Working machine and method for controlling working machine

Abstract

To accurately calculate the weight of a load carried by a work machine.SOLUTION: A work machine includes a work implement, a hydraulic cylinder that operates the work implement based on hydraulic oil, and a controller that calculates weight of a load carried by the work implement based on the pressure of the hydraulic oil supplied to the hydraulic cylinder when a pressure fluctuation of the hydraulic oil supplied to the hydraulic cylinder is smaller than a specified value.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a work machine and a method for controlling a work machine. [Background technology]

[0002] As an example of the prior art, a work amount detection device for a hydraulic excavator described in International Publication No. 03 / 033829 (Patent Document 1) is exemplified. In the hydraulic excavator, a load calculation means periodically calculates the weight of the transported object inside the bucket while the transported object is being transferred, an average value calculation means calculates an average value of the transported object weight from a predetermined number of times ago to the present, and a standard deviation calculation means calculates a standard deviation of the transported object weight from a predetermined number of times ago to the present based on the average value. Then, a true load value determination means selects the minimum standard deviation from the multiple standard deviations calculated by the standard deviation calculation means during the period from the start of the transfer of the transported object to another location to the end of the transfer, and determines the average value used in the calculation of the minimum standard deviation as the true value of the transported object weight. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO 03 / 033829 Summary of the Invention [Problem to be solved by the invention]

[0004] Hydraulic excavators perform the task of excavating soil and dumping it onto dump trucks. In order to manage the amount of soil loaded onto a dump truck, it is necessary to calculate and determine the weight of the soil in the bucket before discharging it onto the dump truck. The weight of the soil needs to be calculated while the hoist is rotating to raise the work machine while rotating, from the completion of excavation until the soil is discharged. However, due to the movement of the vehicle body, the calculated weight value is not stable and sufficient accuracy cannot be obtained.

[0005] The present disclosure proposes a work machine and a method for controlling a work machine that can accurately calculate the weight of a load carried by the work machine. [Means for solving the problem]

[0006] In accordance with the present disclosure, a work machine is proposed that includes a work machine, a hydraulic cylinder that operates the work machine based on hydraulic oil, and a controller that calculates the weight of a load carried by the work machine based on the pressure of the hydraulic oil supplied to the hydraulic cylinder when pressure fluctuations of the hydraulic oil supplied to the hydraulic cylinder are smaller than a specified value.

[0007] According to the present disclosure, a control method for a work machine is proposed. The control method includes the following steps. A first step is to detect the pressure of hydraulic oil supplied to a hydraulic cylinder that operates the work machine. A second step is to calculate the pressure fluctuation of the hydraulic oil. A third step is to calculate the weight of a load carried by the work machine based on the pressure of the hydraulic oil supplied to the hydraulic cylinder when the pressure fluctuation is smaller than a specified value. Effect of the Invention

[0008] According to the work machine and control method disclosed herein, the weight of a load carried by the work machine can be calculated with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a hydraulic excavator. [Diagram 2] 2 is a block diagram showing a schematic configuration of a system of the work machine shown in FIG. 1. [Diagram 3] FIG. 4 is a schematic diagram of a work machine for explaining moment balance. [Figure 4] 3 is a flowchart showing a control method for a work machine in an embodiment. [Diagram 5] 11 is a schematic diagram showing a first example of the timing of starting calculation and determining an average payload value. FIG. [Figure 6]FIG. 11 is a schematic diagram showing a second example of the timing for starting calculation and determining an average payload value. [Figure 7] FIG. 11 is a schematic diagram showing a third example of the timing for starting calculation and determining an average payload value. [Figure 8] FIG. 11 is a schematic diagram showing a fourth example of the timing for starting calculation and determining an average payload value. [Figure 9] FIG. 11 is a schematic diagram showing a fifth example of the timing for starting calculation and determining the average payload value. [Figure 10] FIG. 11 is a schematic diagram showing a sixth example of the timing for starting calculation and determining the average payload value. [Figure 11] FIG. 13 is a schematic diagram showing a seventh example of the timing for starting calculation and determining the average payload value. [Figure 12] FIG. 13 is a diagram showing the accuracy of payload calculation in an example and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. In the drawings, configurations may be omitted or simplified for convenience of explanation. It is also intended from the beginning that any configurations may be extracted from the embodiments and arbitrarily combined.

[0011] In the following description, the terms “up”, “down”, “front”, “rear”, “left”, and “right” are directions based on the operator seated in the driver's seat in the driver's cab 31 .

[0012] <Work machine configuration> Fig. 1 is a perspective view showing a schematic configuration of a hydraulic excavator as an example of a work machine in an embodiment. As shown in Fig. 1, a hydraulic excavator 50 in the embodiment is a large hydraulic excavator. The hydraulic excavator 50 is, for example, a mining hydraulic excavator used in mines. The hydraulic excavator 50 mainly has a traveling body 35, a rotating body 30, and a working machine 40. The traveling body 35 and the rotating body 30 form a work vehicle main body.

[0013] The traveling body 35 has a pair of left and right track belt devices 36. Each of the pair of left and right track belt devices 36 has tracks. The pair of left and right tracks are rotationally driven to cause the hydraulic excavator 50 to self-propel.

[0014] The rotating body 30 is installed so as to be freely rotatable with respect to the running body 35. The rotating body 30 can rotate about a rotation center. The rotating body 30 mainly includes a cab 31, an engine room 32, a counterweight 33, and an access system 34.

[0015] The operator's cab 31 is disposed on the front left side (vehicle front side) of the revolving body 30. In the internal space of the operator's cab 31, a driver's seat for an operator to sit on is disposed.

[0016] The engine room 32 and the counterweight 33 are each disposed on the rear side (vehicle rear side) of the rotating body 30. The engine room 32 houses an engine unit (engine, exhaust treatment structure, etc.). The upper part of the engine room 32 is covered by an engine hood. The counterweight 33 is disposed behind the engine room 32.

[0017] The access system 34 is disposed on a side, for example, the left side, of the rotating bed 30. The access system 34 is provided for an operator to enter the cab 31 from the ground and to exit the cab 31 to the ground.

[0018] The work implement 40 is supported on the front side of the revolving structure 30. The work implement 40 has, for example, a boom 41, an arm 42, a bucket 43, etc. The base end of the boom 41 is rotatably connected to the revolving structure 30 by a boom foot pin 47 (Figure 3). The base end of the arm 42 is rotatably connected to the tip of the boom 41 by a boom tip pin 48. The bucket 43 is rotatably connected to the tip of the arm 42 by an arm tip pin 49 (Figure 3; part where the bucket 43 is supported by the arm 42). The work implement 40 has the bucket 43 at its tip. The bucket 43 is an example of an attachment that is detachably mounted to the tip of the work implement 40.

[0019] The boom 41 can be driven by a boom cylinder 44. The arm 42 can be driven by an arm cylinder 45. The bucket 43 can be driven by a bucket cylinder 46. The boom cylinder 44, the arm cylinder 45 and the bucket cylinder 46 are hydraulic cylinders that operate the work implement 40 using hydraulic oil. The boom 41, the arm 42 and the bucket 43 are each driven by a hydraulic cylinder, thereby driving the work implement 40.

[0020] <Overview of the work machine system> Fig. 2 is a block diagram showing a schematic configuration of the system of the work machine shown in Fig. 1. The system in the embodiment is a system for calculating the weight of a load in a bucket 43. The system in the embodiment includes a hydraulic excavator 50 as an example of the work machine shown in Fig. 1, and a controller 10 shown in Fig. 2. The controller 10 may be mounted on the hydraulic excavator 50, or may be installed in a remote location away from the hydraulic excavator 50.

[0021] The bucket IMU (Inertial Measurement Unit) 11 is attached to a bucket link that connects the bucket cylinder 46 and the bucket 43. The bucket IMU 11 detects the acceleration of the bucket 43 in the front-rear, left-right, and up-down directions, and the angular velocity of the bucket 43 around the front-rear, left-right, and up-down directions. From the detection values ​​of the bucket IMU 11, the angle of the bucket 43 with respect to the arm 42 (bucket angle A3; see FIG. 3) is calculated.

[0022] The bucket angle A3 may be detected by an angle sensor attached around the arm tip pin 49. The angle sensor may be a potentiometer or a rotary encoder. Alternatively, a bucket cylinder stroke sensor that detects the amount of displacement of a cylinder rod with respect to the cylinder in the bucket cylinder 46 may be attached to the bucket cylinder 46, and the bucket angle A3 may be calculated from the detection value of the bucket cylinder stroke sensor.

[0023] The arm IMU 12 is attached to the arm 42. The arm IMU 12 detects the acceleration of the arm 42 in the front-rear, left-right, and up-down directions, and the angular velocity of the arm 42 about the front-rear, left-right, and up-down directions. The angle of the arm 42 with respect to the boom 41 (arm angle A2; see FIG. 3) is calculated from the detection values ​​of the arm IMU 12.

[0024] The arm angle A2 may be detected by an angle sensor attached around the boom tip pin 48. The angle sensor may be a potentiometer or a rotary encoder. Alternatively, an arm cylinder stroke sensor that detects the amount of displacement of a cylinder rod relative to the cylinder in the arm cylinder 45 may be attached to the arm cylinder 45, and the arm angle A2 may be calculated from the detection value of the arm cylinder stroke sensor.

[0025] The boom IMU 13 is attached to the boom 41. The boom IMU 13 detects the acceleration of the boom 41 in the forward / backward, left / right, and up / down directions, and the angular velocity of the boom 41 about the forward / backward, left / right, and up / down directions. From the detection values ​​of the boom IMU 13, the angle of the boom 41 with respect to the rotating structure 30 (boom angle A1; see FIG. 3 ) is calculated.

[0026] Boom angle A1 may be detected by an angle sensor attached around boom foot pin 47. The angle sensor may be a potentiometer or a rotary encoder. Alternatively, a boom cylinder stroke sensor that detects the amount of displacement of a cylinder rod relative to the cylinder in boom cylinder 44 may be attached to boom cylinder 44, and boom angle A1 may be calculated from the detection value of the boom cylinder stroke sensor.

[0027] The rotating structure IMU 14 is attached to the rotating structure 30. The rotating structure IMU 14 measures the acceleration of the rotating structure 30 in the forward / backward, left / right, and up / down directions, and the angular velocity of the rotating structure 30 about the forward / backward, left / right, and up / down directions.

[0028] The boom cylinder bottom pressure sensor 15 is attached to the bottom side of the boom cylinder 44 and detects the pressure of hydraulic oil in the cylinder bottom side oil chamber of the boom cylinder 44 (bottom pressure). The boom cylinder head pressure sensor 16 is attached to the head side of the boom cylinder 44 and detects the pressure of hydraulic oil in the cylinder head side oil chamber of the boom cylinder 44 (head pressure).

[0029] The left working implement lever 17 and the right working implement lever 18 are disposed in the cab 31. The left working implement lever 17 and the right working implement lever 18 are operated by an operator seated in the cab 31. The left working implement lever 17 and the right working implement lever 18 are operated to operate the working implement 40 and the rotating body 30. The left working implement lever 17 and the right working implement lever 18 are, for example, electric type operating levers. The left working implement lever 17 and the right working implement lever 18 may also be pilot hydraulic type operating levers.

[0030] The left working implement lever 17 is disposed to the left of the driver's seat. An operator seated in the driver's seat grips the left working implement lever 17 with his left hand to operate the left working implement lever 17. The left working implement lever 17 operates the arm 42 and the rotating body 30. The left working implement lever 17 receives input from the operator regarding the rotation direction of the rotating body 30 and the up and down movement of the arm 42. Operation of the left working implement lever 17 in the left and right directions corresponds to the rotation of the rotating body 30, and left and right rotation operations of the rotating body 30 are performed in response to the left and right direction operation. Operation of the left working implement lever 17 in the front and rear directions corresponds to the movement of the arm 42, and upward and downward movements of the arm 42 are performed in response to the front and rear direction operation.

[0031] The right work implement lever 18 is disposed to the right of the driver's seat. An operator seated in the driver's seat grips the right work implement lever 18 with his right hand and operates the right work implement lever 18. The boom 41 and the bucket 43 are operated by the right work implement lever 18. The right work implement lever 18 receives input from the operator regarding the up and down movement of the boom 41 and the up and down movement of the bucket 43. Forward and backward operation of the right work implement lever 18 corresponds to the movement of the boom 41, and the boom 41 is raised and lowered in response to the forward and backward operation. Left and right operation of the right work implement lever 18 corresponds to the movement of the bucket 43, and the bucket 43 is moved downward and upward in response to the left and right operation.

[0032] The above-described operation patterns of the left working implement lever 17 and the right working implement lever 18 are merely examples and are not intended to be limiting. The operations of the left working implement lever 17 and the right working implement lever 18 in the front-rear and left-right directions may correspond to actions different from those described above.

[0033] Detection signals from the IMUs 11-14 and the pressure sensors 15, 16 are input to the controller 10. Detection signals indicating the operation amounts of the work machine levers 17, 18 are input to the controller 10. The controller 10 is, for example, a computer, a server, a mobile terminal, or the like, and may be a CPU (Central Processing Unit).

[0034] <Calculation of the weight of the load in bucket 43> A method for calculating the weight of a load carried by the work implement 40 will now be described. Fig. 3 is a schematic diagram of the work implement 40 for explaining moment balance. As shown in Fig. 3, in this embodiment, the weight value W of the load currently in the bucket 43 is detected from the balance of each moment about the boom foot pin 47. Here, the balance of each moment about the boom foot pin 47 is expressed by the following formula (1).

[0035]

number

[0036] In formula (1), Mboomcyl is the moment around the boom foot pin 47 generated by the pressure of the hydraulic oil supplied to the boom cylinder 44. Mboom is the moment around the boom foot pin 47 due to the weight of the boom 41. Marm is the moment around the boom foot pin 47 due to the weight of the arm 42. Mbucket is the moment around the boom foot pin 47 due to the weight of the bucket 43. W is the weight of the current load in the bucket 43. L is the horizontal distance from the boom foot pin 47 to the center of gravity C4 of the load in the bucket 43. Here, the center of gravity of the load when a load of the rated load is loaded in the bucket 43 is stored in the memory unit of the controller 10 as the center of gravity C4 of the load. W×L is the moment around the boom foot pin 47 of the load in the bucket 43.

[0037] Mboomcyl is calculated from the load on the boom cylinder 44 (head pressure and bottom pressure; i.e., the pressure of the hydraulic oil supplied to the boom cylinder 44). The head pressure of the boom cylinder 44 is detected by the boom cylinder head pressure sensor 16. The bottom pressure of the boom cylinder 44 is detected by the boom cylinder bottom pressure sensor 15. The controller 10 calculates the moment Mboomcyl about the boom foot pin 47 generated by the load on the boom cylinder 44 based on the head pressure and bottom pressure of the boom cylinder 44.

[0038] Mboom is calculated by the product (r1×M1) of the distance r1 between the center of gravity C1 of the boom 41 and the boom foot pin 47 and the weight M1 of the boom 41. The position of the center of gravity C1 of the boom 41 is calculated from the boom angle A1, etc. The weight M1 of the boom 41, etc. are stored in the memory unit of the controller 10.

[0039] Marm is calculated by the product (r2×M2) of the distance r2 between the center of gravity C2 of the arm 42 and the boom foot pin 47 and the weight M2 of the arm 42. The position of the center of gravity C2 of the arm 42 is calculated from the arm angle A2, etc. The weight M2 of the arm 42, etc. are stored in the memory unit of the controller 10.

[0040] Mbucket is calculated by the product (r3×M3) of the distance r3 between the center of gravity C3 of the bucket 43 and the boom foot pin 47 and the weight M3 of the bucket 43. The position of the center of gravity C3 of the bucket 43 is calculated from the bucket angle A3 and the like. The weight M3 of the bucket 43 and the like are stored in the storage unit of the controller 10.

[0041] In calculating the current weight value W in the bucket 43, the controller 10 calculates the boom angle A1, the arm angle A2, and the bucket angle A3 based on the respective detection values ​​of the bucket IMU 11, the arm IMU 12, and the boom IMU 13. Based on these boom angle A1, arm angle A2, and bucket angle A3, the controller 10 calculates each position of the centers of gravity C1, C2, C3, and C4. The controller 10 calculates each distance r1, r2, and r3 between the centers of gravity C1, C2, and C3 and the boom foot pin 47.

[0042] The controller 10 reads out the weight M1 of the boom 41 from the storage unit, and calculates the product of the distance r1 and the weight M1 as the moment Mboom of the boom 41 about the boom foot pin 47. The controller 10 reads out the weight M2 of the arm 42 from the storage unit, and calculates the product of the distance r2 and the weight M2 as the moment Marm of the arm 42 about the boom foot pin 47. The controller 10 reads out the weight M3 of the bucket 43 from the storage unit, and calculates the product of the distance r3 and the weight M3 as the moment Mbucket of the bucket 43 about the boom foot pin 47.

[0043] The controller 10 reads out the length of the boom 41, the length of the arm 42, and the center of gravity C4 of the load in the bucket 43 at the rated load from the storage unit. The controller 10 calculates the horizontal distance L from the boom foot pin 47 to the center of gravity C4 of the load based on the boom angle A1, arm angle A2, and bucket angle A3 calculated above, the lengths of the boom 41 and arm 42, and the center of gravity C4 of the load.

[0044] The controller 10 substitutes the moments Mboomcyl, Mboom, Marm, Mbucket and distance L calculated as above into the above equation (1). In this way, the controller 10 calculates the weight value W of the current load loaded in the bucket 43. The weight value W of the load in the bucket 43 is calculated based on the load on the boom cylinder 44 and the attitude of the work machine 40.

[0045] The weight value W calculated as above may be unstable depending on the behavior of the vehicle body, and sufficient accuracy may not be obtained. In the embodiment, a range in which the behavior of the vehicle body is stable is extracted so that the weight value W can be calculated with high accuracy. Figure 4 is a flowchart showing a control method for a work machine in the embodiment.

[0046] 4, in step S1, the controller 10 calculates an instantaneous value of the weight value W of the load in the bucket 43 (hereinafter also referred to as the “payload”) in accordance with the above-mentioned equation (1). The calculation of the instantaneous value of the payload is always performed regardless of the operating status of the hydraulic excavator 50.

[0047] In step S2, the controller 10 calculates the standard deviation σp of the bottom pressure of the boom cylinder 44. The standard deviation is an example of an index that indicates the distance from an average value. The standard deviation is an index that indicates the degree of dispersion (variation) of numerical values ​​relative to the average. The standard deviation σp of the bottom pressure can be said to be an index that indicates the pressure fluctuation of the hydraulic oil supplied to the boom cylinder 44. The larger the standard deviation σp of the bottom pressure, the greater the variation.

[0048] The boom cylinder bottom pressure sensor 15 constantly detects the bottom pressure of the boom cylinder 44. The detection result of the bottom pressure of the boom cylinder 44 is constantly input from the boom cylinder bottom pressure sensor 15 to the controller 10. The controller 10 constantly calculates the standard deviation σp of the bottom pressure for a predetermined time going back from the current time. The predetermined time in this case may be, for example, a time corresponding to one cycle of fluctuations in the bottom pressure. The predetermined time may be the period from a peak to the next peak of the fluctuating bottom pressure. The predetermined time may be determined in advance and stored in the controller 10 in advance. The controller 10 may determine the predetermined time in real time.

[0049] The controller 10 may execute the calculation of the standard deviation σp of the bottom pressure while the hydraulic excavator 50 is executing hoist rotation. The controller 10 may start the calculation of the standard deviation σp of the bottom pressure when it is determined in the determination of step S3 that the hoist rotation is being executed.

[0050] In step S3, the controller 10 determines whether the hydraulic excavator 50 is performing hoist rotation in which the boom 41 rises while the rotating body 30 rotates. The controller 10 may determine whether hoist rotation is being performed based on the operation details of the left work implement lever 17 and the right work implement lever 18. The controller 10 may determine whether hoist rotation is being performed based on the detection results of the pressure of hydraulic oil supplied to the boom cylinder 44 and the rotation motor. The controller 10 may determine whether hoist rotation is being performed based on the detection results of the rotating body IMU 14 and the boom IMU 13.

[0051] If it is determined that hoist rotation is not being performed (NO in step S3), the determination in step S3 is repeated. Until hoist rotation is performed, the calculation of the average value of the payload is not performed, and the process is put on hold.

[0052] If it is determined that hoist rotation is being performed (YES in step S3), the process proceeds to step S4, where the controller 10 determines whether or not the standard deviation σp of the bottom pressure of the boom cylinder 44 is smaller than a threshold value. The threshold value of the standard deviation σp is pre-stored in the memory unit of the controller 10. The controller 10 reads out the threshold value from the memory unit. The controller 10 compares the standard deviation σp of the bottom pressure calculated in step S2 with the threshold value read out from the memory unit, and determines whether or not the standard deviation σp is smaller than the threshold value.

[0053] If it is determined that the standard deviation σp is smaller than the threshold value (YES in step S4), the process proceeds to step S5, where the controller 10 determines whether a certain time has elapsed since it was determined in step S3 that hoist rotation was being performed. The controller 10 has a timer that measures time. The controller 10 stores the time at which it was determined in step S3 that hoist rotation was being performed. The controller 10 reads the current time from the timer, and calculates the elapsed time from the time at which it was determined that hoist rotation was being performed to the current time. The controller 10 reads the threshold value of the elapsed time (the above-mentioned "certain time") from the storage unit. The controller 10 determines whether the elapsed time from the time at which it was determined that hoist rotation was being performed to the current time has reached the certain time.

[0054] If the certain time has not yet elapsed (NO in step S5), the process proceeds to step S6, where the controller 10 judges whether the standard deviation σp of the bottom pressure has changed from a value smaller than the threshold value to a value equal to or greater than the threshold value. The controller 10 compares the current standard deviation σp of the bottom pressure with the threshold value read from the storage unit, and judges whether the standard deviation σp is equal to or greater than the threshold value. If the standard deviation σp is smaller than the threshold value (NO in step S6), the controller 10 repeats the judgment in step S5 of whether the certain time has elapsed and the judgment in step S6 of whether the standard deviation σp is equal to or greater than the threshold value.

[0055] If it is determined that the standard deviation σp of the bottom pressure is equal to or greater than the threshold value before a certain period of time has elapsed (YES in step S6), the process proceeds to step S7, and the controller 10 resets the calculation of the payload. If it is determined in step S3 that hoist rotation is being performed, the controller 10 starts calculating the average value of the payload, and stops calculating the average value of the payload in step S7. The controller 10 returns the average value of the payload to the initial value (zero). The process returns to the determination of whether the standard deviation σp is smaller than the threshold value in step S4.

[0056] In the judgment of step S5, when it is judged that a certain time has passed and the state in which the standard deviation σp is smaller than the threshold value has continued for the certain time (YES in step S5), the controller 10 executes a judgment of whether or not to confirm the payload. In step S8, the controller 10 judges whether the standard deviation σp of the bottom pressure has become a value equal to or larger than the threshold value, whether a predetermined time has passed since it was judged in step S3 that the hoist rotation has started, or whether the bucket 43 has started a dump operation.

[0057] The controller 10 compares the current standard deviation σp of the bottom pressure with a threshold value read from the storage unit, and determines whether the standard deviation σp is equal to or greater than the threshold value.

[0058] The predetermined time is stored in the storage unit of the controller 10. The controller 10 stores the time at which it is determined in step S3 that hoist rotation is being performed. The controller 10 reads the current time from the timer and calculates the elapsed time from the time when hoist rotation was started to the current time. The controller 10 determines whether the elapsed time from the time when hoist rotation was started to the current time has reached the predetermined time.

[0059] The dump operation of the bucket 43 is an operation of lowering the blade tip of the bucket 43. When the bucket 43 performs the dump operation, a load inside the bucket 43 is discharged from the bucket 43. The controller 10 determines whether or not the operation of discharging a load from the bucket 43 has started.

[0060] The controller 10 may determine whether the bucket 43 has started the dumping operation based on the operation details of the right work implement lever 18. The controller 10 may determine whether the bucket 43 has started the dumping operation based on the detection result of the pressure of the hydraulic oil supplied to the bucket cylinder 46. The controller 10 may determine whether the bucket 43 has started the dumping operation based on the detection result of the bucket IMU 11.

[0061] If the standard deviation σp of the bottom pressure is smaller than the threshold value, a predetermined time has not yet elapsed since the start of hoist rotation, and the dump operation of the bucket 43 has not started (NO in step S8), the determination of whether or not to determine the payload in step S8 is repeated.

[0062] In the judgment in step S8, if it is determined that the standard deviation σp has reached a value equal to or greater than the threshold value, or if it is determined that the bucket 43 has started a dumping operation, or if it is determined that a predetermined time has elapsed since the start of hoist rotation (YES in step S8), processing proceeds to step S9.

[0063] In step S9, the controller 10 determines the average value of the payload during the period in which the standard deviation σp of the bottom pressure is smaller than the threshold value as the final value of the payload. As described in step S1, the calculation of the instantaneous value of the payload is performed continuously. The controller 10 determines the average value of the instantaneous values ​​of the payload calculated from the time when it is determined in step S4 that the standard deviation σp is smaller than the threshold value to the time when YES is determined in step S8 as the final value of the payload.

[0064] If it is determined in step S4 that the standard deviation σp of the bottom pressure is greater than or equal to the threshold value (NO in step S4), the processing proceeds to step S10, and the controller 10 determines whether the bucket 43 has started a dump operation or whether a predetermined time has elapsed since it was determined in step S3 that hoist rotation had started.

[0065] If the bucket 43 has not started the dump operation and the predetermined time has not yet elapsed since the start of hoist rotation (NO in step S10), the process returns to step S4, which is to determine whether or not the standard deviation σp is smaller than the threshold value.

[0066] In the judgment of step S10, when it is determined that the bucket 43 has started a dump operation or when it is determined that a predetermined time has elapsed since the start of hoist rotation (YES in step S10), the process proceeds to step S11. The controller 10 determines the average value of the payload during hoist rotation as the final payload value. As described in step S1, calculation of the instantaneous value of the payload is performed continuously. The controller 10 determines the final payload value as the average value of the instantaneous values ​​of the payload calculated from the time when it is determined in step S3 that hoist rotation has started to the time when YES is determined in step S10.

[0067] In this manner, the series of processes for calculating the weight value W of the load in the bucket 43 is completed ("END" in FIG. 4).

[0068] In the example shown in Fig. 4, if it is determined in step S5 that the state in which the standard deviation σp is smaller than the threshold has continued for a certain period of time, a determination is made in step S8 as to whether or not to determine the payload. The process of determining whether or not to determine the payload in step S8 does not necessarily have to be performed. If it is determined in step S5 that the certain period of time has elapsed, the process of determining the payload in step S9 may be performed subsequently.

[0069] In the example shown in Fig. 4, when it is determined in step S3 that hoist rotation is being performed, calculation of the average payload value is immediately started. A waiting time may be set when it is determined in step S3 that hoist rotation is being performed. A process flow may be such that the determination in step S4 is made after the waiting time has elapsed. The timing for starting calculation of the load weight may be delayed from the timing for starting hoist rotation.

[0070] In the example shown in Fig. 4, in step S3, it is determined whether or not hoist rotation is being performed in which the boom 41 is raised while the rotating body 30 is rotating. In addition to hoist rotation, even when the rotating body 30 is always just rotating, it is possible to accurately calculate the weight value W according to the process flow shown in Fig. 4.

[0071] FIG. 5 is a schematic diagram showing a first example of the timing of starting calculation of the payload average value and determining the payload average value. The horizontal axis of the graphs shown in FIG. 5 and the following FIGS. 6 to 11 is time, and the vertical axis of the graphs is the standard deviation σp of the bottom pressure of the boom cylinder 44. The dashed line extending parallel to the horizontal axis in the figure indicates the threshold value of the standard deviation σp. The white circle in the figure indicates the timing of starting calculation of the payload average value. The black circle in the figure indicates the timing of determining the payload. "Time X" described in the figure indicates the "predetermined time" described in step S8 of FIG. 4. "Time Y" described in the figure indicates the "fixed time" described in step S5 of FIG. 4.

[0072] In the example shown in Fig. 5, the standard deviation σp becomes smaller than the threshold value before the time when it is determined that hoist rotation is being performed. At the time when it is determined that hoist rotation is being performed, the standard deviation σp is smaller than the threshold value.

[0073] In Fig. 5, the state in which the standard deviation σp is smaller than the threshold continues for a certain period of time Y or more (YES in step S5 in Fig. 4), so a determination is made in step S8 as to whether or not to finalize the payload. The state in which the standard deviation σp is smaller than the threshold continues until the bucket 43 starts a dumping operation or a predetermined period of time X has elapsed since the start of hoist rotation. In this case, the controller 10 determines the average value of the instantaneous values ​​of the payload from the time when the hoist rotation starts until the time when the bucket 43 starts a dumping operation or a predetermined period of time X has elapsed since the start of hoist rotation as the final value of the payload (steps S8 and S9 in Fig. 4).

[0074] Fig. 6 is a schematic diagram showing a second example of the timing of starting calculation of the payload average value and determining the payload average value. In the example shown in Fig. 6, the standard deviation σp is larger than the threshold value when it is determined that hoist rotation is being performed. After the start of hoist rotation, the standard deviation σp changes from a value equal to or larger than the threshold value to a value smaller than the threshold value.

[0075] In Fig. 6, the state in which the standard deviation σp is smaller than the threshold continues for a certain period of time Y or more (YES in step S5 in Fig. 4), so a determination is made in step S8 as to whether or not to finalize the payload. The state in which the standard deviation σp is smaller than the threshold continues until the bucket 43 starts a dumping operation or a predetermined period of time X has elapsed since the start of hoist rotation. In this case, the controller 10 determines the finalized value of the payload to be the average value obtained by averaging the instantaneous values ​​of the payload from the point in time when the standard deviation σp becomes smaller than the threshold from a value equal to or greater than the threshold until the bucket 43 starts a dumping operation or the predetermined period of time X has elapsed since the start of hoist rotation (steps S8 and S9 in Fig. 4).

[0076] Fig. 7 is a schematic diagram showing a third example of the timing of starting calculation and determining the average payload value. In the example shown in Fig. 7, the standard deviation σp becomes smaller than the threshold value before the time when it is determined that hoist rotation is being performed. At the time when it is determined that hoist rotation is being performed, the standard deviation σp is smaller than the threshold value.

[0077] In Fig. 7, the state in which the standard deviation σp is smaller than the threshold continues for a certain time Y or more (YES in step S5 in Fig. 4), so a determination is made in step S8 as to whether or not to finalize the payload. The standard deviation σp changes from a value smaller than the threshold to a value equal to or greater than the threshold before the bucket 43 starts a dump operation or before a predetermined time X has elapsed since the start of hoist rotation. In this case, the controller 10 determines the average value of the instantaneous values ​​of the payload from the time when hoist rotation starts to the time when the standard deviation σp changes from a value smaller than the threshold to a value equal to or greater than the threshold as the final value of the payload (steps S8 and S9 in Fig. 4).

[0078] Fig. 8 is a schematic diagram showing a fourth example of the timing of starting calculation of the payload average value and determining the payload average value. In the example shown in Fig. 8, the standard deviation σp is larger than the threshold value when it is determined that hoist rotation is being performed. After the start of hoist rotation, the standard deviation σp changes from a value equal to or larger than the threshold value to a value smaller than the threshold value.

[0079] In Fig. 8, the state in which the standard deviation σp is smaller than the threshold continues for a certain time Y or more (YES in step S5 in Fig. 4), so a determination is made in step S8 as to whether or not to finalize the payload. The standard deviation σp changes from a value smaller than the threshold to a value equal to or greater than the threshold before the bucket 43 starts a dumping operation or before a predetermined time X has elapsed since the start of hoist rotation. In this case, the controller 10 determines the average value of the instantaneous values ​​of the payload from the point in time when the standard deviation σp changes from a value equal to or greater than the threshold to the point in time when the standard deviation σp changes from a value smaller than the threshold to a value equal to or greater than the threshold as the final value of the payload (steps S8 and S9 in Fig. 4).

[0080] Fig. 9 is a schematic diagram showing a fifth example of the timing of starting and determining the payload average value calculation. In the example shown in Fig. 9, the standard deviation σp is larger than the threshold value when it is determined that hoist rotation is being performed. After hoist rotation starts, the standard deviation σp changes from a value equal to or larger than the threshold value to a value smaller than the threshold value, but before the fixed time Y has elapsed, the standard deviation σp becomes equal to or larger than the threshold value. In this case, the calculation of the payload average value is reset (steps S4 to S7 in Fig. 4).

[0081] In Fig. 9, the state in which the standard deviation σp is smaller than the threshold continues for a certain time Y or more (YES in step S5 in Fig. 4), so a determination is made in step S8 as to whether or not to finalize the payload. The standard deviation σp changes from a value smaller than the threshold to a value equal to or greater than the threshold before the bucket 43 starts a dumping operation or before a predetermined time X has elapsed since the start of hoist rotation. In this case, the controller 10 determines the average value of the instantaneous values ​​of the payload from the point in time when the standard deviation σp changes from a value equal to or greater than the threshold back to a value smaller than the threshold to the point in time when the standard deviation σp changes from a value smaller than the threshold to a value equal to or greater than the threshold as the final value of the payload (steps S8 and S9 in Fig. 4).

[0082] FIG. 10 is a schematic diagram showing a sixth example of the timing of starting calculation of the payload average value and determining the payload average value. In the example shown in FIG. 10, the standard deviation σp is larger than the threshold value at the time when it is determined that hoist rotation is being performed. After hoisting is started, the standard deviation σp does not become smaller than the threshold value until the bucket 43 starts dumping operation or a predetermined time X has elapsed since the start of hoist rotation (NO in step 4 of FIG. 4). In this case, the controller 10 determines the average value of the payload during hoist rotation as the determined value of the payload. The controller 10 determines the average value of the instantaneous values ​​of the payload from the time when hoist rotation is started to the time when the bucket 43 starts dumping operation or a predetermined time X has elapsed since the start of hoist rotation as the determined value of the payload (steps S10 and S11 of FIG. 4).

[0083] Fig. 11 is a schematic diagram showing a seventh example of the timing of starting and determining the calculation of the payload average value. In the example shown in Fig. 11, at the time when it is determined that hoist rotation is being performed, the standard deviation σp is larger than the threshold value. After hoist rotation starts, the standard deviation σp changes from a value equal to or larger than the threshold value to a value smaller than the threshold value, but before the fixed time Y has elapsed, the standard deviation σp becomes equal to or larger than the threshold value. In this case, the calculation of the payload average value is reset (steps S4 to S7 in Fig. 4).

[0084] In Fig. 11, from the start of hoist rotation until the bucket 43 starts dumping operation or a predetermined time X has elapsed since the start of hoist rotation, the state in which the standard deviation σp is smaller than the threshold value does not continue for a certain time Y or more. In this case, the controller 10 sets the average value of the payload during hoist rotation as the final value of the payload. The controller 10 sets the average value of the instantaneous values ​​of the payload from the start of hoist rotation until the bucket 43 starts dumping operation or a predetermined time X has elapsed since the start of hoist rotation as the final value of the payload (steps S10 and S11 in Fig. 4).

[0085] <Action and Effects> Although some of the description herein overlaps with the above description, the characteristic configuration and effects of this embodiment can be summarized as follows.

[0086] As shown in Fig. 3, the controller 10 calculates the weight of the load carried by the work implement 40 based on the pressure of the hydraulic oil supplied to the boom cylinder 44. As shown in Figs. 4 to 9, the controller 10 calculates the weight of the load carried by the work implement 40 when the pressure fluctuation of the hydraulic oil supplied to the boom cylinder 44 is smaller than a specified value.

[0087] The pressure of the hydraulic oil supplied to the boom cylinder 44 has a large effect on the weight of the load carried by the work implement 40. Focusing on the pressure fluctuation of the hydraulic oil, the standard deviation σp is used as an index of pressure variation. If the variation in hydraulic pressure is small, the variation in the calculated value of the load weight is also small, so the load weight can be calculated stably. By calculating the load weight when the hydraulic oil pressure is stable, the weight of the load carried by the work implement 40 can be calculated with high accuracy.

[0088] 4, the controller 10 may constantly calculate the instantaneous value of the load weight and calculate the weight of the load by averaging the instantaneous values. By calculating the weight of the load as an average value that smooths out the temporal variation of the instantaneous weight values, the weight of the load can be calculated more accurately.

[0089] 4 to 9, the controller 10 may determine whether to determine the weight of the load when the pressure fluctuation of the hydraulic oil remains smaller than a specified value for a certain period of time. In this way, the weight of the load can be determined when the pressure of the hydraulic oil is stable.

[0090] As shown in Figs. 4 and 9, the controller 10 may reset the calculation of the load weight if the pressure fluctuation of the hydraulic oil becomes equal to or greater than a specified value before a certain period of time has elapsed. If the pressure fluctuation of the hydraulic oil becomes smaller than the specified value and then becomes equal to or greater than the specified value in a short period of time, the load weight calculated up to that point is not used. When the pressure fluctuation of the hydraulic oil becomes smaller than the specified value again, the calculation of the load weight is restarted. An unstable calculation result from a short period of time is not determined as the load weight. In this manner, the load weight can be calculated reliably and accurately.

[0091] 4, and 7 to 9, the controller 10 may determine the weight of the load when the pressure fluctuation of the hydraulic oil changes from a value smaller than a specified value to a value equal to or larger than the specified value. By calculating the weight of the load when the pressure fluctuation of the hydraulic oil is smaller than the specified value and determining the weight of the load when the pressure fluctuation of the hydraulic oil increases to a value equal to or larger than the specified value, the weight of the load can be calculated with high accuracy when the pressure of the hydraulic oil is stable.

[0092] 4, 6, 8-9, the controller 10 may start calculating the weight of the load when the pressure fluctuation of the hydraulic oil becomes smaller than the specified value from a value equal to or larger than the specified value. In this way, it is possible to reliably calculate the weight of the load when the pressure of the hydraulic oil is stable.

[0093] 4 to 11, the controller 10 may calculate the weight of the load during hoist rotation in which the rotating body 30 rotates and the work machine 40 rises. By calculating the weight of the load during hoist rotation from the time when the hydraulic excavator 50 completes excavation to scoop up the load into the bucket 43 until the time when the load is unloaded onto a loading machine such as a dump truck, the weight of the load can be calculated with high accuracy.

[0094] 4 to 5 and 7, the controller 10 may start calculating the weight of the load when starting hoist rotation. In this way, it becomes possible to reliably calculate the weight of the load during hoist rotation.

[0095] 4 to 11, the controller 10 may determine the weight of the load when a predetermined time has elapsed since the start of hoist rotation. By setting the timing for determining the weight of the load in this manner, the weight of the load can be determined early and the weight of the load can be calculated in a short time.

[0096] 4 to 11, the controller 10 may determine the weight of the load in the bucket 43 when starting the operation of unloading the load from the bucket 43. When the load starts to be unloaded from the bucket 43, the weight of the load in the bucket 43 fluctuates. By determining the weight of the load in the bucket 43 for the period until the load is unloaded from the bucket 43, excluding the time period in which the weight of the load fluctuates, the weight of the load can be calculated with higher accuracy.

[0097] In the embodiment, an example has been described in which the hydraulic excavator 50 is equipped with the bucket 43 as an attachment at the tip of the work implement 40, and the weight of the load in the bucket 43 is calculated. The attachment is not limited to the bucket 43, and other types of attachments may be attached to the tip of the work implement 40 depending on the type of work. For example, the attachment may be a lifting magnet, and in this case, the load carried by the work implement 40 may be a magnetic body that is attracted to and held by the lifting magnet.

[0098] In the embodiment, an example has been described in which the work machine is the hydraulic excavator 50. The work machine is not limited to the hydraulic excavator 50, and may be another type of work machine having a work implement capable of transporting a load and a hydraulic cylinder for operating the work implement. For example, the work machine may be a loading shovel, a tire-type shovel, a wheel loader, a skid steer loader, or the like.

[0099] <Additional Notes> The above description includes the following additional features.

[0100] (Appendix 1) A working machine, a hydraulic cylinder that operates the working machine using hydraulic oil; a controller that calculates a weight of a load carried by the work machine based on the pressure of the hydraulic oil supplied to the hydraulic cylinder when pressure fluctuation of the hydraulic oil supplied to the hydraulic cylinder is smaller than a specified value.

[0101] (Appendix 2) 2. The work machine of claim 1, wherein the controller constantly calculates an instantaneous value of the weight and calculates the weight by averaging the instantaneous values.

[0102] (Appendix 3) The working machine according to claim 1 or 2, wherein the controller determines whether to confirm the weight when a state in which the pressure variation is smaller than the specified value continues for a certain period of time.

[0103] (Appendix 4) The work machine according to claim 3, wherein the controller resets the calculation of the weight if the pressure variation becomes equal to or greater than the specified value before the fixed time period has elapsed.

[0104] (Appendix 5) 5. The work machine according to any one of claims 1 to 4, wherein the controller determines the weight when the pressure variation changes from a value smaller than the specified value to a value equal to or greater than the specified value.

[0105] (Appendix 6) The work machine according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the controller starts calculating the weight when the pressure variation changes from a value equal to or greater than the specified value to a value smaller than the specified value.

[0106] (Appendix 7) A rotating body that rotates around a rotation center and supports the working machine is further provided. 7. The work machine according to any one of Supplementary Note 1 to Supplementary Note 6, wherein the controller calculates the weight during hoist rotation in which the rotating body rotates and the work machine is raised.

[0107] (Appendix 8) The work machine of claim 7, wherein the controller starts calculating the weight when the hoist rotation starts.

[0108] (Appendix 9) 9. The work machine of claim 7 or 8, wherein the controller determines the weight when a predetermined time has elapsed from the start of the hoist rotation.

[0109] (Appendix 10) The work machine has a bucket at a tip, 10. The work machine of any one of claims 1 to 9, wherein the controller determines the weight of the load in the bucket when commencing an operation to unload the load from the bucket. EXAMPLES

[0110] An example will be described below. Fig. 12 is a diagram showing the accuracy of payload calculation in an example and a comparative example. The horizontal axis of the three graphs shown in Fig. 12 is time. The vertical axis of the upper graph is the instantaneous value of the payload. The vertical axis of the middle graph is the average value of the payload. The vertical axis of the lower graph is the standard deviation σp of the bottom pressure of the boom cylinder 44.

[0111] As explained in steps S1 and S2 of Fig. 4, the calculation of the instantaneous value of the payload and the calculation of the standard deviation σp of the hydraulic pressure are always performed. As shown in Fig. 12, the calculation of the instantaneous value of the payload and the calculation of the standard deviation σp of the hydraulic pressure are performed before the hydraulic excavator 50 starts hoist rotation, and the calculation of the instantaneous value of the payload and the calculation of the standard deviation σp of the hydraulic pressure are also performed when the bucket 43 starts a dumping operation or a predetermined time X has elapsed since the start of hoist rotation.

[0112] In the embodiment, the average value obtained by averaging the instantaneous values ​​of the weight of the load carried by the work implement 40 during a period in which the pressure fluctuation of the hydraulic oil supplied to the boom cylinder 44 is smaller than a specified value is calculated as the final value of the payload, according to the flowchart shown in Fig. 4. In the comparative example, the average value obtained by averaging the instantaneous values ​​of the weight of the load from the time when hoist rotation starts until the time when the bucket 43 starts the dumping operation or a predetermined time X has elapsed since the start of hoist rotation is calculated as the final value of the payload. The white and black circles in Fig. 12 indicate the timing for starting calculation of the average value of the payload and the timing for determining the payload, respectively, as in Figs. 5 to 11.

[0113] As shown in Fig. 12, the difference between the determined value and the true value of the payload was smaller in the working example and larger in the comparative example. In the time period immediately before the bucket 43 starts the dumping operation or the time when the predetermined time X has elapsed since the start of the hoist rotation, the standard deviation σp of the hydraulic pressure exceeds the threshold value, and the calculated instantaneous value of the payload decreases. In the comparative example, the average value of the payload was calculated including this time period, resulting in a large error. In contrast, in the working example, the average value of the payload is calculated only during the time period when the standard deviation σp of the hydraulic pressure is stable, excluding the above time period, thereby making it possible to reduce the error and calculate the payload with greater accuracy.

[0114] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0115] 10 controller, 11 bucket IMU, 12 arm IMU, 13 boom IMU, 14 rotating body IMU, 15 boom cylinder bottom pressure sensor, 16 boom cylinder head pressure sensor, 17 left work implement lever, 18 right work implement lever, 30 rotating body, 31 operator's cab, 35 traveling body, 40 work implement, 41 boom, 42 arm, 43 bucket, 44 boom cylinder, 45 arm cylinder, 46 bucket cylinder, 47 boom foot pin, 48 boom tip pin, 49 arm tip pin, 50 hydraulic excavator.

Claims

1. A working machine, a hydraulic cylinder that operates the working machine using hydraulic oil; a controller that calculates a weight of a load carried by the work machine based on the pressure of the hydraulic oil supplied to the hydraulic cylinder when a pressure fluctuation of the hydraulic oil supplied to the hydraulic cylinder is smaller than a specified value.

2. The work machine according to claim 1 , wherein the controller constantly calculates an instantaneous value of the weight and calculates the weight by averaging the instantaneous values.

3. 2. The work machine according to claim 1, wherein the controller determines whether or not to confirm the weight when a state in which the pressure fluctuation is smaller than the specified value continues for a certain period of time.

4. The work machine according to claim 3 , wherein the controller resets the calculation of the weight if the pressure variation becomes equal to or greater than the specified value before the fixed time period has elapsed.

5. The work machine according to claim 1 , wherein the controller determines the weight when the pressure fluctuation changes from a value smaller than the specified value to a value equal to or greater than the specified value.

6. The work machine according to claim 1 , wherein the controller starts calculating the weight when the pressure variation changes from a value equal to or greater than the specified value to a value smaller than the specified value.

7. A rotating body that rotates around a rotation center and supports the working machine is further provided. The work machine according to claim 1 , wherein the controller calculates the weight during a hoist rotation in which the rotating body rotates and the work implement is raised.

8. The work machine of claim 7 , wherein the controller initiates the calculation of the weight when the hoist swing is initiated.

9. The work machine of claim 7 , wherein the controller determines the weight when a predetermined time has elapsed from the start of the hoist swing.

10. The work machine has a bucket at a tip, The work machine of claim 1 , wherein the controller determines the weight of the load in the bucket when initiating an operation to empty the load from the bucket.

11. Detecting a pressure of hydraulic oil supplied to a hydraulic cylinder that operates a work machine; Calculating the pressure fluctuation of the hydraulic oil; calculating a weight of a load carried by the work machine based on the pressure of the hydraulic oil supplied to the hydraulic cylinder when the pressure fluctuation is smaller than a specified value.

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