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

Abstract

To provide a work machine capable of automatically performing chipping-off in a short time.SOLUTION: A work machine includes a vehicle body, machinery fixed to the vehicle body, having a bucket at the tip, and a controller that commands operations of the machinery. The controller moves the bucket in a damping direction after an excavation operation for excavating an excavation object, toward a specific bucket posture determined by a relation between the mass of load that is the mass of excavation object in the bucket and the posture of the bucket and a target mass of load as target value of the mass of load. The specific bucket posture is a posture tilted back from the bucket posture when the excavation object with the target mass of load is accommodated in the bucket.SELECTED DRAWING: Figure 8

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 an operation in which excess load in a bucket is dropped from the bucket. Tipping off is performed, for example, to adjust the amount of load from a work machine to a transport machine and prevent overloading of the transport machine traveling on a specified travel path. U.S. Patent Application Publication No. 2020 / 0263384 (Patent Document 1) describes a tipping off operation in which a tipping off threshold is determined based on the amount of load in the bucket, a single dump operation is performed to spill the load until the tipping off threshold is reached, and then dumping and tilting are repeated at a low speed to further spill the load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2020 / 0263384 Summary of the Invention [Problem to be solved by the invention]

[0004] If tip-off can be performed in a short time, the productivity of work performed by the work machine can be improved.

[0005] The present disclosure proposes a work machine, a system including a work machine, and a method for controlling a work machine, which are capable of automatically performing tip-off in a short period of time. [Means for solving the problem]

[0006] A work machine according to one aspect of the present disclosure includes a vehicle body, a work implement attached to the vehicle body and having a bucket at its tip, and a controller that commands operation of the work implement. After an excavation operation in which the bucket excavates an excavation target, the controller moves the bucket in the dump direction toward a specific bucket attitude determined by a relationship between a load mass, which is the mass of the excavation target in the bucket, and the bucket attitude, and a target load mass, which is a target value for the load mass. The specific bucket attitude is an attitude that is tilted back more than the bucket attitude when an excavation target of the target load mass is contained in the bucket.

[0007] A system according to one aspect of the present disclosure includes a work machine. The work machine includes a vehicle body and a work implement attached to the vehicle body and having a bucket at its tip. The system also includes a controller that commands operation of the work implement. After an excavation operation in which the bucket excavates an excavation target, the controller moves the bucket in the dump direction toward a specific bucket attitude determined by the relationship between the load mass, which is the mass of the excavation target in the bucket, the attitude of the bucket, and a target load mass, which is a target value for the load mass. The specific bucket attitude is an attitude that is tilted back more than the bucket attitude when an excavation target of the target load mass is contained in the bucket.

[0008] A method for controlling a work machine according to one aspect of the present disclosure includes the following steps. The first step is to perform excavation work by excavating an excavation target with a bucket at the tip of the work machine. The second step is to determine a specific bucket attitude based on the relationship between the load mass, which is the mass of the excavation target in the bucket, and the bucket attitude, and a target load mass, which is a target value for the load mass. The specific bucket attitude is an attitude that is tilted back more than the bucket attitude when an excavation target of the target load mass is contained in the bucket. The third step is to move the bucket in the dump direction after the excavation work is completed, so as to aim for the specific bucket attitude. [Effects of the Invention]

[0009] According to the present disclosure, tip-off can be performed automatically in a short time. [Brief explanation of the drawings]

[0010] [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. 1 is a schematic diagram showing an overview of auto tip-off according to an embodiment. [Figure 8] FIG. 10 is a schematic diagram showing the processing content in the control of Step 1. [Figure 9] FIG. 10 is a schematic diagram showing the processing content in the control of Step 2. [Figure 10] 10 is a graph showing the speed of the bucket in Step 2. [Figure 11] FIG. 10 is a schematic diagram showing the processing content in the control of Step 3. [Figure 12] 10 is a graph showing the rate of decrease in cargo mass in Step 3. [Figure 13] 10 is a graph showing the speed of the bucket during auto tip-off execution. [Figure 14] FIG. 10 is a flowchart illustrating a process flow of full tilt control. [Figure 15] FIG. 10 is a flowchart illustrating another example of the processing flow of the auto tip-off control. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] <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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] <Calculating cargo mass> FIG. 2 is a diagram for explaining the dimensions of each part of the work implement 3 and the balance of four moments.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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).

[0049]

number

[0050] In equation (1), g is the acceleration due to gravity. The same applies to equations (2) and (4) described below.

[0051] 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).

[0052]

number

[0053] 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.

[0054] Boom cylinder 18 thrust F cyl Moment c by Wload is expressed by the following equation (3).

[0055]

number

[0056] In equation (3), η is the hydraulic transmission efficiency of the boom 15.

[0057] Moment d due to reaction force F4 of bucket 14 Wload is expressed by the following equation (4).

[0058]

number

[0059] 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.

[0060] 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.

[0061]

number

[0062] From equation (5), the cargo mass W load The result is the following equation (6): load is included in equations (1) and (4).

[0063]

number

[0064] <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 the 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] <Functional configuration> Next, a description will be given of the functional configuration of the wheel loader 1. In particular, a functional block of the controller 50 that automatically executes tipping off (auto-tip off) after excavation work in the wheel loader 1 shown in Fig. 1 will be described using Fig. 4.

[0070] 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.

[0071] 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 cargo mass calculation unit 508, a cargo mass calculation unit 509, and an automatic tip-off control unit 510. 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.

[0072] 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.

[0073] 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.

[0074] 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).

[0075] 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.

[0076] 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.

[0077] 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).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The target load mass calculation unit 508 calculates the target soil volume, which is the target value for the mass of the load to be loaded in the bucket 14 at the end of tip-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 soil volume corresponds to an example of a "target load mass," which is the target value for the load mass for auto tip-off. 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.

[0082] The cargo mass calculation unit 509 calculates each mass Wg bucket ,W we , correction coefficient β, and thrust F cyl The cargo mass is periodically calculated using the above-mentioned formulas (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, and the auto tip-off end determination unit 513.

[0083] 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.

[0084] <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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] Returning to FIG. 5, if it is determined in step S6 that the target soil volume is smaller 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 greater than the target value for the load mass in the bucket 14 (target load mass) (YES in step S6), then in step S7, the controller 50 (auto-tip-off control unit 512) starts auto-tip-off. The controller 50 starts driving the bucket cylinder 19, which moves the bucket 14 in the dumping direction. The operation of raising the boom 15, which was started in step S5, continues during auto-tip-off.

[0102] 7 is a schematic diagram showing an overview of auto tip-off according to an embodiment. In the auto tip-off according to the embodiment, of the three steps, Step 1, Step 2, and Step 3, the process of Step 1 is executed first, and then either or both of Step 2 and Step 3 are executed.

[0103] As shown in Figure 7, in the processing of Step 1, control is executed to dump soil roughly in accordance with the target soil volume. In the processing of Step 2, the speed of the bucket 14 is determined based on the instantaneous load, which is the current load mass in the bucket 14, and the target soil volume, which is the target value for the load mass. Specifically, control is executed to move the bucket 14 in the dumping direction at a speed determined by the magnitude of the difference between the instantaneous load and the target soil volume. In the processing of Step 3, control is executed to move the bucket 14 so that the rate at which the instantaneous load, which is the current load mass in the bucket 14, decreases is constant.

[0104] In step S8, the controller 50 (auto tip-off control unit 512) performs the control of Step 1. Fig. 8 is a schematic diagram showing the processing content in the control of Step 1.

[0105] As shown in FIG. 8, in the control of Step 1, the load mass and the attitude of the bucket 14 (specifically, the bucket ground angle θ B) and the target bucket ground angle θ T The table T1 shown in FIG. 8 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. For example, the table T1 is calculated by setting the load mass in the bucket 14 to a maximum, discharging the load from the bucket 14, and then calculating the relationship between the load mass in the bucket 14 and the attitude of the bucket 14 (bucket ground angle θ B ) and can be created by obtaining the

[0106] 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 the value of is negative, the back surface 14b of the bucket 14 is inclined with respect to the ground surface G so that the back surface 14b is positioned lower as it approaches the cutting edge 14a.

[0107] The curve shown by the solid line in table T1 is the bucket ground angle θ B The curve is a smoothed result of determining the amount of soil in the bucket 14 for each value of . The dashed curve in table T1 is a curve obtained by moving the solid curve upward in parallel. The dashed curve shows the attitude of the bucket 14 in the tilt direction, with a margin taken into account for the attitude of the bucket 14 when a specific amount of cargo is stored in the bucket 14.

[0108] In the auto tip-off mode, 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 determines the specific bucket attitude (target bucket ground angle θ) based on the calculated target soil volume and the dashed line shown in table T1. TThe controller 50 determines the target bucket ground angle θ using the dashed line instead of the solid line shown in table T1. T The following is established.

[0109] The controller 50 determines the bucket ground angle θ when the target soil volume is contained in the bucket 14. B Bucket ground angle θ B The target bucket ground angle θ T The controller 50 determines the bucket ground angle θ when the target soil volume is accommodated in the bucket 14. B The bucket ground angle θ is greater than B The target bucket ground angle θ T The controller 50 determines the bucket ground angle θ when the bucket 14 is in a tilted position relative to the position of the bucket 14 when the target soil volume is accommodated in the bucket 14. B The target bucket ground angle θ T The controller 50 determines the bucket ground angle θ when the bucket 14 is tilted back from the attitude when the target soil volume is accommodated in the bucket 14. B The target bucket ground angle θ T Here, the tilted back posture is defined as the posture where the bucket ground angle θ B This means that the posture has a large value.

[0110] The controller 50 operates the bucket 14 in the dump direction toward a specific bucket attitude, and discharges the excavated object in the bucket 14 from the bucket 14. In this way, the controller 50 reduces the load mass in the bucket 14. The controller 50 operates the bucket 14 in the dump direction, and controls the bucket ground angle θ B The bucket's ground angle θ is aimed at T Get closer to.

[0111] In the control of Step 1, 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 a specific bucket attitude based on the target soil volume (target load mass). In table T2 shown in FIG. 8, 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.

[0112] 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.

[0113] Table T2 shows an example of a target bucket flow rate in the control of Step 1 of auto-tip-off. When auto-tip-off is performed, 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 oil chamber on the head side of the bucket cylinder 19 is zero. When the target bucket flow rate is minus 100%, the amount of hydraulic oil flowing into the oil chamber on the head side 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.

[0114] 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 Tbecomes 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.

[0115] 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 the control variable for Step 1. 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.

[0116] 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 T The 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 control in step S1.

[0117] Current bucket ground angle θ B The target bucket angle θ T (YES in the determination of step S9), the controller 50 ends the control of step 1 and moves to the control of step 2 or step 3. B Based on this, control is switched from Step 1 to Step 2 or Step 3.

[0118] In step S10, the controller 50 (auto tip-off control unit 512) performs control of Step 2. Fig. 9 is a schematic diagram showing the processing content in the control of Step 2.

[0119] As shown in Figure 9, in the control of Step 2, the controller 50 performs a calculation to determine the difference between the current cargo mass and the target soil volume. The controller 50 determines the difference obtained by subtracting the target soil volume from the current cargo mass as the current cargo mass difference u. The controller 50 calculates the square of the absolute value of the current cargo mass difference u and multiplies it by a proportionality coefficient k2 to convert the cargo mass difference u to the target bucket flow rate. The cargo mass difference u is squared in order to emphasize the difference in cargo mass.

[0120] The square of the absolute value of the load mass difference u is a positive value, and the proportionality coefficient k2 is a negative value, so the target bucket flow rate is a negative value. The target bucket flow rate is a value that determines the speed of the bucket 14 moving in the dumping direction. The target bucket flow rate is converted into a flow rate / voltage to find the bucket lever voltage. The bucket cylinder 19 is controlled using this found bucket lever voltage as the control amount in Step 2.

[0121] Fig. 10 is a graph showing the speed of the bucket 14 in Step 2. The horizontal axis of the graph shown in Fig. 10 represents the current load mass difference u, and the vertical axis represents the speed of the bucket 14 moving in the dump direction. The speed of the bucket 14 in Step 2 is determined by the current load mass and the target load mass (target soil volume). More specifically, the speed of the bucket 14 in Step 2 is determined by the magnitude of the difference between the current load mass and the target load mass.

[0122] As shown in Figure 10, when the current load mass difference u is large, the dumping speed of the bucket 14 is high, and when the current load mass difference u is small, the dumping speed of the bucket 14 is low. As the current load mass is large, the load mass difference u becomes large and the dumping speed of the bucket 14 becomes high. During the processing of Step 2, the load is discharged from the bucket 14, the load mass decreases, and the load mass difference u gradually becomes smaller. As time passes after the control of Step 2 is started, the dumping speed of the bucket 14 gradually decreases.

[0123] Returning to FIG. 5, in step S11, the controller 50 (auto tip-off control unit 512) compares the current load mass with a predetermined threshold determined by the target soil volume. In this embodiment, the threshold is the target soil volume plus mass α. Mass α is set in advance and stored in the memory unit 500. Mass α is set to a relatively small value. Mass α may be a value less than 0.5 ton, for example. The controller 50 compares the current load mass with (target soil volume + α). The controller 50 determines whether the current load mass is smaller than (target soil volume + α). By setting the target soil volume plus mass α as the threshold, the load in the bucket 14 is prevented from being reduced too much during tip-off.

[0124] If the current cargo mass is equal to or greater than the threshold value (NO in step S11), the process proceeds to step S12. In step S12, the controller 50 (auto-tip-off control unit 512) calculates the current bucket ground angle θ B Determine whether the bucket ground angle θ is less than 0°. B The attitude of the bucket 14 when the angle θ is 0° corresponds to an example of the "second specific bucket attitude." The bucket ground angle θ when the bucket 14 assumes the second specific bucket attitude is B is the bucket ground angle θ when the bucket 14 takes a specific bucket posture. B (Aiming bucket ground angle θ T 8). The bucket ground angle θ when the bucket 14 assumes the second specific bucket posture is different from the bucket ground angle θ when the bucket 14 assumes the second specific bucket posture. Bis not limited to 0° and may be another angle.

[0125] In the control of Step 2, the bucket 14 moves in the dump direction and approaches the second specific bucket attitude. B If the current bucket ground angle θ is equal to or greater than 0° (NO in step S12), the process returns to step S10, and the controller 50 continues the control in step 2. B If the bucket ground angle θ is smaller than 0° (YES in the determination of step S12), the controller 50 ends the control of step 2 and moves to the control of step 3. B Based on this, control is switched from Step 2 to Step 3.

[0126] In step S13, the controller 50 (auto tip-off control unit 512) performs control of Step 3. Fig. 11 is a schematic diagram showing the processing content of the control of Step 3.

[0127] 11, in the control of Step 3, the controller 50 performs a calculation to determine the difference between the current cargo mass and the previously calculated cargo mass. The controller 50 determines the difference by subtracting the immediately previous cargo mass from the current cargo mass. The controller 50 calculates the current rate of decrease of the cargo mass by dividing the determined difference by the elapsed time from when the immediately previous cargo mass was obtained to the present.

[0128] The controller 50 further performs a calculation to determine the difference between the current cargo mass reduction rate and the target cargo mass reduction rate. The target cargo mass reduction rate is set in advance. The controller 50 calculates the difference by subtracting the target cargo mass reduction rate from the current cargo mass reduction rate, and sets the calculated difference as the current speed difference. The controller 50 multiplies the current speed difference by a proportionality coefficient k3 to convert the speed difference into a bucket flow rate. The proportionality coefficient k3 is a positive value.

[0129] A positive current speed difference indicates that the current load mass reduction rate is greater than the target load mass reduction rate, and that the speed at which the load in the bucket 14 is being discharged from the bucket 14 is too high. A negative current speed difference indicates that the current load mass reduction rate is less than the target load mass reduction rate, and that the speed at which the load in the bucket 14 is being discharged from the bucket 14 is too low, or that the load in the bucket 14 has not been discharged from the bucket 14.

[0130] The controller 50 calculates the target bucket flow rate by adding the bucket flow rate determined from the current speed difference to the previously determined target bucket flow rate. Because the bucket 14 is performing a dump operation, the previous target bucket flow rate is a negative value. If the current speed difference is positive, the target bucket flow rate calculated by this calculation will be a negative value with a smaller absolute value than the previous target bucket flow rate. The speed at which the bucket 14 is moved in the dump direction decreases. If the current speed difference is negative, the target bucket flow rate calculated by this calculation will be a negative value with a larger absolute value than the previous target bucket flow rate. The speed at which the bucket 14 is moved in the dump direction increases.

[0131] The target bucket flow rate is converted into a flow rate / voltage to obtain a bucket lever voltage, which is used as a control variable in Step 3 to control the bucket cylinder 19.

[0132] FIG. 12 is a graph showing the rate of decrease in cargo mass in Step 3. The horizontal axis of the graph shown in FIG. 12 represents the elapsed time since control in Step 3 was started. The vertical axis of the graph represents cargo mass. In Step 3, the controller 50 operates the bucket 14 so that the rate of decrease in cargo mass becomes constant. The graph shown in FIG. 12 is linear, with a constant slope. After control in Step 3 is started, the amount of decrease in cargo mass per unit time becomes constant.

[0133] Figure 13 is a graph showing the speed of the bucket 14 during execution of auto tip-off. The horizontal axis of the graph shown in Figure 13 represents the elapsed time since auto tip-off began. The vertical axis of the graph represents the speed of the bucket 14 moving in the dump direction. Figure 13 shows an example in which Step 1 control is performed from time 0 to time T12, Step 2 control is performed from time T12 to time T23, and Step 3 control is performed from time T23 onwards.

[0134] In the control of Step 1, the controller 50 moves the bucket 14 in the dumping direction at a constant speed. As time passes after the control of Step 2 is started, the dumping speed of the bucket 14 gradually decreases. When the control shifts to Step 3, the dumping speed of the bucket 14 further decreases. The controller 50 makes the speed of the bucket 14 in Step 2 slower than the speed of the bucket 14 in Step 1. The controller 50 makes the speed of the bucket 14 in Step 3 slower than the minimum speed of the bucket 14 in Step 2. The controller 50 makes the speed of the bucket 14 in Step 3 slower than the speed of the bucket 14 in Step 1.

[0135] Returning to FIG. 5, in step S14, the controller 50 (auto tip-off completion determination unit 513) determines whether the current load mass is smaller than (target soil volume + α). The determination in step S14 is performed in the same manner as in step S11. If the current load mass is equal to or greater than the threshold value (NO in the determination in step S14), the process returns to step S13, and the controller 50 continues the control in step 3.

[0136] If the determination in step S11 or step S14 is that the current cargo mass is smaller than the threshold value (YES in step S11 or YES in step S14), controller 50 determines that the cargo mass in bucket 14 has been reduced. Controller 50 ends control of moving bucket 14 in the dump direction. In step S15, controller 50 performs full tilt control, moving bucket 14 in the tilt direction up to the full tilt state. FIG. 14 is a flow diagram for explaining the flow of processing for full tilt control.

[0137] In step S151, the controller 50 ends tip-off. The controller 50 stops the movement of the bucket 14 in the dump direction to prevent the load mass in the bucket 14 from decreasing any further.

[0138] In step S152, the controller 50 holds the boom angle at the end of tip-off. The operation of raising the boom 15, which was started in step S5 shown in FIG. 5, is maintained while the bucket 14 is operated by the control of steps 1, 2, and 3, and continues up to step S152. In step S152, the controller 50 stops the operation of raising the boom 15. Thereafter, the controller 50 does not operate the boom 15. The controller 50 holds the boom angle when the boom 15 was stopped.

[0139] In step S153, the controller 50 determines the target bell crank angle c. The target bell crank angle c is the bell crank angle θ2 when the bucket 14 is in a fully tilted state. The target bell crank angle c changes depending on the boom angle. A table or graph showing the relationship between the boom angle and the target bell crank angle c is stored in the memory unit 500. The controller 50 applies the boom angle when the boom 15 was stopped in the previous step S152 to the relationship between the boom angle and the target bell crank angle c to determine the target bell crank angle c.

[0140] In step S154, the controller 50 sets a bucket tilt flow rate. The bucket tilt flow rate is the flow rate of hydraulic oil supplied to the bucket cylinder 19 to move the bucket 14 in the tilt direction. The bucket tilt flow rate is set in the range from 0% to 100%, and the larger the bucket tilt flow rate, the faster the speed of the bucket 14 moving in the tilt direction. In step S154, the controller 50 sets a set value for the bucket tilt flow rate to FR1. The set value FR1 is set to a relatively large value. The set value FR1 is set to a value close to 100%. The set value FR1 may be, for example, a value of 80% or more.

[0141] The controller 50 supplies hydraulic oil to the oil chamber on the bottom side of the bucket cylinder 19 so that the hydraulic oil corresponds to the bucket tilt flow rate set value FR1, thereby increasing the length of the bucket cylinder 19. This increases the bell crank angle θ2, and the bucket 14 moves in the tilt direction. The bucket 14 moves in the tilt direction at high speed.

[0142] In step S155, controller 50 compares the current bell crank angle θ2 with the angle obtained by subtracting angle β from target bell crank angle c. Angle β is set in advance and stored in memory unit 500. Angle β is set to a relatively small angle. For example, angle β may be an angle less than 10°. Controller 50 compares current bell crank angle θ2 with angle (c-β). Controller 50 determines whether or not current bell crank angle θ2 is greater than angle (c-β). The attitude of bucket 14 when bell crank angle θ2 is angle (c-β) corresponds to an example of a "predetermined bucket attitude."

[0143] If the current bell crank angle θ2 is equal to or less than the angle (c−β) (NO in step S155), the process returns to step S154, and the process of moving the bucket 14 in the tilt direction in step S154 and the determination in step S155 are repeated.

[0144] If it is determined that the current bell crank angle θ2 has become larger than the angle (c−β) due to continued movement of the bucket 14 in the tilt direction (YES in step S155), then in step S156 the controller 50 changes the set value of the bucket tilt flow rate. In step S156, the controller 50 sets the set value of the bucket tilt flow rate to a value different from FR1. The controller 50 sets the set value of the bucket tilt flow rate to FR2, which is smaller than FR1. The set value FR2 is set to a relatively small value. The set value FR2 is set to a value close to 0%. The set value FR2 may be, for example, a value equal to or less than 15%.

[0145] The controller 50 supplies hydraulic oil to the oil chamber on the bottom side of the bucket cylinder 19 so that the bucket tilt flow rate becomes the set value FR2. The length of the bucket cylinder 19 increases, the bell crank angle θ2 increases, and the bucket 14 moves in the tilt direction. By decreasing the set value of the bucket tilt flow rate, the rate at which the length of the bucket cylinder 19 increases decreases. The speed of the bucket 14 moving in the tilt direction decreases. The bucket 14 moves in the tilt direction at a low speed toward a fully tilted attitude. The controller 50 makes the speed of the bucket 14 after the bell crank angle θ2 becomes greater than angle (c-β) slower than the speed of the bucket 14 when the bell crank angle θ2 is equal to or less than angle (c-β).

[0146] In step S157, the controller 50 compares the current bell crank angle θ2 with the target bell crank angle c. The controller 50 determines whether the current bell crank angle θ2 is greater than the target bell crank angle c.

[0147] If the current bell crank angle θ2 is equal to or less than the target bell crank angle c (NO in step S157), the process returns to step S156, and the process of moving the bucket 14 in the tilt direction in step S156 and the determination in step S157 are repeated.

[0148] When it is determined that the current bell crank angle θ2 has reached the target bell crank angle c by continuing the movement of the bucket 14 in the tilt direction (YES in step S157), the controller 50 ends the full tilt control in step S158. Returning to FIG. 5, in step S16, the controller 50 ends the auto tip-off.

[0149] 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 the 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 S16, and the controller 50 ends auto tip-off.

[0150] 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.

[0151] In the auto tip-off control process shown in FIG. 5, the controller 50 moves to control of Step 2 after control of Step 1, and after Step 2, moves to control of Step 3, or ends tip-off as is, but is not limited to this example. Control of Step 2 does not necessarily have to be performed. Control of Step 3 may be executed after control of Step 1, skipping control of Step 2. Processing may also move directly from control of Step 1 to control of Step 3. FIG. 15 is a flow chart for explaining another example of the flow of processing of auto tip-off control. Differences between the processing shown in FIG. 15 and the processing shown in FIG. 5 will be described below.

[0152] In the process shown in FIG. 15, the current bucket ground angle θ B The target bucket angle θT If it is equal to or greater than this (NO in step S9), the process proceeds to step S21. In step S21, the controller 50 calculates the current bucket ground angle θ B It is determined whether or not the angle .theta..times ...

[0153] In the judgment of step S21, the current bucket ground angle θ B If the current bucket ground angle θ is equal to or greater than 0° (NO in step S21), the process returns to step S8, and the controller 50 continues the control in step 1. B If is smaller than 0° (YES in the determination in step S21), the controller 50 ends the control of step 1 and moves to the control of step 3. The process proceeds to step S13 via a connector A, and in step S13, the controller 50 performs the control of step 3.

[0154] Target bucket ground angle θ T However, there are cases where the angle is set to be smaller than 0°. With reference to the broken line shown in table T1 in FIG. 8, if the target soil volume is 2 tons, for example, the target bucket ground angle θ T In this case, the bucket 14 is moved in the dump direction to reduce the bucket ground angle θ B As the bucket ground angle θ decreases, B The target bucket angle θ T Before reaching (-20°), the current bucket ground angle θ B In this case, as shown in Fig. 15, the control of Step 2 in step S10 is not performed, and the process moves directly from the control of Step 1 to the control of Step 3.

[0155] <Action and effect> The characteristic configuration and effects of this embodiment are summarized as follows.

[0156] As shown in FIG. 8, the auto tip-off control unit 512 of the controller 50 controls the load mass and the bucket ground angle θ B Using table T1, which shows the relationship between the target bucket ground angle θ T The auto tip-off control unit 512 determines the target bucket ground angle θ T The bucket 14 is moved in the dump direction toward the target.

[0157] This bucket angle θ B The relationship between the load mass in the bucket 14 and the target load mass is determined in advance. A table T1 showing this relationship is stored in the storage unit 500. By applying the target load mass to the table T1, the target bucket ground angle θ T Determine the target bucket ground angle θ T The speed at which the bucket 14 is dumped is increased until the bucket 14 reaches the target bucket ground angle θ . By setting a speed-up range where the load in the bucket 14 can be roughly dumped without any adverse effect, the controller 50 can adjust the bucket 14 to the target bucket ground angle θ . T This shortens the time it takes to move the bucket 14 toward the target position, thereby shortening the time it takes to unload the load from the bucket 14. This allows tip-off to be performed automatically in a short amount of time.

[0158] As shown in FIG. 8, the bucket ground angle θ when the bucket 14 is tilted back from the attitude when the excavation target of the target load mass is accommodated in the bucket 14 is B The target bucket ground angle θ T The target bucket ground angle θ T The speed of the bucket 14 is increased until it reaches the target bucket ground angle θ T The speed of the bucket 14 is reduced after reaching the predetermined speed. By doing so, tip-off can be performed automatically with high accuracy in a short time.

[0159] As shown in FIG. 5, the auto-tip-off control unit 512 of the controller 50 may move the bucket 14 in the dump direction when the load mass after the excavation operation is greater than the target load mass. If the load mass after the excavation operation is equal to or less than the target load mass, tip-off, which discharges the load in the bucket 14, may not be performed. The controller 50 determines whether it is necessary to discharge the load in the bucket 14 and adjust the load mass, and if the load mass is the target load mass and no adjustment of the load mass is necessary, it controls not to perform tip-off. This makes it possible to prevent the load in the bucket 14 from being reduced too much.

[0160] As shown in FIG. 13, the auto tip-off control section 512 of the controller 50 controls the target bucket ground angle θ T Alternatively, the bucket 14 may be operated at a constant speed toward the target point. If an attempt is made to set the speed of the bucket 14 based on the load mass calculated while the instantaneous value of the load mass is pulsating, the operation of the bucket 14 may become unstable. By controlling the bucket 14 to operate at a constant speed, the bucket 14 can be operated stably, and the productivity of the excavation and loading work can be stabilized. By setting the speed of the bucket 14 to a sufficiently large constant speed, the controller 50 can adjust the bucket 14 to the target bucket ground angle θ T Therefore, the time required for moving the object toward the target can be reliably shortened.

[0161] As shown in FIG. 8, the auto tip-off control section 512 of the controller 50 controls the target bucket ground angle θ T The speed of the bucket 14 moving toward the target load mass may be determined based on the target load mass. When the target load mass is small, the movement distance of the bucket 14 until the load mass in the bucket 14 reaches the target load mass increases. By controlling the bucket 14 to perform the dump operation at a higher speed when the target load mass is small, it is possible to prevent the time required for tip-off from becoming longer depending on the target load mass.

[0162] As shown in FIGS. 5, 8 to 10, the auto tip-off control unit 512 of the controller 50 controls the target bucket ground angle θT After reaching the target bucket angle θ, the bucket 14 may be continuously moved in the dump direction. T The bucket 14 is dumped at high speed until it reaches the target bucket ground angle θ T After reaching the target load mass, the bucket 14 is dumped so as to accurately reduce the load mass to the target load mass. This allows automatic tip-off to be performed with high accuracy in a short time.

[0163] As shown in FIG. 13, the auto tip-off control section 512 of the controller 50 controls the target bucket ground angle θ T The speed of the bucket 14 after reaching the target bucket ground angle θ T The speed of the bucket 14 may be smaller than the speed at which the bucket 14 reaches the target ground angle θ. T The bucket 14 is dumped at high speed until it reaches the target bucket ground angle θ T After reaching the target load mass, the bucket 14 is dumped at a slower speed, and the load mass is accurately reduced to the target load mass. This allows for automatic tip-off with high accuracy in a short period of time.

[0164] As shown in FIGS. 9 and 10, the auto tip-off control section 512 of the controller 50 controls the target bucket ground angle θ T The speed of the bucket 14 after reaching the target load mass may be determined based on the current load mass and the target load mass. By determining the speed of the bucket 14 in this manner, the bucket 14 can be dumped so as to accurately reduce the load mass to the target load mass.

[0165] As shown in FIGS. 9 and 10, the auto tip-off control section 512 of the controller 50 controls the target bucket ground angle θ T The speed of the bucket 14 after reaching the target load mass may be determined based on the magnitude of the difference between the current load mass and the target load mass. By reducing the speed of the bucket 14 as the current load mass approaches the target load mass, the bucket 14 can be dumped so as to accurately reduce the load mass to the target load mass.

[0166] As shown in FIGS. 5 and 11, the auto tip-off control unit 512 of the controller 50 determines the current bucket ground angle θ B After the bucket ground angle θ becomes smaller than 0°, the bucket 14 may be continuously moved in the dump direction. B When the bucket ground angle θ is smaller than 0°, the bucket 14 is in a position that actively drops the load in the bucket 14 from the cutting edge 14a. B After the angle becomes smaller than 0°, the bucket 14 is dumped so as to accurately reduce the load mass to the target load mass. This allows for automatic and highly accurate tip-off.

[0167] As shown in FIG. 13, the auto tip-off control unit 512 of the controller 50 controls the bucket to ground angle θ B The speed of the bucket 14 after the bucket ground angle θ becomes smaller than 0° is defined as B The speed of the bucket 14 may be slower than that when the bucket ground angle θ is 0° or more. B After the angle becomes smaller than 0°, the bucket 14 is dumped at a slower speed to accurately reduce the load mass to the target load mass. This allows for automatic and highly accurate tip-off.

[0168] As shown in FIG. 15, the auto tip-off control section 512 of the controller 50 controls the target bucket ground angle θ T The current bucket ground angle θ B becomes smaller than 0°, the bucket 14 continues to move in the dump direction, and the bucket ground angle θ B The speed of the bucket 14 after the bucket ground angle θ becomes smaller than 0° is defined as B The speed of the bucket 14 may be slower than that when the bucket ground angle θ is 0° or more. B When the bucket 14 is at or above 0°, the bucket 14 is dumped at high speed, and the bucket ground angle θ BAfter the angle becomes smaller than 0°, the bucket 14 is dumped at a slower speed to accurately reduce the load mass to the target load mass. This allows for automatic tip-off with high accuracy in a short period of time.

[0169] As shown in FIG. 12, the auto tip-off control unit 512 of the controller 50 controls the bucket to ground angle θ B After the bucket ground angle θ becomes smaller than 0°, the bucket 14 may be operated so that the rate of decrease in the load mass becomes constant. B When the bucket ground angle θ is less than 0°, the bucket 14 is in a position where the load falls from the cutting edge 14a. B By decreasing the speed of the bucket 14 as the absolute value of θ increases, the rate at which the load mass decreases can be kept constant. In this way, the end of tipping-off can be determined with higher accuracy. The smaller the target load mass, the more accurate tipping-off can be performed automatically with this control.

[0170] 5 and 14, the auto tip-off control unit 512 of the controller 50 may raise the boom 15 while moving the bucket 14 in the dumping direction. By calculating the load mass while the boom 15 is being raised, the load mass can be calculated more accurately.

[0171] As shown in FIGS. 5 and 14 , when the auto tip-off control unit 512 of the controller 50 determines that the load mass in the bucket 14 has been reduced, it moves the bucket 14 in the tilt direction. The load mass is reduced by causing the load in the bucket 14 to fall from the cutting edge 14a. During the operation of reducing the load mass, the load in the bucket 14 is biased toward the front side (toward the cutting edge 14a). By moving the bucket 14 in the tilt direction once the load mass in the bucket 14 has been reduced, the load in the bucket 14 can be moved rearward, improving the state of the load in the bucket 14. This makes it possible to prevent the load from spilling from the bucket 14 when the wheel loader 1 travels after tip-off.

[0172] 5 and 14, the auto tip-off control unit 512 of the controller 50 may perform full tilt control to move the bucket 14 in the tilt direction up to the full tilt state. Referring to FIG. 1, when the bucket 14 is in the full tilt state, the bucket ground angle θ B takes a positive value, and the back surface 14b of the bucket 14 is inclined with respect to the ground surface G so as to approach the ground surface G as it moves away from the cutting edge 14a, and the cutting edge 14a of the bucket 14 is positioned above the bucket pin 22. By placing the bucket 14 in a fully tilted state, the load in the bucket 14 can be reliably moved rearward, and the state of the load in the bucket 14 can be improved.

[0173] 14, the auto tip-off control unit 512 of the controller 50 may move the bucket 14 in the tilt direction at at least two different speeds. By moving the bucket 14 in the tilt direction at high speed, it is possible to reliably improve the shape of the contents in the bucket 14. By moving the bucket 14 at a low speed, it is possible to reduce the change in speed when the bucket 14 stops, thereby reducing the impact.

[0174] As shown in Fig. 14, the auto tip-off control unit 512 of the controller 50 may set the speed of the bucket 14 after the bell crank angle θ2 reaches the angle (c-β) to be slower than the speed of the bucket 14 before the bell crank angle θ2 reaches the angle (c-β). By moving the bucket 14 in the tilt direction at high speed until the bell crank angle θ2 reaches the angle (c-β), it is possible to reliably improve the shape of the load in the bucket 14. By moving the bucket 14 in the tilt direction at low speed after the bell crank angle θ2 reaches the angle (c-β), it is possible to reduce the impact when the bucket 14 stops.

[0175] As shown in FIG. 5 , the auto tip-off control unit 512 of the controller 50 may operate the bucket 14 in the dump direction to reduce the load mass in the bucket 14. By operating the bucket 14 in the dump direction, the load in the bucket 14 falls from the cutting edge 14a, reducing the load mass. Operating the bucket 14 in the dump direction causes the load in the bucket 14 to be biased toward the cutting edge 14a. After the load mass in the bucket 14 has been reduced, operating the bucket 14 in the tilt direction can move the load in the bucket 14 rearward, improving the state of the load in the bucket 14.

[0176] 5, the auto tip-off completion determination unit 513 of the controller 50 may determine that the load mass reduction has finished when the current load mass reaches a threshold value obtained by adding the target soil volume to the mass α. By setting a threshold value, the timing for determining that the load mass reduction has finished can be clarified, and the controller 50 can start the tilting movement of the bucket 14 at the appropriate timing.

[0177] The threshold value for determining that the load mass has been reduced may be any value determined from the target soil volume. The threshold value may be a value different from the target soil volume. The threshold value does not necessarily have to be a constant value. If the threshold value is the target soil volume plus the mass α, the value α may be increased if the rate of reduction of the load mass is high, so that the bucket 14 starts to move in the tilt direction earlier. This makes it possible to prevent the bucket 14 from dumping too much of the load.

[0178] In the embodiment of auto tip-off, an example has been described in which, after the processing of Step 1 is performed, one or both of the processing of Step 2 and Step 3 is performed. The processing of Step 1 may be omitted. Simultaneously with the start of auto tip-off, control of Step 2 may be performed to determine the speed of the bucket 14 based on the magnitude of the difference between the current load mass and the target load mass.

[0179] The work machine does not have to be operated by an operator in the cab 5. The work machine may be remotely controlled by radio from a location away from the work site. By having the controller 50 mounted on the work machine automatically perform tip-off, the effect of response delays that can occur when manually operating from a remote location can be eliminated, enabling highly accurate tip-off.

[0180] <Additional Notes> The above description includes the following additional features.

[0181] (Appendix 1) The car body and a work machine attached to the vehicle body and having a bucket at its tip; a controller that commands the operation of the work machine, after an excavation operation of excavating an excavation target with the bucket, the controller moves the bucket in a dump direction toward a specific bucket attitude determined by a relationship between a load mass, which is the mass of the excavation target in the bucket, and an attitude of the bucket, and a target load mass, which is a target value of the load mass; The specific bucket attitude is an attitude that is tilted back more than the attitude of the bucket when the excavation target of the target load mass is accommodated in the bucket.

[0182] (Appendix 2) 2. The work machine according to claim 1, wherein the controller moves the bucket in the dump direction when the load mass after the excavation operation is greater than the target load mass.

[0183] (Appendix 3) 3. The work machine of claim 1 or 2, wherein the controller moves the bucket at a constant speed toward the specific bucket attitude.

[0184] (Appendix 4) 4. The work machine of any one of Supplementary Note 1 to Supplementary Note 3, wherein the controller determines a velocity of the bucket toward the specific bucket attitude based on the target load mass.

[0185] (Appendix 5) 5. The work machine according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the controller continues to move the bucket in the dump direction after the bucket reaches the specific bucket attitude.

[0186] (Appendix 6) The work machine of claim 5, wherein the controller causes a velocity of the bucket after the specific bucket attitude is reached to be slower than a velocity of the bucket before the specific bucket attitude is reached.

[0187] (Appendix 7) The work machine according to claim 5 or 6, wherein the controller determines a velocity of the bucket after the specific bucket attitude is reached based on the current load mass and the target load mass.

[0188] (Appendix 8) The work machine according to claim 7, wherein the controller determines the velocity of the bucket after the specific bucket attitude is reached based on the magnitude of a difference between the current load mass and the target load mass.

[0189] (Appendix 9) The work machine of any one of Supplementary notes 5 to 8, wherein the controller continues to move the bucket in the dump direction after the bucket reaches a second specific bucket attitude.

[0190] (Appendix 10) 10. The work machine of claim 9, wherein the controller causes a velocity of the bucket after the second specific bucket attitude is reached to be slower than a velocity of the bucket before the second specific bucket attitude is reached.

[0191] (Appendix 11) the controller, when the bucket reaches a second specific bucket position before reaching the specific bucket position, continues to move the bucket in the dump direction and reduces a velocity of the bucket after reaching the second specific bucket position compared to a velocity of the bucket before reaching the second specific bucket position.

[0192] (Appendix 12) 12. The work machine of any one of Supplementary notes 9 to 11, wherein the controller operates the bucket such that, after the second specific bucket attitude is reached, a rate of decrease in the load mass becomes constant.

[0193] (Appendix 13) the work machine has the bucket and a boom attached to the vehicle body, 13. The work machine of any one of claims 1 to 12, wherein the controller raises the boom while moving the bucket in the dump direction.

[0194] The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined not by the above description but by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0195] 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 An auto tip-off start determination unit, 512 an auto tip-off control unit, and 513 an auto tip-off end determination unit.

Claims

1. The car body and a work machine attached to the vehicle body and having a bucket at its tip; a controller that commands the operation of the work machine, after an excavation operation of excavating an excavation target with the bucket, the controller moves the bucket in a dump direction toward a specific bucket attitude determined by a relationship between a load mass, which is the mass of the excavation target in the bucket, and an attitude of the bucket, and a target load mass, which is a target value of the load mass; The specific bucket attitude is an attitude that is tilted back more than the attitude of the bucket when the excavation target of the target load mass is accommodated in the bucket.

2. The work machine according to claim 1 , wherein the controller operates the bucket in the dump direction when the load mass after the excavation operation is greater than the target load mass.

3. The work machine according to claim 1 or 2, wherein the controller moves the bucket at a constant speed toward the specific bucket attitude.

4. The work machine according to claim 1 or 2, wherein the controller determines the speed of the bucket toward the specific bucket attitude based on the target load mass.

5. The work machine according to claim 1 , wherein the controller continues to move the bucket in the dump direction after the bucket reaches the specific bucket attitude.

6. The work machine according to claim 5 , wherein the controller reduces the velocity of the bucket after the specific bucket attitude is reached to less than the velocity of the bucket before the specific bucket attitude is reached.

7. The work machine according to claim 5 , wherein the controller determines the velocity of the bucket after the specific bucket attitude is reached based on the current load mass and the target load mass.

8. The work machine according to claim 7 , wherein the controller determines the velocity of the bucket after the specific bucket attitude is reached based on the magnitude of the difference between the current load mass and the target load mass.

9. The work machine according to claim 5 , wherein the controller continues to move the bucket in the dump direction after the bucket reaches a second specific bucket attitude.

10. The work machine according to claim 9 , wherein the controller reduces the velocity of the bucket after the second specific bucket attitude is reached to less than the velocity of the bucket before the second specific bucket attitude is reached.

11. 2. The work machine according to claim 1, wherein, when the bucket reaches a second specific bucket attitude before reaching the specific bucket attitude, the controller continues to move the bucket in the dump direction and makes the velocity of the bucket after reaching the second specific bucket attitude slower than the velocity of the bucket before reaching the second specific bucket attitude.

12. 12. The work machine according to claim 10 or 11, wherein the controller operates the bucket such that, after the second specific bucket attitude is reached, the rate at which the load mass decreases becomes constant.

13. the work machine has the bucket and a boom attached to the vehicle body, 12. A work machine according to claim 1, claim 5, claim 9 or claim 11, wherein the controller raises the boom while moving the bucket in the dumping direction.

14. a work machine including a vehicle body and a work implement attached to the vehicle body and having a bucket at its tip; a controller that commands the operation of the work machine, after an excavation operation of excavating an excavation target with the bucket, the controller moves the bucket in a dump direction toward a specific bucket attitude determined by a relationship between a load mass, which is the mass of the excavation target in the bucket, and an attitude of the bucket, and a target load mass, which is a target value of the load mass; A system including a work machine, wherein the specific bucket attitude is an attitude that is tilted back more than the attitude of the bucket when the excavation target of the target load mass is accommodated in the bucket.

15. performing an excavation operation of excavating an excavation target with a bucket at the tip of the work implement; determining a specific bucket attitude based on a relationship between a load mass, which is the mass of the excavation target in the bucket, and the attitude of the bucket, and a target load mass, which is a target value of the load mass; the specific bucket posture is a posture that is tilted back more than the posture of the bucket when the excavation target having the target load mass is accommodated in the bucket, The method for controlling a work machine further comprises, after the excavation operation, moving the bucket in a dump direction toward the specific bucket attitude.

Images