Work machine, system including work machine, and control method for work machine

Abstract

To provide a work machine having improved relation accuracy between the mass of load in a bucket and the posture of the bucket.SOLUTION: A work machine includes machinery having a bucket at the tip, and a controller that commands operations of the machinery. The controller modifies pre-memorized relations based on the pre-memorized relations between the mass of a load in the bucket and the posture of the bucket, and an acquired load mass in one specific bucket posture.SELECTED DRAWING: Figure 12

Description

[Technical Field]

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

[0002] Tipping off is the act of dropping excess material from a bucket. Tipping off is performed, for example, to adjust the amount of material being loaded from a work machine to a transport machine. U.S. Patent Application Publication No. 2022 / 0325497 (Patent Document 1) describes an automatic tipping off process with agitation. Different agitation patterns are selected depending on the type of material being handled. Machine learning can be used to model the amount of material spilled during a bucket dump based on characteristics of the tipping off process, including the agitation pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2022 / 0325497 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to prevent overloading of a conveyance machine traveling on a predetermined travel path, it is required to be able to accurately determine the mass of the load in the bucket in a given bucket posture.

[0005] The present disclosure proposes a work machine, a system including a work machine, and a method for controlling a work machine that can improve the accuracy of the relationship between the load mass in a bucket and the attitude of the bucket. [Means for solving the problem]

[0006] A work machine according to one aspect of the present disclosure includes a work implement having a bucket at its tip and a controller that commands the operation of the work implement. The controller modifies the pre-stored relationship between the load mass (the mass of the load in the bucket) and the bucket attitude based on the acquired load mass at one specific bucket attitude.

[0007] A work machine according to one aspect of the present disclosure includes a work implement having a bucket at its tip, and a controller that commands the operation of the work implement. The controller selectively performs one of the following: modifying a pre-stored relationship between a load mass (the mass of a load in the bucket) and the bucket attitude based on the load mass at one specific bucket attitude that has been acquired; or, after maximizing the load mass, discharging the load from the bucket and acquiring the load mass and bucket attitude during the discharge of the load, modifying the pre-stored relationship.

[0008] A system according to one aspect of the present disclosure includes a work machine. The work machine includes a work implement having a bucket at its tip. The system also includes a controller that commands operation of the work implement. The controller modifies the pre-stored relationship between a load mass, which is the mass of a load in the bucket, and the bucket attitude based on the load mass at one acquired specific bucket attitude.

[0009] A control method for a work machine according to one aspect of the present disclosure includes the following steps. A first step is to set a bucket at the tip of the work machine to one specific attitude. A second step is to obtain a load mass, which is the mass of a load in the bucket when the bucket is in the specific attitude. A third step is to modify a pre-stored relationship between the load mass and the attitude of the bucket based on the obtained load mass. [Effects of the Invention]

[0010] According to the present disclosure, the accuracy of the relationship between the load mass in the bucket and the attitude of the bucket can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a side view of a wheel loader. [Figure 2] FIG. 2 is a diagram for explaining the dimensions of each part of the work machine and the balance of four moments. [Figure 3] FIG. 10 is a schematic diagram illustrating tip-off after excavation work by a wheel loader. [Figure 4] FIG. 2 is a functional block diagram showing the functional configuration of the wheel loader. [Figure 5] FIG. 10 is a flowchart illustrating the flow of processing for auto tip-off control. [Figure 6] FIG. 10 is a flow chart showing the flow of a process for calculating a target soil volume. [Figure 7] FIG. 4 is a schematic diagram showing the process of dump control. [Figure 8] FIG. 10 is a flowchart illustrating the flow of a normal calibration process. [Figure 9] FIG. 10 is a schematic diagram of a screen displayed on the display unit during normal calibration. [Figure 10] FIG. 10 is a flowchart illustrating the flow of a simple calibration process. [Figure 11] FIG. 10 is a diagram illustrating an example of a stored default table. [Figure 12] FIG. 10 shows an example of a table modification for a first material. [Figure 13] FIG. 10 shows an example of a table modification for a second material. [Figure 14] FIG. 10 is a diagram illustrating an example of table modification when a bucket is changed. [Figure 15] FIG. 10 is a diagram showing an example of table correction when the angle of repose of a material is changed. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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 descriptions thereof will not be repeated. In the drawings, configurations may be omitted or simplified for the sake of convenience. It is also intended from the beginning that any configurations may be extracted from the embodiments and arbitrarily combined.

[0013] <Work machine configuration> As an example of a work machine according to an embodiment, the configuration of a wheel loader 1 will be described using Figure 1. The work machine according to the embodiment is not limited to the wheel loader 1. The work machine may be any work machine equipped with a work implement having a bucket at the tip, and may be a backhoe, a loading shovel, or the like.

[0014] Figure 1 is a side view of a wheel loader 1 as an example of a work machine according to an embodiment. As shown in Figure 1, the wheel loader 1 has a body frame 2, a work implement 3, a traveling device 4, and a cab 5. The wheel loader 1 further has a controller 50 (Figure 4) that commands the operation of the work implement 3, which will be described later.

[0015] The vehicle frame 2 and cab 5 make up the vehicle body (machine body 9) of the wheel loader 1. Inside the cab 5, there are arranged a seat for the operator, operation devices, a monitor, etc. The operation devices include an operation lever for traveling (forward and backward), an operation lever for the work implement 3, an input device, etc. The work implement 3 and traveling device 4 are attached to the machine body 9 of the wheel loader 1. The work implement 3 is arranged in front of the machine body 9, and a counterweight 6 is attached to the rearmost end of the machine body 9.

[0016] The vehicle body frame 2 includes a front frame 11 and a rear frame 12. A steering cylinder 13 is attached to the front frame 11 and the rear frame 12. The steering cylinder 13 is a hydraulic cylinder. The steering cylinder 13 expands and contracts using hydraulic oil from a steering pump (not shown). The expansion and contraction of the steering cylinder 13 allows the front frame 11 and the rear frame 12 to swing left and right relative to each other. This allows the traveling direction of the wheel loader 1 to be changed left and right.

[0017] In this specification, the direction in which the wheel loader 1 travels straight ahead is referred to as the fore-and-aft direction of the wheel loader 1. In the fore-and-aft direction of the wheel loader 1, the side on which the work implement 3 is arranged relative to the body frame 2 is referred to as the front direction, and the side opposite the front direction is referred to as the rear direction. The left-and-right direction of the wheel loader 1 is the direction perpendicular to the fore-and-aft direction in a plan view. Looking forward, the right and left sides of the left-and-right direction are the right direction and the left direction, respectively. The up-and-down direction of the wheel loader 1 is the direction perpendicular to the plane defined by the fore-and-aft direction and the left-and-right direction. In the up-and-down direction, the side with the ground facing is the bottom side, and the side with the sky facing is the top side.

[0018] The traveling device 4 includes traveling wheels 4a, 4b. Each of the traveling wheels 4a, 4b is a wheel and has a tire made of rubber. The traveling wheel (front wheel) 4a is rotatably attached to the front frame 11. The traveling wheel (rear wheel) 4b is rotatably attached to the rear frame 12. The wheel loader 1 can be self-propelled by the traveling wheels 4a, 4b being rotationally driven.

[0019] The work implement 3 is used to perform work such as excavation. The work implement 3 is attached to a front frame 11. The work implement 3 includes a bucket 14, a boom 15, a bell crank 16, and a tilt rod 17.

[0020] The base end of the boom 15 is rotatably attached to the front frame 11 by a boom foot pin 21. This rotatably attaches the boom 15 to the machine body 9. The bucket 14 is rotatably attached to the tip of the boom 15 by a bucket pin 22. The bucket 14 is disposed at the tip of the work implement 3. The work implement 3 has the bucket 14 at its tip. The bucket 14 is a work tool used for excavation and loading. The cutting edge 14a is the tip of the bucket 14. The back surface 14b is part of the outer surface of the bucket 14 that extends rearward from the cutting edge 14a. The back surface 14b is formed as a flat surface.

[0021] The boom cylinder 18 drives the boom 15. One end of the boom cylinder 18 is rotatably attached to the front frame 11 of the machine body 9 by a pin 23. This allows the boom cylinder 18 to be rotatably attached to the machine body 9. The other end of the boom cylinder 18 is rotatably attached to the boom 15 by a pin 24.

[0022] The boom cylinder 18 is, for example, a hydraulic cylinder. The boom cylinder 18 expands and contracts using hydraulic oil from a work equipment pump (not shown). This drives the boom 15, and the bucket 14 attached to the tip of the boom 15 moves up and down.

[0023] The boom cylinder 18 is attached to the machine body 9 through a tube 18a (cylinder tube) and the boom 15. The boom cylinder 18 is attached to the tube 18a through a thrust F of the boom cylinder 18. cyl The boom cylinder 18 has a rod 18b (piston rod) that is moved by hydraulic pressure (see FIG. 2). The rod 18b has a piston 18c. The piston 18c moves within the tube 18a due to hydraulic pressure, thereby changing the stroke length of the boom cylinder 18.

[0024] Bell crank 16 is rotatably supported on boom 15 by a support pin 29. Bell crank 16 has a first end located on one side of support pin 29 and a second end located on the opposite side of support pin 29 from the first end. The first end of bell crank 16 is connected to bucket 14 via tilt rod 17. The second end of bell crank 16 is connected to front frame 11 of machine body 9 via bucket cylinder 19.

[0025] One end of tilt rod 17 is rotatably attached to a first end of bell crank 16 by a pin 27. The other end of tilt rod 17 is rotatably attached to bucket 14 by a pin 28.

[0026] The bucket cylinder 19 drives the bucket 14 relative to the boom 15. The bucket cylinder 19 has one end and another end opposite the one end. One end of the bucket cylinder 19 is rotatably attached to the front frame 11 of the machine body 9 by a pin 25. The other end of the bucket cylinder 19 is rotatably attached to the second end of the bell crank 16 by a pin 26.

[0027] The bucket cylinder 19 is, for example, a hydraulic cylinder. The bucket cylinder 19 expands and contracts using hydraulic oil from a work equipment pump (not shown). This drives the bucket 14, which rotates up and down relative to the boom 15 around a bucket pin 22. The bucket cylinder 19 generates a driving force that moves the bucket 14 relative to the boom 15, with the tip of the boom 15 serving as a fulcrum. The direction in which the cutting edge 14a of the bucket 14 rises (moves upward) is called the tilt direction. The direction in which the cutting edge 14a of the bucket 14 lowers (moves downward) is called the dump direction.

[0028] The wheel loader 1 is driven by the thrust F of the boom cylinder 18. cyl The thrust force is defined as a force that pushes an object in the direction of movement, and the thrust force F of the boom cylinder 18 iscyl is a thrust generated by the boom cylinder 18 that rotates the boom 15 relative to the vehicle body. The thrust of the bucket cylinder 19 is a thrust generated by the bucket cylinder 19 that rotates the bucket 14 relative to the boom 15.

[0029] The sensors that detect information related to the thrust of the boom cylinder 18 are, for example, pressure sensors 31b and 31h. Each of the pressure sensors 31b and 31h detects the cylinder pressure of the boom cylinder 18. The pressure sensor 31b detects the bottom pressure of the boom cylinder 18. The pressure sensor 31h detects the head pressure of the boom cylinder 18.

[0030] The head pressure means the pressure on the cylinder rod side relative to the piston of the hydraulic cylinder, and the bottom pressure means the pressure on the tube side relative to the piston.

[0031] The sensors that detect information related to the thrust of the bucket cylinder 19 are, for example, pressure sensors 32b and 32h. Each of the pressure sensors 32b and 32h detects the cylinder pressure of the bucket cylinder 19. The pressure sensor 32b detects the bottom pressure of the bucket cylinder 19. The pressure sensor 32h detects the head pressure of the bucket cylinder 19.

[0032] The wheel loader 1 further includes a sensor that detects information relating to the attitude of the work implement 3. The sensor that detects information relating to the attitude of the work implement 3 includes, for example, a sensor that detects information relating to the boom angle and a sensor that detects information relating to the bucket ground angle θ B The information relating to the attitude of the work implement 3 will be described in detail later (FIG. 2).

[0033] The boom angle is the angle of the boom 15 relative to the front frame 11 of the machine body 9. More specifically, the boom angle is the angle formed between the boom 15 and an imaginary axis extending in the fore-and-aft direction of the vehicle body in a side view of the wheel loader 1 (FIG. 1) (more specifically, an axis that is horizontal when the ground G on which the wheel loader 1 travels is horizontal). The boom reference line P shown in FIG. 1 is a line that passes through the center of the boom foot pin 21 and the center of the bucket pin 22. The boom angle is the angle formed between the boom reference line P and a horizontal line extending forward from the center of the boom foot pin 21.

[0034] The sensor that detects information related to the boom angle is, for example, a potentiometer 33. The potentiometer 33 is attached so as to be concentric with the boom foot pin 21. Instead of the potentiometer 33, a stroke sensor 35 of the boom cylinder 18 may be used as the sensor that detects information related to the boom angle.

[0035] An IMU (Inertial Measurement Unit) 37 or an imaging device (e.g., a camera) 39 may be used as a sensor for detecting information related to the boom angle. The IMU 37 is attached to, for example, the boom 15. The imaging device 39 is attached to the machine body 9 (e.g., the cab 5).

[0036] The bell crank reference line Q shown in FIG. 1 is a line passing through the center of the support pin 29 and the center of the pin 26. The bell crank angle θ2 is the angle between the boom reference line P and the bell crank reference line Q. The bucket ground angle θ B is the angle of the bucket 14 with respect to the ground G. The bucket back surface extension line E shown in FIG. 1 is a straight line extending the back surface 14b of the bucket 14 when viewed from the side. Bucket ground angle θ B is the angle between the ground G and the extension line E of the back surface of the bucket. By detecting the bell crank angle θ2, the bucket ground angle θ B When the back surface 14b of the bucket 14 is in a position parallel to the ground G, the bucket ground angle θ BWhen the bucket 14 is moved in the tilt direction, the bucket ground angle θ B When the bucket 14 is moved in the dump direction, the bucket ground angle θ B is taken as negative.

[0037] Bucket ground angle θ B The sensor that detects the information about the bucket angle θ is, for example, a potentiometer 34. The potentiometer 34 is attached so as to be concentric with the support pin 29. B As a sensor for detecting information relating to the above, a stroke sensor 36 of the bucket cylinder 19 may be used instead of the potentiometer 34.

[0038] Bucket ground angle θ B The IMU 38 or the imaging device 39 may be used as a sensor for detecting information relating to the tilt rod 17. The IMU 38 is attached to the tilt rod 17, for example.

[0039] The potentiometers 33, 34, stroke sensors 35, 36, IMUs 37, 38, and imaging device 39 may be used as sensors that detect information related to the position of the center of gravity GC1 of the work implement 3. The potentiometers 33, 34, stroke sensors 35, 36, IMUs 37, 38, and imaging device 39 may be used as sensors that detect information related to the position of the center of gravity GC2 of the load in the bucket 14.

[0040] The wheel loader 1 may further include an angle sensor 40. The angle sensor 40 detects the tilt angle (pitch angle) of the machine body 9 with respect to a direction perpendicular to the direction of gravity, which serves as a reference (horizontal plane). For example, an IMU attached to the machine body 9 may be used as this angle sensor 40. The angle sensor 40 may be attached to any of the front frame 11, rear frame 12, and cab 5, as long as it is attached to the machine body 9.

[0041] <Calculating cargo mass> FIG. 2 is a diagram for explaining the dimensions of each part of the work machine 3 and the balance of four moments.

[0042] The above-mentioned "information related to the posture of the work implement 3" refers to the dimensions Rl2 and Rb5 shown in Fig. 2. The dimension Rl2 is the dimension between the boom foot pin 21 and the pin 23, and is the dimension in the direction perpendicular to the extension direction of the boom cylinder 18. The dimension Rb5 is the dimension between the boom foot pin 21 and the pin 26, and is the dimension in the direction perpendicular to the extension direction of the bucket cylinder 19.

[0043] The above-mentioned "information relating to the position of the center of gravity GC1 of the work implement 3" is the dimension RI3. The dimension RI3 is the dimension between the center of gravity GC1 and the boom foot pin 21, and is the dimension along the front-to-rear direction of the wheel loader 1. When the ground G (FIG. 1) on which the wheel loader 1 is placed is horizontal, the dimension RI3 is the dimension along the horizontal direction between the center of gravity GC1 and the boom foot pin 21.

[0044] The above-mentioned "information relating to the position of the center of gravity GC2 of the load in the bucket 14" is the dimension Rl1. The dimension Rl1 is the dimension between the center of gravity GC2 and the boom foot pin 21, and is the dimension along the fore-and-aft direction of the wheel loader 1. When the ground G on which the wheel loader 1 is placed is horizontal, the dimension Rl1 is the dimension along the horizontal direction between the center of gravity GC2 and the boom foot pin 21.

[0045] The dimension Rb1 is the dimension between the center of gravity GC2 of the load and the pin 22, and is the dimension along the front-to-rear direction of the wheel loader 1. When the ground G on which the wheel loader 1 is placed is horizontal, the dimension Rb1 is the dimension along the horizontal direction between the center of gravity GC2 of the load and the pin 22.

[0046] Dimension Rb2 is the dimension between pin 22 and pin 27, and is the dimension in the direction perpendicular to the extension direction of tilt rod 17. Dimension Rb3 is the dimension between pin 27 and support pin 29, and is the dimension in the direction perpendicular to the extension direction of tilt rod 17. Dimension Rb4 is the dimension between pin 26 and support pin 29, and is the dimension in the direction perpendicular to the extension direction of bucket cylinder 19.

[0047] The dimension Rb6 is the dimension between the center of gravity GC3 of the bucket 14 and the pin 22, and is the dimension along the front-to-rear direction of the wheel loader 1. When the ground G on which the wheel loader 1 is placed is horizontal, the dimension Rb6 is the dimension along the horizontal direction between the center of gravity GC3 of the bucket 14 and the pin 22.

[0048] The values ​​of Rli (i=1 to 3) and Rbj (j=1 to 6) are calculated by the controller 50 (FIG. 4) based on the design dimensions of each member constituting the work implement 3, the boom angle, and the bell crank angle θ2.

[0049] In the following, the balance of the four moments is used to calculate the load mass W, which is the mass of the excavation target scooped into the bucket 14 during the excavation work. load Referring to Figure 2, calculate the moment a due to the weight F1 of the cargo. Wload is expressed by the following equation (1).

[0050]

number

[0051] In equation (1), g is the acceleration due to gravity. The same applies to equations (2) and (4) described below.

[0052] Moment b due to weight F2 of work equipment 3 Wload is calculated by multiplying the weight F2 of the work machine 3 by R13 (Fig. 2). Wload is expressed by the following equation (2).

[0053]

number

[0054] Total mass of work equipment 3 W we is the sum of the masses of the bucket 14, boom 15, bell crank 16, and tilt rod 17 that constitute the work implement 3.

[0055] Boom cylinder 18 thrust F cyl Moment c by Wload is expressed by the following equation (3).

[0056]

number

[0057] In equation (3), η is the hydraulic transmission efficiency of the boom 15.

[0058] Moment d due to reaction force F4 of bucket 14 Wload is expressed by the following equation (4).

[0059]

number

[0060] In equation (4), Wg bucket is the mass of the bucket 14. β is an empty load correction coefficient. β is a coefficient for correcting the empty load state when buckets 14 of different masses are attached to the boom 15.

[0061] Moment a due to the weight of the load F1 Wload and moment b due to the weight F2 of the work machine 3 Wload and the thrust F of the boom cylinder 18 cyl Moment c by Wload and moment d due to reaction force F4 of bucket 14 Wload The following equation (5) shows the equilibrium relationship between the two.

[0062]

number

[0063] From equation (5), the cargo mass W load The result is the following equation (6): load is included in equations (1) and (4).

[0064]

number

[0065] <Drilling work, tip-off> The wheel loader 1 of this embodiment performs excavation work by excavating an excavation target such as earth and sand with the bucket 14 and scooping the excavation target into the bucket 14. After the excavation work, the wheel loader 1 calculates a load mass W load 3 is a schematic diagram illustrating tipping off after an excavation operation by the wheel loader 1 according to the embodiment.

[0066] As shown in Fig. 3(A), the wheel loader 1 moves forward toward the excavation target 100 and causes the cutting edge 14a of the bucket 14 to bite into the excavation target 100, and then raises the bucket 14 along the bucket trajectory L and moves the bucket 14 in the tilt direction, as shown by the arrow in Fig. 3(A). In this way, an excavation operation is performed in which the excavation target 100 is scooped into the bucket 14.

[0067] As shown in Figure 3(B), after the excavation target 100 has been scooped into the bucket 14, the wheel loader 1 moves backward in the load reverse process. As shown in Figure 3(C), the wheel loader 1 raises the boom 15 at a slow speed. As shown in Figure 3(D), the wheel loader 1 moves the bucket 14 in the dump direction while raising the boom 15. The wheel loader 1 drops a portion of the excavation target 100 in the bucket 14 from the bucket 14, reducing the load mass W loadand the load mass W in the bucket 14 is reduced. load The tip-off is performed by bringing the load mass closer to the target value, which is the target load mass.

[0068] Load mass W in bucket 14 load When tip-off is performed until the load mass W is close enough to the target load mass, load It is determined that the bucket 14 has finished decreasing, and as shown in FIG. 3(E), the bucket 14 moves in the tilt direction. The bucket 14 moves to a full tilt state. A full tilt state means that the front end of the bucket 14 is raised until the bucket 14 stops at the tilt-side stopper. When the bucket 14 is in a full tilt state, the bucket cylinder 19 is at the stroke end on the extension side. When the bucket 14 is in a full tilt state, the bucket ground angle θ B takes the maximum positive value.

[0069] Thereafter, the wheel loader 1 performs a loading operation in which the excavation target 100 in the bucket 14 is loaded onto a transport machine such as a dump truck.

[0070] <Functional configuration> Next, a description will be given of the functional configuration of the wheel loader 1. In particular, a description will be given of the functional blocks of the controller 50 that automatically executes tipping off (auto-tip off) after excavation work in the wheel loader 1 shown in Fig. 1, using Fig. 4.

[0071] FIG. 4 is a functional block diagram showing the functional configuration of the wheel loader 1. As shown in FIG. 4, the wheel loader 1 includes a controller 50, an input unit 51, and a display unit 52. The input unit 51 includes an input device such as an operation panel. The operation panel may be configured to include hard keys and / or software keys. The input unit 51 includes an operation lever for the work implement 3. The display unit 52 corresponds to a monitor. The input unit 51 and the display unit 52 are installed inside the cab 5. The display unit 52 may be a touch panel. The display unit 52 may have some of the functions of the input unit 51.

[0072] The controller 50 includes a memory unit 500, a boom cylinder thrust calculation unit 501, a hydraulic transmission efficiency calculation unit 502, a dimension value calculation unit 503, a bucket ground angle calculation unit 505, a target load mass calculation unit 508, a load mass calculation unit 509, an automatic tip-off control unit 510, and a table calibration unit 530. The automatic tip-off control unit 510 includes an auto-tip-off start determination unit 511, an auto-tip-off control unit 512, and an auto-tip-off end determination unit 513.

[0073] The storage unit 500 stores in advance various data input via the input unit 51. The storage unit 500 stores the mass Wg of the bucket 14. bucket and the mass W of the entire work machine 3 we , the empty load correction coefficient β, the work implement design dimension values, the work implement design center of gravity position, and the capacity of the bucket 14 are stored.

[0074] The work machine design dimension values ​​are the design dimension values ​​of each component that constitutes the work machine 3, such as the bucket 14, boom 15, bell crank 16, tilt rod 17, etc. For the boom 15, the work machine design dimension values ​​are, for example, the distance between the through hole into which the boom foot pin 21 is inserted and the through hole into which the bucket pin 22 is inserted, the distance between the through hole into which the boom foot pin 21 is inserted and the through hole into which the pin 24 is inserted, etc.

[0075] The work implement design center of gravity position is the theoretical value of the position of the center of gravity GC1 of the work implement 3. The work implement design center of gravity position is the center of gravity position in a coordinate system specific to the work implement 3. The work implement design center of gravity position is expressed as a coordinate value with respect to the work implement 3 when a specific position of the work implement 3 is set as the origin. The position of the origin can be set so that the work implement design center of gravity position can be expressed in a two-dimensional coordinate system. For example, the center of the through hole into which the boom foot pin 21 is inserted in a side view of the boom 15 can be set as the specific position (origin).

[0076] The work implement design dimension values ​​are used in the dimension value calculation unit 503. The work implement design center of gravity position and the mass Wg of the bucket 14 bucket and the mass W of the entire work machine 3 weand the empty load correction coefficient β are used in the cargo mass calculation unit 509.

[0077] The storage unit 500 also stores a table showing the relationship between the mass of the load in the bucket 14 and the attitude of the bucket 14. The attitude of the bucket 14 is determined by the angle of the bucket 14 with respect to the ground G, i.e., the bucket ground angle θ B It is defined by:

[0078] The boom cylinder thrust calculation unit 501 calculates the thrust F of the boom cylinder 18 described above based on the cylinder pressure detected by the pressure sensors 31b and 31h. cyl Specifically, the boom cylinder thrust calculation unit 501 calculates the thrust F based on the bottom pressure of the boom cylinder 18 obtained from the pressure sensor 31b and the head pressure obtained from the pressure sensor 31h. cyl The boom cylinder thrust calculation unit 501 periodically calculates the thrust F from only the bottom pressure of the boom cylinder 18 that has been acquired. cyl The calculated thrust F cyl The value is sent to the cargo mass calculation unit 509.

[0079] The hydraulic transmission efficiency calculation unit 502 calculates the hydraulic transmission efficiency η of the boom 15 based on the value of the boom angle detected by the sensor that detects information related to the boom angle described above. Specifically, the hydraulic transmission efficiency calculation unit 502 calculates the amount of change per unit time in the value of the boom angle, and determines the hydraulic transmission efficiency η based on this amount of change. The hydraulic transmission efficiency calculation unit 502 sends the calculated hydraulic transmission efficiency η to the load mass calculation unit 509. The calculated hydraulic transmission efficiency η is substituted into the above-mentioned equation (3).

[0080] As described above, instead of calculating the hydraulic transmission efficiency η each time, a predetermined constant value may be used as the hydraulic transmission efficiency η.

[0081] The dimension value calculation unit 503 calculates the values ​​of the above-mentioned dimensions Rli (i = 1 to 3) and Rbj (j = 1 to 6) using the above-mentioned work machine design dimension values, boom angle, and bell crank angle θ2 stored in the memory unit 500. The dimension value calculation unit 503 periodically calculates the values ​​of the dimensions Rli (i = 1 to 3) and Rbj (j = 1 to 6). The dimension value calculation unit 503 sends the calculation results to the load mass calculation unit 509.

[0082] The bucket ground angle calculation unit 505 calculates the bucket ground angle θ using the above-mentioned work machine design dimension values, boom angle, and bell crank angle θ2 stored in the storage unit 500. B The bucket ground angle calculation unit 505 sends the calculation result to the auto tip-off control unit 512 and the table calibration unit 530.

[0083] The target load mass calculation unit 508 calculates the target soil volume (target load mass), which is the target value for the mass of the load loaded in the bucket 14 at the end of tipping off, based on the maximum load capacity of the transport machine input via the input unit 51 and the capacity of the bucket 14. The target load mass calculation unit 508 sends the calculation result to the auto tip-off start determination unit 511, the auto tip-off control unit 512, and the auto tip-off end determination unit 513.

[0084] The cargo mass calculation unit 509 calculates each mass Wg bucket ,W we , correction coefficient β, and thrust F cyl The cargo mass calculation unit 509 periodically calculates the cargo mass using the above-mentioned equations (1) to (6) based on the hydraulic transmission efficiency η and the dimensions Rli (i = 1 to 3) and Rbj (j = 1 to 6). The cargo mass calculation unit 509 periodically sends the calculated cargo mass value to the auto tip-off start determination unit 511, the auto tip-off control unit 512, the auto tip-off end determination unit 513, and the table calibration unit 530.

[0085] The table calibration unit 530 calibrates the bucket ground angle θ calculated by the bucket ground angle calculation unit 505. Band the cargo mass calculated by cargo mass calculation unit 509, the table stored in memory unit 500 that indicates the relationship between the cargo mass in bucket 14 and the attitude of bucket 14 is corrected. Table calibration unit 530 sends the corrected table to auto tip-off control unit 512 and display unit 52.

[0086] The auto-tip-off start determination unit 511, auto-tip-off control unit 512, and auto-tip-off end determination unit 513 perform auto-tip-off control based on operation information of the operating lever for the work implement 3 input via the input unit 51, the calculated target soil volume, and the load mass. The auto-tip-off control unit 512 outputs control signals indicating flow rate commands to the boom cylinder 18 and bucket cylinder 19. The automatic tip-off control unit 510 causes the display unit 52 to display information.

[0087] <Control Structure> FIG. 5 is a flow chart for explaining the flow of the auto tip-off control process executed by the controller 50. As shown in FIG.

[0088] In step S1, the excavation work ends. The excavation work may be performed automatically, or the operator may perform the excavation work manually. The controller 50 recognizes that excavation has ended. The controller 50 determines that the excavation operation of the wheel loader 1 has ended based on the operation details of the operating lever for traveling (forward and backward movement) and the operating lever for the work implement 3, information about the attitude of the work implement 3, information about the thrust of the boom cylinder 18, information about the thrust of the bucket cylinder 19, etc.

[0089] In step S2, the wheel loader 1 moves backward with the load. The operator may move the wheel loader 1 backward manually. The controller 50 may also move the wheel loader 1 backward automatically with the load. The controller 50 may send a control signal to the traveling device 4 to move the wheel loader 1 backward while maintaining the attitude of the work implement 3 and keeping the load loaded in the bucket 14.

[0090] In step S3, the operator operates the tip-off start button. The controller 50 (auto-tip-off start determination unit 511 of the automatic tip-off control unit 510) receives input that the tip-off start button has been pressed. The tip-off start button is a button that is operated by the operator to start auto-tip-off. The input unit 51 includes the tip-off start button. By including the pressing of the tip-off start button in the conditions for starting auto-tip-off, it becomes possible to perform tip-off automatically in accordance with the will of the operator who wishes to perform auto-tip-off.

[0091] A physical push button switch may be arranged in the cab 5 as the tip-off start button, and the push button switch may be electrically connected to the controller 50 so that an operator can input an operation of pressing the push button switch into the controller 50. Alternatively, the controller 50 may display the tip-off start button on the display unit 52, which is a touch panel.

[0092] In step S4, the controller 50 (auto tip-off start determination unit 511) recognizes that the dump operation of the bucket 14 has continued for one second. A dump operation means that the control lever for the work implement 3 is operated in a direction that moves the bucket 14 in the dump direction. The controller 50 receives input of the operation content of the control lever from the control lever for the work implement 3. The controller 50 determines that the control lever for the work implement 3 has been operated to dump, and that the dump operation has continued for one second.

[0093] When the tip-off start button is pressed in step S3 and the dump operation of the bucket 14 continues for one second in step S4, the controller 50 (auto-tip-off control unit 512 of the automatic tip-off control unit 510) raises the boom 15 in step S5. The controller 50 outputs a control signal to extend the boom cylinder 18. Hydraulic oil flows into the oil chamber on the bottom side of the boom cylinder 18, and the piston 18c moves toward the tip of the tube 18a, thereby extending the boom cylinder 18. As the boom cylinder 18 extends, the boom 15 rises.

[0094] In step S6, the controller 50 (auto tip-off control unit 512) determines whether the post-excavation soil volume, which is the load mass in the bucket 14 after the excavation work, is greater than the target soil volume (target load mass), which is the target value for the load mass in the bucket 14.

[0095] 6 is a flow chart showing the flow of a process for calculating the target soil volume. The controller 50 automatically calculates the target value of the load mass in excavation work from the maximum load capacity of the dump truck and the capacity of the bucket 14.

[0096] In step S101, a loading operation is started in which the cargo in the bucket 14 is loaded onto a dump truck, which is an example of a conveying machine. The wheel loader 1 is caused to travel forward toward the dump truck, and the bucket 14 is moved onto the bed of the dump truck, and the bucket 14 is then moved in the dumping direction, whereby the cargo in the bucket 14 is loaded onto the bed of the dump truck. The loading operation may be performed manually by an operator, or may be performed automatically by the controller 50.

[0097] In step S102, the controller 50 acquires the maximum load capacity of the bed of the dump truck that is the target of the loading operation. The operator inputs the maximum load capacity of the dump truck by operating the input unit 51. In response to the operator's input, the controller 50 acquires the maximum load capacity of the dump truck.

[0098] In step S103, the controller 50 determines whether the auto tip-off mode is ON. Based on the operator's operation, it is set whether auto tip-off is performed after excavation work (auto tip-off mode ON) or whether tip-off is performed manually after excavation work and auto tip-off is not performed (auto tip-off mode OFF). The operator may set the auto tip-off mode by operating the input unit 51. The setting of the auto tip-off mode may be displayed on the display unit 52.

[0099] If it is determined that the auto tip-off mode is ON (YES in step S103), in step S104, the controller 50 determines whether the remaining amount of cargo that can be loaded onto the bed of the dump truck is smaller than the capacity of the bucket 14. The controller 50 acquires the amount of cargo loaded onto the dump truck at the time the loading operation in step S101 is completed and the maximum load capacity of the dump truck.

[0100] The controller 50 calculates the remaining load capacity by subtracting the amount of cargo already loaded on the dump truck from the maximum load capacity of the dump truck. The controller 50 compares the capacity of the bucket 14 stored in the memory unit 500 with the calculated remaining load capacity to determine whether the remaining load capacity is smaller than the capacity of the bucket 14.

[0101] If it is determined that the remaining load capacity is smaller than the capacity of the bucket 14 (YES in step S104), in step S105, the controller 50 sets the weight obtained by adding the margin value N to the remaining load capacity calculated in step S104 as the target soil volume (target load mass), which is the target value for the load mass in the bucket 14 during auto tip-off. The controller 50 sets a larger load mass for tip-off. By loading a larger load into the bucket 14 during excavation work and then discharging the excess load from the bucket 14 during tip-off, the accuracy of the load mass in the bucket 14 at the end of tip-off can be improved.

[0102] If it is determined in step S103 that the auto tip-off mode is OFF (NO in step S103), or if it is determined in step S104 that the capacity of the bucket 14 is equal to or greater than the remaining load capacity (NO in step S104), then in step S106, controller 50 performs a calculation to divide the maximum load capacity of the dump truck by the capacity of the bucket 14. From the result of this calculation, controller 50 calculates an equally distributed excavation amount by equally dividing the maximum load capacity of the dump truck.

[0103] In step S107, the operator operates the automatic excavation enable button on the input unit 51 to input a command to start automatic excavation. The automatic excavation enable button may be a physical push button switch, or may be displayed on the display unit 52, which is a touch panel. In response to this input, the controller 50 starts automatic excavation of the excavation target by the wheel loader 1. In this way, a series of processes for calculating the target soil volume is performed.

[0104] 5, if the determination in step S6 is that the target soil volume is smaller than the post-excavation soil volume, that is, the load mass, which is the mass of the excavation target in bucket 14 after excavation work, is greater than the target value for the load mass in bucket 14 (target load mass) (YES in step S6), then in step S7, controller 50 (auto-tip-off control unit 512) starts auto-tip-off. The operation of raising boom 15, which was started in step S5, continues during auto-tip-off.

[0105] In step S8, the controller 50 drives the bucket cylinder 19 to move the bucket 14 in the dumping direction. FIG. 7 is a schematic diagram showing the processing content of the dumping control. As shown in FIG. 7, in the dumping control to move the bucket 14 in the dumping direction, the load mass and the attitude of the bucket 14 (specifically, the bucket ground angle θ B ) and the target bucket ground angle θ T7 shows an example of the relationship between the load mass and the attitude of the bucket 14. The table T1 is stored in the storage unit 500.

[0106] For example, the table T1 is configured to maximize the mass of the load in the bucket 14, discharge the load from the bucket 14, and calculate the mass of the load in the bucket 14 and the attitude of the bucket 14 (bucket ground angle θ B It can be created by obtaining the following:

[0107] In table T1, the horizontal axis represents the soil volume (unit: ton), and the vertical axis represents the bucket ground angle θ B (Unit: deg) As mentioned above, the bucket ground angle θ B When the bucket angle θ is 0°, the back surface 14b of the bucket 14 is parallel to the ground G. B When the angle θ is a positive value, the back surface 14b of the bucket 14 is inclined with respect to the ground G so that the back surface 14b is positioned higher as it approaches the cutting edge 14a. B When is a negative value, the back surface 14b of the bucket 14 is inclined with respect to the ground G so that it is positioned lower as it approaches the cutting edge 14a. B The curve is a smoothed result of determining the amount of soil in the bucket 14 for each value.

[0108] In auto tip-off, the controller 50 performs a dump operation on the bucket 14. The load in the bucket 14 is dropped from the cutting edge 14a side, reducing the load mass in the bucket 14 and bringing the load mass closer to the calculated target soil volume. The controller 50 calculates the target bucket ground angle θ based on the calculated target soil volume and the curve shown in table T1. T The controller 50 determines the bucket angle relative to the ground θ when the target volume of soil is contained in the bucket 14. B The target bucket ground angle θ T It is defined as follows.

[0109] The controller 50 controls the bucket ground angle θB The target bucket angle θ T The controller 50 operates the bucket 14 in the dump direction to a position where the bucket 14 assumes a dumping position, thereby discharging the excavated object from the bucket 14. As a result, the controller 50 reduces the load mass in the bucket 14. The controller 50 operates the bucket 14 in the dump direction to a position where the bucket ground angle θ B The bucket's ground angle θ is aimed at T Get closer to.

[0110] In dump control, the controller 50 moves the bucket 14 in the dump direction at a constant speed. The controller 50 determines the speed of the bucket 14 toward the target attitude based on the target soil volume (target load mass). In table T2 shown in FIG. 7, the horizontal axis represents the target soil volume (unit: ton) and the vertical axis represents the target bucket flow rate (unit: %). The target bucket flow rate is the flow rate of hydraulic oil supplied to the bucket cylinder 19. Table T2 is stored in the memory unit 500.

[0111] To move the bucket 14 in the tilt direction, the length of the bucket cylinder 19 is increased. Hydraulic oil flows into the oil chamber on the bottom side of the bucket cylinder 19. At this time, the target bucket flow rate is assumed to be a positive value. To move the bucket 14 in the dump direction, the length of the bucket cylinder 19 is decreased. Hydraulic oil flows into the oil chamber on the head side of the bucket cylinder 19. At this time, the target bucket flow rate is assumed to be a negative value.

[0112] Table T2 shows an example of a target bucket flow rate in dump control. When performing auto-tip-off, the bucket 14 moves in the dump direction. Therefore, the vertical axis of table T2 takes on a range of negative values. When the target bucket flow rate is 0%, the amount of hydraulic oil flowing into the head-side oil chamber of the bucket cylinder 19 is zero. When the target bucket flow rate is minus 100%, the amount of hydraulic oil flowing into the head-side oil chamber of the bucket cylinder 19 is at its maximum. The closer the target bucket flow rate is to 0%, the slower the speed of the bucket 14. The closer the target bucket flow rate is to minus 100%, the faster the speed of the bucket 14 moving in the dump direction.

[0113] As shown in table T2, the controller 50 increases the speed of the bucket 14 moving in the dump direction as the target soil volume decreases. When the target soil volume is small, it is necessary to discharge a large amount of the load loaded in the bucket 14, and the target bucket ground angle θ T becomes a small value. Therefore, the speed of the bucket 14 is increased to discharge the load from the bucket 14 in a shorter time, so that the load mass can be reduced in a short time. On the other hand, if the target soil volume is large, the amount of load discharged from the bucket 14 does not need to be small, so the speed of the bucket 14 is reduced to prevent excessive discharge of the load.

[0114] The target bucket flow rate determined by the target soil volume (target load mass) is converted into a flow rate / voltage to determine the bucket lever voltage. This flow rate / voltage conversion may be performed by the controller 50 or by a vehicle controller mounted on the wheel loader 1. The bucket cylinder 19 is controlled using this determined bucket lever voltage as a control variable in dump control. In this way, the operation of moving the bucket 14 in the dump direction to reduce the load mass in the bucket 14 is performed automatically.

[0115] Returning to FIG. 5, in step S9, the controller 50 (auto tip-off control unit 512) calculates the current bucket ground angle θ B and the target bucket ground angle θ TThe current bucket ground angle θ B The target bucket angle θ T If so (NO in the determination in step S9), the process returns to step S8, and the controller 50 continues the dump control.

[0116] Current bucket ground angle θ B The target bucket angle θ T (YES in step S9), the controller 50 determines that the load mass in the bucket 14 has been reduced. The controller 50 ends dump control for moving the bucket 14 in the dump direction. In step S10, the controller 50 performs tilt control for moving the bucket 14 in the tilt direction. The controller 50 adjusts the bucket ground angle θ B Based on this, the control switches from dump control to tilt control.

[0117] When the current bell crank angle θ2 reaches the target angle by moving the bucket 14 in the tilt direction, the controller 50 ends the auto tip-off in step S11.

[0118] In the determination in step S6, if the target soil volume is equal to or greater than the post-excavation soil volume, that is, if the load mass, which is the mass of the excavation target in the bucket 14 after excavation work, is equal to or less than the target value for the load mass in the bucket 14 (target load mass) (NO in the determination in step S6), it is not necessary to perform tip-off and adjust the load mass in the bucket 14. In this case, the process proceeds to step S11, and the controller 50 ends auto tip-off.

[0119] Upon completion of auto tip-off, automatic control of the work implement 3 may be released. When automatic control is released, the work implement 3 will operate in accordance with manual operation of the operating lever for the work implement 3 by the operator. Alternatively, after completion of auto tip-off, the controller 50 may automatically perform loading work.

[0120] <Calibration of the relationship between load mass and bucket attitude> Below, a description will be given of calibration for correcting table T1 ( FIG. 7 ), which indicates the relationship between the mass of the load in the bucket 14 and the attitude of the bucket 14. As described with reference to FIG. 7 , the controller 50 uses table T1 to discharge the load in the bucket 14 from the bucket 14. In the embodiment, table T1 is pre-stored in the storage unit 500 ( FIG. 4 ), but this is not limited to this example. Table T1 may also be pre-stored in an external storage device that can communicate with the controller 50. The controller 50 may read table T1 from the storage unit 500 or from an external storage device.

[0121] The calibration of the table T1 in the embodiment includes normal calibration and simple calibration. In the normal calibration, the mass of the load in the bucket 14 is maximized, and then the load is discharged from the bucket 14, and the mass of the load in the bucket 14 and the attitude of the bucket 14 (bucket ground angle θ B ) to correct table T1. Simple calibration is a process of obtaining the mass of the load in the bucket 14 in one specific bucket posture and correcting table T1 based on the obtained mass of the load. The controller 50 (table calibration unit 530) selectively executes either normal calibration or simple calibration.

[0122] <Normal calibration> Fig. 8 is a flow diagram for explaining the processing flow of normal calibration. Fig. 9 is a schematic diagram of a screen displayed on display unit 52 during normal calibration. During normal calibration, normal calibration screen 520 is displayed on display unit 52. Normal calibration screen 520 includes a calibration start button 521, a material selection section 522, a boom angle input section 523, a bucket ground angle input section 524, a reset button 525, and a correction table 529. Normal calibration screen 520 also includes displays showing the normal calibration procedure, specifically, displays (1) to (4) on the left side of the screen.

[0123] Before starting normal calibration, the operator operates the input unit 51 to input, into the boom angle input unit 523, the boom angle at which the load in the bucket 14 can be discharged from the bucket 14. The operator operates the input unit 51 to input, into the boom angle input unit 523, the bucket ground angle θ at which the load in the bucket 14 can be completely discharged and the load mass in the bucket 14 can be made zero. B is input into bucket ground angle input section 524. In the example shown in Fig. 9, 0.0° is input into boom angle input section 523, and -50.0° is input into bucket ground angle input section 524. By pressing reset button 525, the operator can delete the input contents into boom angle input section 523 and bucket ground angle input section 524.

[0124] In step S201 shown in Fig. 8, excavation work is performed to fill the bucket 14 with a load, as shown in procedure (1) in Fig. 9. The load mass in the bucket 14 is maximized. This excavation work may be performed manually by an operator, or may be performed automatically by the controller 50.

[0125] In step S202, as shown in procedure (2) in Fig. 9, the boom 15 is raised to make the boom angle equal to or greater than the angle input to the boom angle input unit 523. The operator may raise the boom 15 manually, or the controller 50 may raise the boom 15 automatically. After the boom angle is made equal to or greater than the angle input to the boom angle input unit 523, the boom 15 stops. Thereafter, the boom 15 remains stopped.

[0126] In step S203, a material is selected. The operator clicks the downward-pointing triangle mark shown at the right end of the material selection section 522 to select the material to be normally calibrated. In the example shown in Fig. 9, material A is selected. By selecting the material to be calibrated, it becomes possible to manage tables for each material.

[0127] In step S204, as shown in step (3) in FIG. 9, the calibration start button 521 is pressed. The calibration start button 521 can be pressed by clicking the mouse with the mouse pointer positioned on the calibration start button 521 or by tapping the calibration start button 521. The calibration start button 521 shown in FIG. 9 displays "Calibrating." The normal calibration screen 520 shown in FIG. 9 displays the calibration start button 521 after it has been pressed. Before it is pressed, the calibration start button 521 displays, for example, "Start calibration."

[0128] When calibration start button 521 is pressed, bucket 14 is moved at a low speed in the dump direction as shown in step (4) in FIG. 9. By moving bucket 14 in the dump direction, the load is discharged from bucket 14. The load in bucket 14 falls from cutting edge 14a, and the load mass decreases. This movement of bucket 14 may be performed manually by an operator, or may be performed automatically by controller 50.

[0129] In step S205, the instantaneous load is acquired. The instantaneous load is the current load mass in the bucket 14. Also, the bucket ground angle θ B is acquired. While the bucket 14 is being moved in the dump direction to discharge the load, the controller 50 acquires the load mass and the attitude of the bucket 14. The controller 50 (load mass calculation unit 509) calculates the instantaneous load using the above-mentioned equations (1) to (6). The controller 50 (bucket ground angle calculation unit 505) calculates the bucket ground angle θ using the work implement design dimension values, the boom angle, and the bell crank angle θ2. B Calculate.

[0130] In step S206, the bucket ground angle θ B In the embodiment, the determination is made by calculation using a mod function. The mod function is a function that calculates the remainder when a numerical value is divided by a divisor. "mod (bucket ground angle, 10)" shown in FIG. 8 is the bucket ground angle θ B is obtained by dividing by 10. In step S206, the controller 50 calculates the bucket ground angle θ B The controller 50 determines whether the remainder when the bucket ground angle θ B Determine whether is a multiple of 10.

[0131] Bucket ground angle θ B If the remainder when divided by 10 is not 0 (NO in step S206), the process returns to step S205. B and the bucket ground angle θ in step S206 B and the determination regarding the number of times ...

[0132] Bucket ground angle θ BIf the remainder when divided by 10 is 0 (YES in step S206), in step S207, the controller 50 calculates the instantaneous load and the bucket ground angle θ B The controller 50 stores the instantaneous load and the bucket ground angle θ B The controller 50 stores the bucket ground angle θ obtained in step S205 in the correction table 529 shown in FIG. B and the instantaneous load (corresponding to "soil volume" on the vertical axis of the correction table 529) are plotted.

[0133] In step S208, the bucket ground angle θ plotted in the correction table 529 in step S207 is B is equal to or less than the designated angle. This designated angle is the angle input to the bucket ground angle input section 524. Bucket ground angle θ B is greater than the designated angle (NO in step S208), the process returns to step S205. B In step S206, the bucket ground angle θ B , the plot in step S207, and the bucket ground angle θ in step S208. B This judgment is repeated.

[0134] Bucket ground angle θ B becomes equal to or smaller than the designated angle (YES in step S208), the table is corrected in step S209. B The bucket 14 is moved in the dump direction from a position where the bucket ground angle θ is +50°, and the bucket ground angle θ is plotted every 10°. B The dumping operation of the bucket 14 continues until the attitude of the bucket 14 reaches -50°, and adjacent plots are connected by straight lines to form a correction table 529. The controller 50 stores the correction table 529 in the memory unit 500.

[0135] In this way, the correction of table T1 by normal calibration is completed. The controller 50 uses the corrected table T1 (correction table 529) to unload the load from the bucket 14.

[0136] <Simple calibration> Fig. 10 is a flow diagram for explaining the processing flow of the simple calibration. When the simple calibration is performed, as shown in Fig. 10, in step S301, an excavation operation is performed and the load in the bucket 14 is filled up. The load mass in the bucket 14 is maximized. This excavation operation may be performed manually by an operator or automatically by the controller 50.

[0137] In step S302, the controller 50 (load mass calculation unit 509) calculates the load mass in the bucket 14 when it is fully loaded using the above-described equations (1) to (6). The controller 50 (load mass calculation unit 509) calculates the maximum load mass. The controller 50 obtains the maximum amount of load that can be loaded into the bucket 14. The controller 50 obtains the mass of the load in the bucket 14 in the attitude that maximizes the load mass. If the load mass is calculated while the boom 15 is raised at a low speed, it is possible to calculate the load mass more accurately.

[0138] In step S303, the controller 50 receives an input to select the excavation target (material) to be excavated by the bucket 14. The operator operates the input unit 51 to input to the controller 50 the type of material that has been excavated in the processing of step S301 and is loaded into the bucket 14.

[0139] In step S304, the controller 50 determines whether the material selected in step S303 is a load mass and a bucket ground angle θ B The relationship between the load mass and the bucket ground angle θ is not memorized for the new material. BIt is determined whether the relationship between the two is already stored and whether the material is new.

[0140] If it is determined that the material is new (YES in step S304), the controller 50 refers to a default table in step S305. FIG. 11 is a diagram showing an example of a stored default table. The default table contains a relationship between the load mass (corresponding to the "soil volume" on the horizontal axis in FIG. 11) and the bucket ground angle θ B The default table is stored in advance in the storage unit 500 when the wheel loader 1 is shipped from the factory.

[0141] In step S306, the controller 50 sets the load mass acquired in step S302 as the capacity of the bucket 14, which indicates the maximum amount of load that can be loaded into the bucket 14. The controller 50 stores the capacity of the bucket 14 currently attached to the tip of the work implement 3 in the memory unit 500.

[0142] In step S307, the controller 50 obtains the originally set bucket capacity. The originally set bucket capacity here is the maximum value of the load mass (soil volume) determined by the default table shown in Fig. 11 or another table stored in the storage unit 500. The originally set bucket capacity is the load mass determined by the pre-stored table when the bucket 14 is in the posture that maximizes the load mass.

[0143] The controller 50 calculates the ratio between the originally set bucket capacity and the current bucket capacity saved in step S306. Specifically, the controller 50 calculates a quotient by dividing the current bucket capacity as the dividend and the originally set bucket capacity as the divisor. This quotient does not need to be a natural number, as long as it is calculated as a rational number.

[0144] The controller 50 refers to the default table and calculates a certain bucket ground angle θ BThe controller 50 calculates the load mass in tons for each of the calculated bucket ground angles θ B The controller 50 multiplies the value of the cargo mass at this time by the quotient calculated above. The controller 50 calculates the cargo mass obtained by this calculation and the bucket ground angle θ at this time. B The controller 50 obtains a modified table by connecting or smoothing the multiple plots. In this way, the controller 50 modifies the default table. In step S308, the controller 50 stores the modified table in the storage unit 500.

[0145] Fig. 12 is a diagram showing an example of table modification for a first material. The dashed lines shown in Fig. 12 are the tables shown in solid lines in the default table of Fig. 11. The solid lines shown in Fig. 12 are tables obtained by modifying the default table.

[0146] FIG. 12 shows an example of table correction when the current bucket capacity is larger than the originally set bucket capacity. The quotient of the current bucket capacity divided by the originally set bucket capacity is larger than 1. By correcting the soil volume value in the default table by multiplying it by a value larger than 1, the corrected table shown by the solid line in FIG. 11 is an expanded version of the default table in the horizontal direction. By making an adjustment to expand the default table, the controller 50 can adjust the load mass and the bucket ground angle θ B Change your relationship with

[0147] If it is determined in step S304 that the material is not new (NO in step S304), in step S309, the controller 50 refers to the stored table for each material. Then, in step S306, the controller 50 saves the current bucket capacity. In step S307, the controller modifies the table referred to in step S309.

[0148] Fig. 13 is a diagram showing an example of modifying a table for a second material. The dashed lines shown in Fig. 13 are tables created and stored by previously modifying the default table for the second material. A table is stored for each material. The solid lines shown in Fig. 13 are tables obtained by modifying the dashed table.

[0149] FIG. 13 shows an example of table correction when the current bucket capacity is smaller than the originally set bucket capacity determined by the pre-stored table shown by the dashed line. The quotient obtained by dividing the current bucket capacity by the originally set bucket capacity is smaller than 1. By correcting the soil volume value in the default table by a value smaller than 1, the corrected table shown by the solid line in FIG. 13 is a table that has been reduced in size in the horizontal axis direction from the pre-stored table. By performing an adjustment to reduce the pre-stored table, the controller 50 can reduce the load mass and the bucket ground angle θ B Change your relationship with

[0150] In this way, the table correction by the simple calibration is completed. The controller 50 uses the corrected table to discharge the load from the bucket 14.

[0151] 10 to 13, an example of correcting the table when the excavation target (material) is changed has been described. However, the present invention is not limited to this example, and the table can also be corrected by simple calibration when the bucket 14 is changed.

[0152] Fig. 14 is a diagram showing an example of table modification when a bucket 14 is changed. The dashed lines shown in Fig. 14 are tables that are pre-stored for a specific bucket. The solid lines shown in Fig. 14 are tables obtained by modifying the dashed line table.

[0153] FIG. 14 shows an example of table correction when the capacity of the bucket 14 currently attached to the work implement 3 is larger than the bucket capacity determined by the pre-stored table shown by the dashed line. The corrected table shown by the solid line in FIG. 14 is an enlargement of the pre-stored table in the horizontal axis direction. The controller 50 adjusts the pre-stored table to enlarge it, thereby adjusting the load mass and the bucket ground angle θ B Change your relationship with

[0154] In the above description of the simple calibration, the load mass in the bucket 14 is maximized in step S301, and the table is corrected based on the load mass in the bucket 14 in the orientation where the bucket 14 is full of load. The orientation of the bucket 14 when acquiring the load mass for the simple calibration does not have to be the orientation where the bucket 14 is full of load. Bucket ground angle θ B If the load mass when the load angle is at a specific angle can be obtained, the table can be corrected based on the obtained load mass. The specific angle may be set by an operator or by the controller 50.

[0155] <Calibration taking into account the angle of repose of the material being excavated> The angle of repose of the material to be excavated varies depending on the type and condition of the material. If the angle of repose of the material to be excavated is known in advance, the table can be modified by adding an offset in the vertical axis direction that takes that angle of repose into account.

[0156] For example, the operator can input the angle of repose of the material to be excavated by operating the input unit 51. The controller 50 can acquire the angle of repose of the material based on the operator's input. Furthermore, for example, the controller 50 can estimate the angle of repose of the material from an image of the natural ground of the material or an image of the material in the bucket 14 captured by the imaging device 39 (FIG. 1). The controller 50 can acquire the estimated angle of repose of the material.

[0157] Figure 15 shows an example of table modification when the angle of repose of a material is changed. The dashed line in Figure 15 is a pre-stored table for when a material with a specific angle of repose is excavated with a specific bucket. The solid line in Figure 15 is a table obtained by modifying the dashed line table, and is a table for when a material with a different angle of repose, specifically a material with a smaller angle of repose, is excavated with the same bucket.

[0158] When the bucket 14 is moved in the dump direction to discharge material from the cutting edge 14a, material with a small angle of repose is more likely to fall from the bucket 14 than material with a large angle of repose. The corrected table shown by the solid line in Figure 15 is a table that has been stored in advance and offset in the vertical direction (specifically, upward). The controller 50 adjusts the pre-stored table by offsetting it vertically based on the acquired angle of repose information, thereby obtaining a corrected value for the load mass and the bucket ground angle θ B For material with a small angle of repose, the attitude of the bucket 14 when the load in the bucket 14 is completely discharged is such that the inclination of the back surface 14b with respect to the ground G is smaller.

[0159] The controller 50 also performs the simple calibration described above to correct the table by scaling the table laterally based on the orientation of one particular bucket 14 .

[0160] Calibration that takes into account the angle of repose of the material can be performed by performing two processes: a process to offset the table in the vertical axis direction depending on the difference in the angle of repose of the material, and a process to scale the table in the horizontal axis direction depending on the difference in the density of the material or the bucket 14.

[0161] <Action and effect> The characteristic configuration and effects of this embodiment are summarized as follows.

[0162] 11, a table is stored in advance that indicates the relationship between the load mass, which is the mass of the load in the bucket 14, and the attitude of the bucket 14. As shown in FIG. 12, the controller 50 (table calibration unit 530) obtains the load mass in one specific bucket attitude, and corrects the pre-stored table based on the obtained load mass.

[0163] If the type, specific gravity, or angle of repose of the load is different, or if the specifications of the bucket 14 are different, the mass of the load contained in the bucket 14 may change even when the bucket 14 is in the same attitude. By acquiring the mass of the load actually contained in the bucket 14 and correcting the relationship between the load mass and the attitude of the bucket 14 based on the acquired load mass, it is possible to accurately determine the mass of the load in the bucket 14 when the bucket 14 is in a certain attitude. Therefore, the accuracy of the relationship between the load mass in the bucket 14 and the attitude of the bucket 14 can be improved.

[0164] 10 and 12, the controller 50 may acquire the load mass when the attitude of the bucket 14 is the above-mentioned specific bucket attitude, and may correct the table using the ratio between the acquired load mass and the load mass determined by the stored table. The value of the corrected load mass is calculated by multiplying the load mass determined by the pre-stored table when the bucket 14 is in a certain attitude by the ratio. The corrected values ​​of the load mass when the bucket 14 is in each attitude are calculated and plotted, thereby obtaining the corrected table.

[0165] As shown in Figures 5 and 7, the controller 50 may use a modified table to discharge a load from the bucket 14. By using a table with improved accuracy in the relationship between load mass and bucket 14 attitude, the load mass in the bucket 14 can be accurately reduced toward a target value when discharging a load from the bucket 14. The timing for completing load discharge can be determined appropriately, improving the accuracy of the load mass in the bucket 14 when the load has been discharged. The amount of load to be loaded from the wheel loader 1 onto the conveying machine can be accurately adjusted.

[0166] 10 and 12, the particular bucket attitude may be the attitude of the bucket 14 at which the load mass is at its maximum. The relationship between the load mass and the attitude of the bucket 14 can be easily corrected by the simple operation of filling the bucket 14 with the load.

[0167] 11 and 12, the specific bucket attitude may be defined by the angle of the bucket 14 with respect to the ground surface G. A sensor mounted on the wheel loader 1 can detect information relating to the angle of the bucket 14 with respect to the ground surface G, so it is possible to easily bring the bucket 14 into a specific attitude based on the detection results of the sensor.

[0168] As shown in FIG. 10, the controller 50 may receive an input selecting an excavation target to be excavated by the bucket 14. As shown in FIGS. 12 and 13, the relationship between the load mass and the attitude of the bucket 14 may be stored in advance for each excavation target. The operator can recognize the type of excavation target at the work site and select that type of excavation target. The operator can estimate the specific gravity of the excavation target based on the weather of the day, etc., and select an excavation target with that specific gravity. By referencing a table stored in advance for the selected excavation target and modifying the referenced table, the relationship between the load mass and the attitude of the bucket 14 can be obtained more accurately using the modified table.

[0169] 10, the controller 50 may store the corrected table. When performing work under similar conditions later, the controller 50 can operate the work machine 3 using the stored corrected table, in which case calibration to correct the table can be omitted.

[0170] 15, controller 50 may obtain the angle of repose of the excavation target to be excavated by bucket 14, and correct the table based on the obtained angle of repose. By correcting the relationship between the load mass and the attitude of bucket 14 based on the angle of repose of the excavation target, the relationship between the load mass and the attitude of bucket 14 can be obtained with even greater accuracy using the corrected table.

[0171] <Additional Notes> The above description includes the following additional features.

[0172] (Appendix 1) a work machine having a bucket at its tip; a controller that commands the operation of the work machine, The controller modifies the pre-stored relationship between the load mass, which is the mass of the load in the bucket, and the bucket attitude, based on the pre-stored relationship and the load mass at the acquired specific bucket attitude.

[0173] (Appendix 2) The work machine described in Appendix 1, wherein the controller corrects the relationship using a ratio between a load mass determined by the relationship when the bucket is in the one specific bucket position and the acquired load mass.

[0174] (Appendix 3) 3. The work machine of claim 1 or 2, wherein the controller uses the modified relationship to discharge the load from the bucket.

[0175] (Appendix 4) 4. The work machine according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the one particular bucket posture is a posture of the bucket at which a load mass is maximum.

[0176] (Appendix 5) 5. The work machine of claim 1, wherein the attitude of the bucket is defined by an angle of the bucket with respect to a ground surface.

[0177] (Appendix 6) 6. The work machine of any one of Supplementary Notes 1 to 5, wherein the controller receives an input selecting an excavation target to be excavated by the bucket.

[0178] (Appendix 7) 7. The work machine according to claim 6, wherein the relationship is stored for each of the excavation targets.

[0179] (Appendix 8) 8. The work machine according to any one of Supplementary Note 1 to Supplementary Note 7, wherein the controller acquires an angle of repose of an excavation target to be excavated by the bucket, and modifies the pre-stored relationship based on the angle of repose.

[0180] (Appendix 9) 9. The work machine of any one of Supplementary Notes 1 to 8, wherein the controller stores the modified relationship.

[0181] The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0182] 1 Wheel loader, 2 Body frame, 3 Work equipment, 4 Traveling device, 5 Cab, 9 Machine body, 14 Bucket, 14a Cutting edge, 14b Rear surface, 15 Boom, 16 Bell crank, 18 Boom cylinder, 19 Bucket cylinder, 21 Boom foot pin, 22 Bucket pin, 31b, 31h, 32b, 32h Pressure sensor, 33, 34 Potentiometer, 35, 36 Stroke sensor, 39 Imaging device, 40 Angle sensor, 50 Controller, 51 Input unit, 52 Display unit, 100 Excavation target, 500 Memory unit, 501 Boom cylinder thrust calculation unit, 502 Hydraulic transmission efficiency calculation unit, 503 Dimension value calculation unit, 505 Bucket ground angle calculation unit, 508 Target load mass calculation unit, 509 Load mass calculation unit, 510 Tip-off automatic control unit, 511 Auto tip-off start determination unit, 512 auto tip-off control unit, 513 auto tip-off end determination unit, 520 normal calibration screen, 530 table calibration unit.

Claims

1. a work machine having a bucket at its tip; a controller that commands the operation of the work machine, The controller modifies the pre-stored relationship between the load mass, which is the mass of the load in the bucket, and the bucket attitude, based on the pre-stored relationship and the load mass at the acquired specific bucket attitude.

2. The work machine according to claim 1 , wherein the controller modifies the relationship using a ratio between a load mass determined by the relationship when the bucket is in the one specific bucket position and the acquired load mass.

3. The work machine of claim 1 , wherein the controller utilizes the modified relationship to cause the bucket to empty the load.

4. The work machine according to claim 1 , wherein the one particular bucket attitude is an attitude of the bucket at which a load mass is at its maximum.

5. The work machine of claim 1 , wherein the bucket attitude is defined by an angle of the bucket relative to the ground.

6. The work machine of claim 1 , wherein the controller receives an input selecting an excavation target to be excavated by the bucket.

7. The work machine according to claim 6 , wherein the relationship is stored for each of the excavation targets.

8. The work machine according to claim 1 , wherein the controller acquires an angle of repose of an object to be excavated by the bucket, and modifies the pre-stored relationship based on the angle of repose.

9. The work machine of claim 1 , wherein the controller stores the modified relationship.

10. a work machine having a bucket at its tip; a controller that commands the operation of the work machine, The controller Modifying the pre-stored relationship between the load mass, which is the mass of the load in the bucket, and the attitude of the bucket based on the pre-stored relationship and the load mass at the acquired specific bucket attitude, or After the load mass is maximized, the load is discharged from the bucket, and the load mass and the attitude of the bucket are acquired during the discharge of the load, thereby correcting the pre-stored relationship; A work machine that selectively performs any one of the above.

11. a work machine including a work implement having a bucket at its tip; a controller that commands the operation of the work machine, The controller modifies the pre-stored relationship between a load mass, which is the mass of a load in the bucket, and the bucket attitude, based on the pre-stored relationship and the load mass at one specific bucket attitude obtained.

12. Putting a bucket at the tip of the work machine in one specific position; acquiring a load mass, which is a mass of the load in the bucket when the bucket is in the specific attitude; and correcting a pre-stored relationship between the load mass and the attitude of the bucket based on the acquired load mass.

Images