines whether or not the hydraulic pressure of the bottom side hydraulic chamber 25a of the arm cylinder 25 is equal to or higher than a predetermined pressure based on the detection value of the hydraulic sensor 421. In the following description, the hydraulic pressure of the bottom side hydraulic chamber 25a of the arm cylinder 25 is simply referred to as the "hydraulic pressure of the arm cylinder 25". The pressure determination unit 54 may determine whether or not the hydraulic pressure of the rod side hydraulic chamber 25b of the arm cylinder 25 is equal to or higher than a predetermined pressure based on the detection value of the hydraulic sensor 421. The relief pressure setting unit 56 sets the relief pressure of the relief valve 35 according to the determination results of the high-load posture determination unit 52 and the pressure determination unit 54. The functions of the high-load posture determination unit 52, the pressure determination unit 54, and the relief pressure setting unit 56 will be described in detail in the load reduction control below.

[0031] (Load reduction control) In this embodiment, the control device 50 executes load reduction control for changing the relief pressure of the pump 31 in order to reduce the load on the working device 20 when the working device 20 is operated in a predetermined high-load state. FIG. 4 is a flowchart showing an example of the load reduction control process executed by the control device 50 in the first embodiment. The load reduction control shown in FIG. 4 is repeatedly executed by the control device 50 at predetermined time intervals while the hydraulic excavator 1A is in operation. It should be noted that, at the time when the process shown in FIG. 4 is started, the relief pressure is set to the first predetermined pressure for normal operation described above. Also, either the process of steps S2 and S3 or the process of step S4 described below may be executed first.

[0032] The control device 50 first acquires detection values ​​of the attitude sensor 410 and the force sensor 420 (step S1). More specifically, the control device 50 acquires the rotation angle of the boom 21 and the rotation angle of the arm 22 detected by the angle sensor 411 through the high-load attitude determination unit 52. The control device 50 also acquires the hydraulic pressure of the arm cylinder 25 detected by the hydraulic pressure sensor 421 through the pressure determination unit 54.

[0033] Next, the control device 50 determines whether the working device 20 is operating in a high-load posture by the processing of steps S2 and S3 in the high-load posture determination unit 52. Here, FIG. 5 is an explanatory diagram that shows a schematic state in which the working device 20 is operating in a high-load posture. In the first embodiment, the working device 20 is operating in a high-load posture when the working device 20 is operating within a predetermined operating range and performing a scraping operation in which the work target is dropped downward from a plane Z extending in the vertical direction. Note that the plane Z extending in the vertical direction may be a plane having a predetermined angle with respect to the vertical direction.

[0034] As shown by the two-dot chain line in FIG. 5, the position of the boom 21 in the most raised state relative to the upper rotating body 12, that is, the position of the boom 21 in the state where the boom cylinder 24 (see FIG. 1) is most extended, is referred to as the "first boom position B1". In addition, in a state where the arm 22 is perpendicular to the ground level GL, the position of the boom 21 in a state where the bottom end 23b of the trajectory 23a drawn by the tip of the bucket 23 touches the ground level GL is referred to as the "second boom position B2". Note that the trajectory 23a of the bucket 23 is determined in advance, and whether or not the bottom end 23b of the trajectory 23a touches the ground level GL may be determined based on the ground level GL and the trajectory 23a determined in advance. In addition, the trajectory 23a in FIG. 8 is depicted in a schematic circular shape, and does not mean that the bucket 23 rotates 360 degrees relative to the arm 22.

[0035] Furthermore, the position of the arm 22 at the arm dump end where the arm cylinder 25 is in the most contracted state is referred to as the "first arm position A1". Moreover, when the boom 21 is in the second boom position B2, the position of the arm 22 where the arm 22 is perpendicular to the ground level GL is referred to as the "second arm position A2". In the first embodiment, as shown by the solid arrow in Fig. 5, it is assumed that scraping work is being performed by the working device 20 within a predetermined operating range when the position of the boom 21 is within the range from the first boom position B1 to the second boom position B2 and the position of the arm 22 is within the range from the first arm position A1 to the second arm position A2.

[0036] Returning to the description of FIG. 4, the control device 50 determines whether or not the position of the boom 21 is within the range from the first boom position B1 to the second boom position B2 based on the detection value of the angle sensor 411 (step S2). When the control device 50 determines that the position of the boom 21 is within the range from the first boom position B1 to the second boom position B2 (Yes in step S2), the control device 50 determines whether or not the position of the arm 22 is within the range from the first arm position A1 to the second arm position A2 based on the detection value of the angle sensor 411 (step S3). When the control device 50 determines that the position of the arm 22 is within the range from the first arm position A1 to the second arm position A2 (Yes in step S3), it determines that the scraping work is being performed by the working device 20 within a predetermined operating range and that the working device 20 is operating in a high-load posture, and proceeds to the processing of step S4 and subsequent steps.

[0037] Next, the control device 50 determines whether the hydraulic pressure of the arm cylinder 25 is equal to or higher than a predetermined pressure based on the detection value of the hydraulic sensor 421 by the pressure determination unit 54 (step S4). The predetermined pressure may be set appropriately based on empirical knowledge based on, for example, experiments, analyses, and the work history of the hydraulic excavator 1A, taking into consideration the stress, damage level, fatigue level, and the like generated in each part of the arm 22.

[0038] When the control device 50 determines that the hydraulic pressure of the arm cylinder 25 is equal to or higher than the predetermined pressure (Yes in step S4), the relief pressure setting unit 56 sets the relief pressure, which is the upper limit of the discharge pressure of the pump 31 defined by the relief valve 35, to the second predetermined pressure (step S5), and executes the processing from step S1 onwards again. Here, the second predetermined pressure is a value lower than the first predetermined pressure, which is the relief pressure in the normal state described above. As a result, when the working device 20 is performing scraping work and the hydraulic pressure of the arm cylinder 25 is equal to or higher than the predetermined pressure and the load on the arm 22 is relatively large, it is determined that the working device 20 is being operated in a predetermined high load state, and the discharge pressure of the pump 31 is limited more than normal, thereby reducing the load on the working device 20.

[0039] On the other hand, when the control device 50 determines that the position of the boom 21 is not within the range from the first boom position B1 to the second boom position B2 (No in step S2), the relief pressure setting unit 56 sets the relief pressure to the first predetermined pressure in normal operation (step S6). When the control device 50 determines that the position of the arm 22 is not within the range from the first arm position A1 to the second arm position A2 (No in step S3), the relief pressure setting unit 56 sets the relief pressure to the first predetermined pressure in normal operation (step S6). When the control device 50 determines that the hydraulic pressure of the arm cylinder 25 is less than the predetermined pressure (No in step S4), the control device 50 sets the relief pressure to the first predetermined pressure in normal operation (step S6). After the process of step S6, the control device 50 executes the processes from step S10 onwards again. As a result, when the working implement 20 is not performing scraping work or when the hydraulic pressure in the arm cylinder 25 is below a predetermined pressure and the load on the arm 22 is relatively small, it is determined that the working implement 20 is not being operated under a predetermined high load condition, and the restriction of the relief pressure of the pump 31 is not performed.

[0040] (Effects of the first embodiment) As described above, the hydraulic excavator (construction machine) 1A according to the first embodiment comprises a work machine body 10, a work implement 20 having a boom 21 rotatable relative to the work machine body 10, an arm 22 rotatable relative to the boom 21, and a bucket 23 rotatable relative to the arm 22, a hydraulic drive circuit 30 having a plurality of hydraulic actuators for driving the work implement 20 and a pump 31 for supplying hydraulic oil to the hydraulic actuators, an attitude sensor 410 for detecting the attitude of the work implement 20, a force sensor 420 for detecting the force acting on the work implement 20, and a control device 50 for controlling the hydraulic drive circuit 30. The force sensor 420 is a sensor that detects the pressure of hydraulic oil supplied to the hydraulic actuator, and the hydraulic drive circuit 30 is arranged on a path that connects the pump 31 and the storage tank 32 that stores hydraulic oil, and has a relief valve 35 that specifies a relief pressure as an upper limit value of the discharge pressure of the pump 31, and the control device 50 sets the relief pressure to a lower value when it is determined that the working device 20 is operated in a predetermined high-load state based on the detection values ​​of the attitude sensor 410 and the force sensor 420 (Yes in steps S2 to S4) compared to when it is determined that the working device 20 is not operated in the predetermined high-load state (No in steps S2 to S4). That is, when the working device 20 is operated in a predetermined high-load state, the relief pressure is set to a second predetermined pressure that is lower than the first predetermined pressure in normal operation (step S5), and when the working device 20 is not operated in the predetermined high-load state, the relief pressure is set to the first predetermined pressure in normal operation (step S6).

[0041] With this configuration, it is possible to determine whether or not the working implement 20 is being operated under a predetermined high-load condition based on the detection values ​​of the attitude sensor 410 and the force sensor 420, and therefore a sensor for detecting the stress of the working implement 20 is not required. Furthermore, the relief pressure is set by the relief valve 35 so as to reduce the discharge pressure of the pump 31 only when the working implement 20 is being operated under a high-load condition, so that it is possible to prevent the excavation force from decreasing more than necessary. Therefore, according to the hydraulic excavator 1A of the first embodiment, it is possible to reduce the load on the working implement 20 in an appropriate situation without using a sensor for detecting stress.

[0042] In addition, the posture sensor 410 is an angle sensor 411 that detects the position of the boom 21 and the position of the arm 22, and the force sensor 420 is a hydraulic sensor 421 that detects the pressure of the hydraulic oil supplied to the arm cylinder 25. Based on the positions of the boom 21 and the arm 22, the control device 50 determines that the working device 20 is operating within a predetermined operating range to perform a scraping work in which the work object is dropped downward from a plane Z extending in the vertical direction, and when it determines that the pressure of the hydraulic oil supplied to the arm cylinder 25 is equal to or higher than a predetermined pressure, it determines that the working device 20 is being operated under a predetermined high-load condition.

[0043] With this configuration, it is possible to determine that a predetermined high-load state, i.e., scraping work is being performed, based on the positions of the boom 21 and the arm 22 detected by the angle sensor 411 and the pressure of the hydraulic oil supplied to the arm cylinder 25, and therefore there is no need for a sensor to detect the stress of the working device 20. Also, it is possible to reduce the load on the working device 20 during scraping work, which is a high-load posture, and to prevent a decrease in the amount of work in other situations.

[0044] In addition, when the attitude sensor 410 detects that the position of the boom 21 is within the range from the first boom position B1 in the fully raised state to the second boom position B2 in which the lowest end 23b of the trajectory 23a of the tip of the bucket 23 touches the ground level GL when the arm is perpendicular to the ground level GL, and the position of the arm 22 is within the range from the first arm position A1 at the arm dump end to the second arm position A2 in which the arm 22 is perpendicular to the ground level GL when the boom 21 is at the second boom position B2, the control device 50 determines that the working device 20 is operating within a predetermined operating range to perform scraping work.

[0045] This configuration makes it possible to appropriately determine whether or not the working device 20 is performing a scraping operation, that is, whether or not the working device 20 is operating in a high-load posture.

[0046] [Second embodiment] Next, a hydraulic excavator 1B (see FIG. 1) as a construction machine according to a second embodiment will be described. FIG. 6 is a schematic configuration diagram showing a control device and a plurality of sensors provided in the hydraulic excavator 1B according to the second embodiment. The hydraulic excavator 1B according to the second embodiment is provided with a control device 60 instead of the control device 50. Other configurations of the hydraulic excavator 1B are similar to those of the hydraulic excavator 1A, so descriptions will be omitted and the same configurations will be denoted by the same reference numerals.

[0047] The control device 60 includes a stress calculation unit 62, a damage degree calculation unit 64, a fatigue index value calculation unit 66, and a relief pressure setting unit 68. The stress calculation unit 62 calculates stress acting on a plurality of parts of the working device 20 based on the detection values ​​of the posture sensor 410 and the force sensor 420. The damage degree calculation unit 64 calculates the accumulated damage degree of the plurality of parts within a predetermined period based on the stress calculated by the stress calculation unit 62. The fatigue index value calculation unit 66 calculates a fatigue index value in which the accumulated damage degree within a predetermined period is weighted for each of the plurality of parts under a predetermined condition. The relief pressure setting unit 68 sets the relief pressure of the relief valve 35 according to the fatigue index value of each part. Details of the functions of the stress calculation unit 62, the damage degree calculation unit 64, the fatigue index value calculation unit 66, and the relief pressure setting unit 68 will be described in the load reduction control below.

[0048] (Load reduction control) FIG. 7 is a flowchart showing an example of the load reduction control process executed by the control device 60 in the second embodiment. The load reduction control shown in FIG. 7 is repeatedly executed by the control device 50 at predetermined time intervals during operation of the hydraulic excavator 1B. At the time when the process shown in FIG. 7 starts to be executed, the relief pressure is set to the first predetermined pressure in the normal state described above. In addition, the processes in steps S20 to S40 below are examples, and may be executed by using other well-known arithmetic expressions (for details, see International Publication No. WO 2021 / 064776).

[0049] First, the control device 50 acquires detection values ​​of the attitude sensor 410 and the force sensor 420 by the stress calculation unit 62 (step S10). The control device 50 stores the acquired detection values ​​of the attitude sensor 410 and the force sensor 420 in a storage device (not shown).

[0050] Next, the control device 50 uses the stress calculation unit 62 to calculate the stress acting on each part of the working device 20 based on the detection values ​​of the attitude sensor 410 and the force sensor 420 (step S20). FIG. 8 is an explanatory diagram that shows each part of the working device 20 for which stress is to be calculated. As shown as parts 71 to 76 in the figure, parts of the components included in the working device 20, such as the boom 21, the arm 22, and the bucket 23, the boom cylinder 24 (see FIG. 1), the arm cylinder 25, and the bucket cylinder 26, and various other link mechanisms, are the parts for which stress is to be calculated. FIG. 8 shows the parts that are the targets diagrammatically, and in reality, for example, tens to hundreds of parts can be set for each part.

[0051] The stress calculation unit 62 calculates the stress for each of the above parts using a pre-stored stress calculation formula, such as a multiple regression formula or a regression formula using machine learning. An example of the stress calculation formula is shown in formula (1). In formula (1), "σ" is the stress of each part, "s" is the output of the posture sensor 410 and the force sensor 420, and "M" and "A" are constants based on the characteristics of each part. Note that the stress calculation formula is not limited to the one exemplified in formula (1), and any calculation formula based on a well-known method may be used (for details, see International Publication No. 2021 / 064776).

[0052]

number

[0053] Next, the control device 60 uses the damage degree calculation unit 64 to calculate the cumulative damage degree of each part within a predetermined period (step S30). The damage degree calculation unit 64 calculates the cumulative damage degree within the predetermined period based on the time history stress waveform of the stress of each part calculated in step S20 and the SN diagram of the stress amplitude and the number of repetitions. The cumulative damage degree can be calculated by Miner's rule or modified Miner's rule shown in the following formula (2) after frequency analysis of the time history stress waveform using, for example, the range pair method, the peak valley method, the rainflow method, etc. The predetermined period is a period from a certain point in the past to the present, and is, for example, about one month, but can be set to any period such as several days, several weeks, or several months.

[0054]

number

[0055] Next, the control device 60 uses the fatigue index value calculation unit 66 to calculate a fatigue index value for each part (step S40). The fatigue index value indicates the fatigue level of each part obtained by weighting the cumulative damage level calculated in step S30 under a predetermined condition, in other words, the cumulative load of each part. The fatigue index value calculation unit 66 stores a map that predefines the relationship between the cumulative damage level and the fatigue index value, and obtains a fatigue index value corresponding to the cumulative damage level of each part calculated in step S40 based on the map.

[0056] FIG. 9 is an explanatory diagram showing an example of a map that defines the relationship between the cumulative damage degree and the fatigue index value. FIG. 10 is an explanatory diagram showing another example of a map that defines the relationship between the cumulative damage degree and the fatigue index value. FIG. 11 is an explanatory diagram showing yet another example of a map that defines the relationship between the cumulative damage degree and the fatigue index value. For example, in the example shown in FIG. 9, the fatigue index value is set to Lv.1 when the cumulative damage degree is 0.0 or more and less than 0.35, Lv.2 when the cumulative damage degree is 0.35 or more and less than 0.45, Lv.3 when the cumulative damage degree is 0.45 or more and less than 0.55, Lv.4 when the cumulative damage degree is 0.55 or more and less than 0.65, and Lv.5 when the cumulative damage degree is 0.65 or more. On the other hand, the example shown in FIG. 10 has a larger range in which the fatigue index value is set to Lv.1 compared to the example shown in FIG. 9. Also, the example shown in FIG. 11 is an example in which the fatigue index value increases every time the cumulative damage degree increases by 0.2 to 0.25.

[0057] The fatigue index value calculation unit 66 selects a map such as those illustrated in Figures 9 to 11 for each part based on predetermined conditions including the components of the hydraulic excavator 1B and the working implement 20, the usage environment for each part, material properties, and other conditions, and obtains a fatigue index value corresponding to the accumulated damage level from the map.

[0058] The predetermined condition may include, for example, the degree of agreement between the stress of each part obtained by calculation and the actual stress acting on each part. The actual stress acting on each part may be empirically determined based on the work history of the hydraulic excavator 1B, for example, or may be obtained by experiment using a sensor such as a strain gauge. As the degree of agreement is lower, that is, as the calculation accuracy of the stress is lower, it is possible to select a map (e.g., FIG. 9) in which the fatigue index value increases relatively quickly in response to an increase in the cumulative damage level.

[0059] The predetermined condition may include, for example, the risk of breakage occurring for each part. That is, the risk of breakage occurring for each part may be set and stored in advance, and a map corresponding to the risk may be selected for each part. It is possible to select a map (e.g., FIG. 9) in which the fatigue index value increases relatively quickly in response to an increase in the cumulative damage level as the risk of breakage increases.

[0060] Furthermore, the predetermined condition may include, for example, the degree of impact when damage occurs in each part. The degree of impact may be set in advance in consideration of, for example, the fact that the operation of the hydraulic excavator 1B will be stopped or there is a concern that it will be stopped. The greater the degree of impact when damage occurs in the part, the more feasible it is to select a map (for example, FIG. 9) in which the fatigue index value increases relatively quickly in response to an increase in the cumulative damage degree. Furthermore, the degree of impact may be, for example, the degree of impact on safety when damage occurs in each part. In the case where the part is a safety-related part included in a safety-related component, it is possible to select a map (for example, FIG. 9) in which the fatigue index value increases relatively quickly in response to an increase in the cumulative damage degree.

[0061] The predetermined conditions may include the replacement time or repair time of parts including each part. When the replacement time or repair time of parts including each part is long or when the difficulty is high, such as when a different work vehicle is required, it is possible to select a map (e.g., FIG. 9) in which the fatigue index value increases relatively quickly in accordance with an increase in the cumulative damage level. The predetermined conditions may be conditions that take into consideration various items, such as the accessibility to the work site, the psychological impact on the user, how the hydraulic excavator 1B is used, and the impact of excavated materials.

[0062] Returning to the explanation of Fig. 7, when the control device 60 calculates the fatigue index value described above, the relief pressure setting unit 68 determines whether or not the fatigue index value of any part is equal to or greater than the first threshold value (step S50). When the control device 60 determines that the fatigue index value of any part is equal to or greater than the first threshold value (Yes in step S50), the relief pressure setting unit 68 sets the relief pressure, which is the upper limit of the discharge pressure of the pump 31 defined by the relief valve 35, to a second predetermined pressure (step S60). As in the first embodiment, the second predetermined pressure is a value lower than the first predetermined pressure, which is the relief pressure during normal operation described above.

[0063] As a result, if the fatigue index value of any part is greater than the first threshold value, it is determined that the working device 20 has been operated in a predetermined high-load state within the predetermined period, and the discharge pressure of the pump 31 is restricted more than usual, thereby reducing the load on the working device 20. In the following description, the part whose fatigue index value is determined to be equal to or greater than the first threshold value in step S50, i.e., the part that has been subjected to a relatively large load within the predetermined period, is referred to as the "corresponding part."

[0064] When the control device 60 determines that the fatigue index values ​​of all parts are less than the first threshold value (No in step S50), it determines whether or not the relief pressure is set to a second predetermined pressure (step S70). When the control device 60 determines that the relief pressure is set to the second predetermined pressure (Yes in step S70), it determines whether or not the fatigue index value of the corresponding part has decreased to less than the second threshold value (step S80). The second threshold value is a value at which the fatigue index value of the corresponding part has decreased sufficiently to the extent that it is determined that it is not necessary to decrease the relief pressure of the pump 31 below normal, and is set to a value lower than the first threshold value.

[0065] When the control device 60 determines that the fatigue index value of the relevant part has decreased to less than the second threshold value (Yes in step S80), the control device 50 sets the relief pressure to the first predetermined pressure for normal use by the relief pressure setting unit 56 (step S90). After that, the control device 50 executes the processes from step S10 onwards again. As a result, if the load on the relevant part has decreased sufficiently, it is determined that the working device 20 has not been operated in a predetermined high load state within a predetermined period of time, and the restriction on the relief pressure of the pump 31 is released.

[0066] On the other hand, when the control device 60 determines in step S80 that the fatigue index value of the relevant part has not decreased to less than the second threshold value (No in step S80), it omits the process of step S90, maintains the relief pressure at the second predetermined pressure, and executes the processes from step S10 onwards again. This allows the restriction of the relief pressure of the pump 31 to continue.

[0067] Furthermore, when the control device 60 determines in step S70 that the relief pressure is not set to the second predetermined pressure, i.e., that the relief pressure is set to the first predetermined pressure (No in step S70), it omits the processes of steps S80 and S90 and executes the processes of step S10 and after again. In other words, when the fatigue index values ​​of all parts are less than the first threshold value and the relief pressure of the pump 31 is not limited, the relief pressure is maintained at the first predetermined pressure in normal times.

[0068] (Effects of the second embodiment) As described above, in the hydraulic excavator (construction machine) 1B of the second embodiment, the control device 60 calculates the stress acting on multiple parts of the working implement 20 based on the detection values ​​of the attitude sensor 410 and the force sensor 420, calculates the accumulated damage level of the multiple parts within a predetermined period based on the calculated stress, and determines whether the working implement 20 is being operated under a predetermined high-load state based on the calculated accumulated damage level within the predetermined period. In other words, the control device 60 determines whether the working implement 20 is being operated under a predetermined high-load state based on the fatigue index value calculated from the accumulated damage level within the predetermined period.

[0069] With this configuration, it is possible to determine whether or not the working implement 20 is being operated under a predetermined high load condition based on the cumulative damage level of the working implement 20 within a predetermined period of time calculated based on the detection values ​​of the attitude sensor 410 and the force sensor 420, and therefore a sensor for detecting the stress of the working implement 20 is not required. In addition, the relief pressure is set by the relief valve 35 so as to reduce the discharge pressure of the pump 31 only when the working implement 20 is being operated under a high load condition, so that it is possible to prevent the excavation force from decreasing more than necessary. Therefore, similar to the hydraulic excavator 1A of the first embodiment, the hydraulic excavator 1B of the second embodiment also makes it possible to reduce the load on the working implement 20 in an appropriate situation without using a sensor for detecting stress.

[0070] In addition, the control device 60 calculates a fatigue index value by weighting the cumulative damage level within a specified period of time for each of multiple parts under specified conditions, and when the fatigue index value is equal to or greater than a first threshold value, it determines that the working device 20 is being operated under a specified high-load condition.

[0071] With this configuration, it is possible to determine whether the working device 20 is being operated in a high-load state by evaluating a fatigue index value weighted for each of the multiple parts under a predetermined condition, i.e., the cumulative load of each part according to the predetermined condition. In other words, by using a fatigue index value that takes into account, for example, the risk of damage and its impact, the risk and impact can be reflected in the determination of the high-load state without setting multiple first thresholds for each part. Therefore, it is possible to more appropriately determine whether the working device 20 is being operated in a high-load state.

[0072] In addition, the control device 60 determines that the working device 20 is not being operated in a specified high-load state when the fatigue index values ​​of all parts are less than the first threshold value and, for a part (relevant part) whose fatigue index value is determined to be equal to or greater than the first threshold value, the fatigue index value decreases to less than a second threshold value that is lower than the first threshold value.

[0073] With this configuration, when the load on a part that has been subjected to a relatively large load within a predetermined period and for which the fatigue index value is determined to be equal to or greater than the first threshold value has decreased sufficiently, the restriction on the relief pressure of the pump 31 can be released. As a result, the working implement 20 can be more reliably prevented from being operated under a high load.

[0074] (Modification) Although the description of the embodiment is completed above, the aspects of the present invention are not limited to this embodiment. For example, in the first embodiment, the hydraulic excavator 1A is described as an example of the construction machine, but the construction machine may have a working tool other than the bucket 23 that can perform scraping work. Also, in the second embodiment, the hydraulic excavator 1B is described as an example of the construction machine, but the construction machine may have a working tool other than the bucket 23.

[0075] In addition, in the first embodiment, the positions of the boom 21 and the arm 22 are detected based on the angle sensor 411, but the positions of the boom 21 and the arm 22 may also be detected based on the detection values ​​of the angular velocity sensor 412, the acceleration sensor 413, the inclination angle sensor 414 or the stroke sensor 415.

[0076] In the second embodiment, the fatigue index value is used to determine whether the working apparatus 20 is in a high-load state, but the accumulated damage degree calculated in step S30 of Fig. 7 may be used to determine whether the working apparatus 20 is in a high-load state. In that case, the first threshold value and the second threshold value may be set for the accumulated damage degree, and different values ​​may be set for each part.

[0077] 7 may be omitted. In other words, if the fatigue index values ​​for all parts are less than the first threshold value, it may be determined that the working implement 20 is not being operated under high load, and the relief pressure may be set to the first predetermined pressure.

[0078] In the first and second embodiments, the relief pressure is set to a second predetermined pressure lower than the first predetermined pressure in normal operation when the working device 20 is operated in a predetermined high-load state, but the method of setting the relief pressure is not limited to this. The relief pressure may be set to a lower value when the working device 20 is operated in a predetermined high-load state compared to when the working device 20 is not operated in the predetermined high-load state. For example, the relief pressure may be changed stepwise or continuously depending on the degree of load applied to the working device 20. That is, in the first embodiment, the relief pressure may be set to be lower as the hydraulic pressure of the arm cylinder 25 increases, or the relief pressure may be set to be lower as the posture is more likely to be subjected to a high load based on the position of the boom 21 or the position of the arm 22. In the second embodiment, the relief pressure may be set to be lower as the cumulative damage level or fatigue index value increases. [Explanation of symbols]

[0079] 1A, 1B Hydraulic excavator (construction machinery) 10 Work machine body 20 Working Equipment 21 Boom 22 Arm 23 Bucket (work tool) 23a Trajectory 23b Bottom end 24 Boom cylinder (hydraulic actuator) 25 Arm cylinder (hydraulic actuator) 26 Bucket cylinder (hydraulic actuator) 30 Hydraulic drive circuit 31 Pump 32 Storage Tank 33 First flow control valve 34 Second flow control valve 35 Relief valve 35a Relief pressure adjustment part 40 Sensors 410 Attitude Sensor 420 Force Sensor 50, 60 Control device 52 High load posture determination section 54 Pressure determination unit 56, 68 Relief pressure setting section 62 Stress calculation section 64 Damage degree calculation section 66 Fatigue index value calculation unit 71~76 parts A1 First arm position A2 Second arm position B1 First boom position B2 Second boom position GL Ground Level Z plane

Claims

1. A work machine body, A working device including a boom rotatable relative to the working machine body, an arm rotatable relative to the boom, and a working tool rotatable relative to the arm; a hydraulic drive circuit including a plurality of hydraulic actuators that drive the working device and a pump that supplies hydraulic oil to the hydraulic actuators; a posture sensor for detecting a posture of the working device; A force sensor that detects a force acting on the working device; A control device for controlling the hydraulic drive circuit; In a construction machine equipped with the force sensor is a sensor for detecting a pressure of hydraulic oil supplied to the hydraulic actuator, the hydraulic drive circuit has a relief valve disposed on a path connecting the pump and a storage tank that stores hydraulic oil, the relief valve defining a relief pressure as an upper limit value of a discharge pressure of the pump; A construction machine characterized in that when the control device determines that the working implement is being operated under a predetermined high-load condition based on the detection values ​​of the attitude sensor and the force sensor, it sets the relief pressure to a lower value compared to when it determines that the working implement is not being operated under the predetermined high-load condition.

2. the attitude sensor is a sensor for detecting a position of the boom and a position of the arm, the force sensor is a sensor for detecting a pressure of hydraulic oil supplied to a hydraulic arm cylinder that drives the arm, The construction machine according to claim 1, characterized in that the control device determines that the work device is operating within a predetermined operating range based on the position of the boom and the position of the arm, and that a scraping operation is being performed to drop an object of work downward from a surface extending in the vertical direction, and when it determines that the pressure of the hydraulic oil supplied to the arm cylinder is equal to or higher than a predetermined pressure, it determines that the work device is being operated in the predetermined high-load state.

3. The control device, by the attitude sensor, the boom position is within a range from a first boom position in a fully raised state to a second boom position in a state in which the bottom end of a path traced by the tip of the work tool with the arm perpendicular to the ground level is in contact with the ground level, and, when the position of the arm is detected to be within a range from a first arm position at an arm dump end to a second arm position at which the arm is perpendicular to the ground level with the boom at the second boom position, 3. The construction machine according to claim 2, wherein it is determined that the scraping operation is being performed by operating the working device within the predetermined operating range.

4. The control device includes: Calculating stresses acting on a plurality of parts of the working device based on detection values ​​of the attitude sensor and the force sensor; Calculating the cumulative damage level of the plurality of portions within a predetermined period based on the calculated stress; 2. The construction machine according to claim 1, wherein it is determined whether or not the working implement is being operated in the predetermined high-load state based on the calculated cumulative damage level within the predetermined period.

5. The construction machine according to claim 4, characterized in that the control device calculates a fatigue index value by weighting the cumulative damage level within the specified period for each of the multiple parts under specified conditions, and when the fatigue index value is equal to or greater than a first threshold value, determines that the work implement is being operated in the specified high-load state.

6. The construction machine according to claim 5, characterized in that the control device determines that the working implement is not being operated in the specified high-load state when the fatigue index values ​​of all the parts are less than the first threshold value and, for the parts whose fatigue index values ​​are determined to be greater than or equal to the first threshold value, the fatigue index value decreases to less than a second threshold value that is lower than the first threshold value.

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