Wheel loader

Abstract

The present invention provides a wheel loader capable of fully loading a bucket with cargo regardless of the size, nature, and action content before the start of excavation of the work object. In a wheel loader (1) having an excavation assisting controller (5) that automatically controls a work device (2), the excavation assisting controller (5) continues to output an instruction signal related to a raising action to an electromagnetic control valve (481) for a lift arm and outputs an instruction signal related to a tilting action to an electromagnetic control valve (482) for a bucket until the bucket (23) is in a predetermined posture, in the case where the bucket (23) is in a posture that is inclined forward of the predetermined posture, and outputs an instruction signal related to a full tilting action to the electromagnetic control valve (482) for the bucket in the case where the posture of the bucket (23) reaches the predetermined posture.

Description

Technical Field

[0001] This invention relates to a wheel loader equipped with an automatic excavation control system. Background Technology

[0002] In recent years, to improve work efficiency, wheel loaders have emerged that use controllers to control the operation of the working device for excavation. The controller determines that the wheel loader is in the state of starting excavation and, instead of the operator operating the operating device, outputs command signals related to the lifting operation of the boom and the erection operation of the bucket (also known as tilting or unloading operation) to the drive circuit of the working device, thereby causing the working device to move.

[0003] For example, Patent Document 1 discloses a wheel loader in which the controller generates command signals based on the tilting speed of the bucket, the driving amount of the bucket cylinder, and a preset time, and starts and stops the tilting action of the bucket according to the command signals generated in the controller. In this wheel loader, digging can be performed with a pre-planned trajectory of bucket movement.

[0004] Furthermore, in the wheel loader described in Patent Document 2, the controller automatically initiates the bucket tilting action (automatic tilting action) based on the bottom pressure of the boom cylinder and the vehicle speed, and terminates the automatic tilting action based on the amount of rise of the boom cylinder from the bottom pressure at the time the bucket begins to tilt. Therefore, this wheel loader can control the working device according to the magnitude of the traction force.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: U.S. Patent Application Publication No. 2006 / 0245896

[0008] Patent Document 2: International Publication No. 2015 / 004809 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] The angle of repose between the slope and the horizontal plane varies depending on the composition of the soil pile being excavated by a wheel loader, such as sand or minerals. However, in the case of the wheel loader described in Patent Document 1, the bucket moves along a pre-planned trajectory from the start to the end of the excavation operation. Therefore, it may not be possible to scoop a sufficient amount of cargo into the bucket based on the size of the angle of repose. For example, when the angle of repose is large, and the bucket is at a horizontal position or slightly tilted forward (towards the vehicle body), the reaction force from the soil pile (sand, minerals, etc.) during the excavation operation is not too large. This allows the working device to be lifted upwards while the vehicle body moves forward, thus enabling the bucket to be inserted deep relative to the soil pile and a large amount of cargo to be scooped into the bucket. On the other hand, when the angle of repose is small, and the bucket is at a horizontal position or slightly tilted forward (away from the vehicle body), the reaction force from the soil pile (sand, minerals, etc.) during excavation is not excessive. This allows the workpiece to be lifted upwards while the vehicle body moves forward, enabling the bucket to be inserted deep relative to the soil pile and a large amount of cargo to be loaded into the bucket. Furthermore, even when excavating soil piles of the same size angle of repose, the trajectory of the workpiece differs depending on its initial posture. Therefore, in such cases, it may sometimes be impossible to scoop a sufficient amount of cargo into the bucket.

[0011] On the other hand, in the wheel loader described in Patent Document 2, the controller determines the start and end of the digging operation based on the bottom pressure of the lifting arm cylinder, and the movement trajectory of the bucket changes according to the size of the angle of repose of the soil pile. Therefore, unlike the wheel loader described in Patent Document 1, even with soil piles of different sizes relative to the angle of repose, a sufficient amount of cargo can be shoveled into the bucket.

[0012] When a wheel loader scoops cargo into its bucket, it utilizes the reaction force from the soil pile relative to the forward driving force to move the cargo towards the inside of the bucket. Therefore, it is preferable that the bucket is not tilted significantly backward in the stage before the excavation operation ends. However, in the case of the wheel loader described in Patent Document 2, the controller determines the end of the excavation operation based on the bottom pressure of the boom cylinder. Therefore, for example, depending on the vehicle speed before excavation began and the hardness of the soil pile, in the stage before the final stage of the excavation operation, the bottom pressure of the boom cylinder rises to a value close to the end pressure, and sometimes the bucket changes to a significantly tilted backward posture (close to a fully tilted posture). In this case, the cargo cannot be moved sufficiently to the inside of the bucket by the bucket action in the final stage of the excavation operation, and the cargo is loaded on the claw tip side of the bucket (near the opening), and the cargo may spill out of the bucket during the handling operation after the excavation operation.

[0013] Therefore, the purpose of this invention is to provide a wheel loader that can fully load goods into the bucket regardless of the size, shape, or pre-excavation actions of the work object.

[0014] Methods for solving problems

[0015] To achieve the above objectives, the present invention provides a wheel loader comprising: a lifting arm mounted at the front of a vehicle body and rotating vertically relative to the vehicle body; a bucket mounted at the front end of the lifting arm and digging for work by tilting backward toward the vehicle body through an upward rotation relative to the lifting arm; a lifting arm cylinder driving the lifting arm; a bucket cylinder driving the bucket; a lifting arm solenoid control valve controlling the lifting arm cylinder; a bucket solenoid control valve controlling the bucket cylinder; and a controller controlling the lifting arm solenoid control valve and the bucket solenoid control valve, respectively. The wheel loader is characterized in that it includes: a pressure sensor detecting the bottom pressure of the lifting arm cylinder; and a bucket posture sensor detecting the posture of the bucket. The controller, upon detection by the pressure sensor... When the bottom pressure reaches a first pressure threshold equivalent to the bottom pressure of the lifting arm in the state where the lifting arm is not in motion and the bucket is in contact with the work object, a command signal related to the lifting arm's rising action is output to the lifting arm solenoid control valve. When the bucket's posture detected by the bucket posture sensor is a posture that is tilted forward compared to a predetermined posture, a command signal related to the lifting arm's rising action is continued to be output to the lifting arm solenoid control valve, and a command signal related to the bucket's tilting action is output to the bucket solenoid control valve until the bucket reaches the predetermined posture. When the bucket's posture detected by the bucket posture sensor reaches the predetermined posture, a command signal related to the bucket's full tilting action is output to the bucket solenoid control valve.

[0016] Invention Effects

[0017] According to the present invention, regardless of the size, shape, or pre-excavation actions of the work object, the bucket can be fully loaded with goods. Other issues, structures, and effects beyond those described above will become clear through the following description of the embodiments. Attached Figure Description

[0018] Figure 1 This is an external side view showing a structural example of a wheel loader according to an embodiment of the present invention.

[0019] Figure 2 Viewed from the left front Figure 1 The image shown is a 3D view of a wheel loader.

[0020] Figure 3A This diagram illustrates the situation where the bucket of a wheel loader enters a pile of soil during excavation operations.

[0021] Figure 3B This diagram illustrates the tilting motion of the bucket during excavation operations on a wheel loader.

[0022] Figure 3C This diagram illustrates the raising of the boom during excavation operations using a wheel loader.

[0023] Figure 4 This is a system structure diagram illustrating an example of the drive unit of a wheel loader.

[0024] Figure 5 This is a function block diagram representing the functions of the excavation auxiliary controller.

[0025] Figure 6 It is a graph showing the change in acceleration of the wheel loader over time at the start of the excavation operation.

[0026] Figure 7 It is a flowchart representing the process executed by the excavation-aid controller.

[0027] Figure 8 It means Figure 7 The subsequent process X in the flowchart shown.

[0028] Figure 9 It means Figure 8 The subsequent process Y in the flowchart shown.

[0029] Figure 10 This is a schematic representation of the excavation-aided controller performing operations. Figures 7-9 A diagram showing the initial posture of the working device under the processing conditions.

[0030] Figure 11 It is a schematic representation in Figure 8 A diagram showing the posture of the working device when entering the "Yes" state in step S616.

[0031] Figure 12 It is a schematic representation in Figure 8 A diagram showing the posture of the working device when entering the "Yes" state in step S620.

[0032] Figure 13 It is a schematic representation in Figure 8 A diagram showing the posture of the working device when entering the "Yes" state in step S625.

[0033] Figure 14It is a schematic representation in Figure 9 A diagram showing the posture of the working device when entering the "Yes" state in step S629.

[0034] Figure 15 It is a schematic representation in Figure 9 A diagram showing the posture of the working device when entering the "Yes" state in step S633.

[0035] Figure 16 It is a schematic representation in Figure 9 A diagram showing the posture of the working device when entering the "Yes" state in step S637. Detailed Implementation

[0036] (Overall structure of wheel loader 1)

[0037] First, refer to Figure 1 and Figure 2 The overall structure of the wheel loader 1 according to an embodiment of the present invention will be described.

[0038] Figure 1 This is an external side view showing a structural example of a wheel loader 1 according to an embodiment of the present invention. Figure 2 Viewed from the left front Figure 1 The diagram shows a perspective view of the wheel loader 1.

[0039] The wheel loader 1 is an articulated work vehicle that turns by bending its body near the center. The front frame 1A, which forms the front of the vehicle body, and the rear frame 1B, which forms the rear of the vehicle body, are connected by a central joint 10, allowing free rotation in the left-right direction. The front frame 1A bends relative to the rear frame 1B in the left-right direction. Furthermore, in the following description, the direction to the left of the vehicle body relative to the forward direction is designated as the "left direction," and the direction to the right of the forward direction is designated as the "right direction."

[0040] The vehicle body has four wheels 11. Two wheels 11 serve as front wheels 11A and are located on the left and right sides of the front frame 1A. The remaining two wheels 11 serve as rear wheels 11B and are located on the left and right sides of the rear frame 1B. Figure 1 The text only indicates the front wheel 11A and rear wheel 11B located on the left side of the four wheels 11. Additionally, in... Figure 2 The text only indicates the left and right front wheels 11A and the left rear wheel 11B out of the four wheels 11. Furthermore, there is no particular limitation on the specific number of wheels 11 installed on the vehicle body.

[0041] A hydraulically driven operating device 2 is installed at the front of the front frame 1A. This hydraulically driven operating device 2 is used for loading and unloading operations such as digging sand, soil, and minerals and loading them into dump trucks, hoppers, etc.

[0042] The rear frame 1B includes a cab 12 for the operator, a machine room 13 that houses the various equipment required to drive the wheel loader 1, and a counterweight 14 for maintaining balance with the working device 2 to prevent the vehicle from tipping over. In the rear frame 1B, the cab 12 is located at the front, the counterweight 14 is located at the rear, and the machine room 13 is located between the cab 12 and the counterweight 14.

[0043] The working device 2 includes: a lifting arm 21, which is mounted on the front frame 1A in a manner that allows it to rotate in the vertical direction; and two lifting arm cylinders 22L and 22R (see reference) that function as hydraulic cylinders. Figure 4 These components drive the lifting arm 21; the bucket 23 is mounted on the front end of the lifting arm 21 in a manner that allows it to rotate in the vertical direction; the bucket cylinder 24, which is a hydraulic cylinder, drives the bucket 23; and the double-arm crank 25 is rotatably connected to the lifting arm 21, forming a linkage mechanism between the bucket 23 and the bucket cylinder 24.

[0044] Furthermore, the two lifting arm cylinders 22L and 22R are arranged at predetermined intervals in the left-right direction of the vehicle body, but... Figure 1 In the middle, it is positioned where it is obscured by the front wheel 11A on the left side, and therefore is not shown in the diagram. Figure 2 The text only indicates the 22L lifting arm cylinder on the left side.

[0045] The lifting arm 21 rotates upward relative to the front frame 1A by extending the rods 220 of the two lifting arm cylinders 22L and 22R, and rotates downward relative to the front frame 1A by retracting the rods 220 of the two lifting arm cylinders 22L and 22R. A lifting arm angle sensor 31 is installed at the base of the lifting arm 21 (the mounting part with the front frame 1A). This lifting arm angle sensor 31 detects the angle α between the ground contact point (the ground contacted by the four wheels 11) of the wheel loader 1 and the lifting arm 21. Furthermore, the lifting arm angle sensor 31 is also a lifting arm posture sensor for detecting the posture of the lifting arm 21.

[0046] The bucket 23 extends via the rod 240 of the bucket cylinder 24, causing it to rotate upward relative to the lifting arm 21 and tilt backward toward the front frame 1A (tilting action). Conversely, the bucket 23 retracts via the rod 240 of the bucket cylinder 24, causing it to rotate downward relative to the lifting arm 21 (unloading action). Thus, the bucket 23 can scoop up and discharge work objects such as sand and minerals (soil discharge).

[0047] The angle β between the ground contact point of the wheel loader 1 and the bottom surface of the bucket 23 can be calculated based on the boom angle α and the tilt angle γ of the boom crank 25 relative to the front frame 1A. Therefore, the boom angle sensor 31, which detects the boom angle α, and the boom crank angle sensor 32, which is mounted on the boom crank 25 and detects the boom crank angle γ, are equivalent to bucket posture sensors that detect the posture of the bucket 23. Furthermore, the bucket posture sensor does not necessarily need to be an angle sensor; for example, it could be a position sensor that detects the position of the bucket 23.

[0048] The bucket 23 can be replaced with various accessories such as scrapers. In addition to loading and unloading operations using the bucket 23, the wheel loader 1 can also perform various operations such as snow removal, soil compaction (bulldozing).

[0049] (Regarding excavation operations)

[0050] Next, refer to Figures 3A-3C The excavation operation of wheel loader 1 is described.

[0051] Figures 3A-3C This is an explanatory diagram illustrating the excavation operation of wheel loader 1. Figure 3A This indicates the situation where bucket 23 enters the soil pile Q. Figure 3B This indicates the situation where the bucket 23 tilts. Figure 3C This indicates the situation where the lifting arm 21 is raised.

[0052] During the excavation operation, firstly, the wheel loader 1 moves towards the soil pile Q, which is the object of the operation, at full acceleration, so that the bucket 23 enters the soil pile Q. Figure 3A (As shown in the diagram). Next, the operator raises the boom 21 and tilts the bucket 23, thereby scooping up the sand, minerals, etc. that make up the pile Q by the wheel loader 1. Figure 3B (As shown in the diagram). Then, the operator continues the lifting operation of the lifting arm 21, thereby further lifting the bucket 23, which is loaded with the scooped-up goods, upwards. Figure 3C (The state shown).

[0053] In addition, when shoveling up goods such as sand and minerals and loading them into the bucket 23 ( Figure 3B As shown in the diagram, depending on the properties of the constituent elements constituting the mound Q, sometimes a single tilting operation of the bucket 23 by the operator is insufficient to load the cargo into the inner side of the bucket 23. In such cases, the operator may need to perform the tilting operation of the bucket 23 multiple times.

[0054] In the case of multiple tilting operations of the bucket 23, in the initial stage (e.g., the first and second times), the cargo is moved inwards from the pile Q by the reaction force from the forward driving force output by the wheel loader 1. Therefore, it is preferable that the posture of the bucket 23 does not tilt significantly backwards towards the cab 12. On the other hand, in the final tilting operation of the bucket 23, it is preferable to tilt the bucket 23 significantly backwards towards the cab 12, thereby imparting a rearward inertia to the cargo and causing it to move inwards from the bucket 23.

[0055] In this wheel loader 1, in addition to manually operating the working device 2 to perform digging operations, it is also possible to use a digging assistance controller 5 (described later) for digging assistance. Figure 4 and Figure 5 The excavation operation is carried out by the automatic control of the working device 2.

[0056] (Drive unit 400 of wheel loader 1)

[0057] Next, refer to Figure 4 The drive unit 400 of the wheel loader 1 will be described.

[0058] Figure 4 This is a system structure diagram representing a structural example of the drive unit 400 of a wheel loader 1.

[0059] The drive unit 400 of the wheel loader 1 is configured by including the following parts: a travel drive unit 401 for moving the vehicle body, a braking drive unit 402 for applying braking force to the moving vehicle body, a steering drive unit 403 for steering, and a work drive unit 404 for operating the work device 2.

[0060] The engine 40, which serves as the drive source for the driving drive unit 401, braking drive unit 402, steering drive unit 403, and work drive unit 404, has its speed controlled by the engine controller 40A. The engine controller 40A outputs a control signal to the engine 40 related to the target engine speed based on the amount of pressure applied to the accelerator pedal 121. The amount of pressure applied to the accelerator pedal 121 is detected by an accelerator pedal pressure sensor 33 installed on the accelerator pedal 121.

[0061] In this embodiment, the driving drive unit 401 is a torque converter type, having a torque converter 41 connected to the output shaft of the engine 40 to amplify the torque transmitted from the engine 40, and a transmission 42 connected to the output shaft of the torque converter 41. The output shaft of the torque converter 41 is connected to the drive shaft 15 via the transmission 42, and the driving force output from the engine 40 is transmitted to the four wheels 11 via the torque converter 41, the transmission 42, and the drive shaft 15.

[0062] The torque converter 41 is configured such that the greater the input speed (the speed of the output shaft of the engine 40) relative to the output speed, the greater the driving force transmitted to the transmission 42. Therefore, if the accelerator pedal 121 is pressed more, increasing the engine speed of the engine 40, the driving force output by the torque converter 41 increases. The torque converter 41 is equipped with a torque sensor 34 for detecting the output torque Tr of the torque converter 41 and a speed sensor 35 for detecting the output speed R of the torque converter.

[0063] According to the control signal output from the transmission controller 42A, the transmission 42 can either disconnect the output shaft of the torque converter 41 from the drive shaft 15 to reduce the driving force of the four wheels 11, or reverse the rotation direction of the drive shaft 15 to switch the direction of the driving force of the four wheels 11. The transmission controller 42A receives a switching signal output from the forward / reverse switching switch 122 and the brake pedal 123 pedal pressure SB detected by the brake pedal pressure sensor 36. The forward / reverse switching switch 122 serves as a forward / reverse switching device for switching the vehicle's forward and reverse directions.

[0064] For example, when the switching signal output from the forward / reverse switch 122 is a stop-related neutral signal, and the braking amount detected by the brake pedal pressure sensor 36 is above a predetermined braking amount, the transmission controller 42A outputs a control signal to the transmission 42 to disconnect the connection between the output shaft of the torque converter 41 and the drive shaft 15.

[0065] A vehicle speed sensor 37 is provided on the output side of the transmission 42 to detect vehicle speed by detecting the rotational speed of the drive shaft 15. Furthermore, this vehicle speed sensor 37 can also detect acceleration based on vehicle speed. In other words, the vehicle speed sensor 37 is an acceleration sensor that detects the acceleration of the wheel loader 1.

[0066] The brake drive unit 402 includes: a brake pump 43 connected to the output shaft of the engine 40, a reservoir 44 for accumulating pressurized oil injected from the brake pump 43, and a brake control circuit 45 for controlling the braking force of the four wheels 11. In the brake control circuit 45, the control pressure for controlling the braking force of the four wheels 11 is adjusted according to the amount of braking of the brake pedal 123 detected by the brake pedal depressor sensor 36.

[0067] The steering drive unit 403 includes: left and right steering cylinders 10L and 10R that turn left and right by extending and retracting the lever 100; a main pump 46 that supplies pressurized oil to the left and right steering cylinders 10L and 10R by connecting to the output shaft of the engine 40; and a steering control circuit 47 that controls the left and right steering cylinders 10L and 10R according to the amount and direction of operation of the steering wheel 126.

[0068] The steering control circuit 47 is configured by including: a steering direction control valve that controls the flow (direction and flow rate) of pressurized oil injected from the master pump 46 and supplied to the left and right steering cylinders 10L and 10R respectively; and a steering solenoid control valve that controls the steering direction control valve according to the steering signal output from the steering wheel 126. The steering solenoid control valve controls the left and right steering cylinders 10L and 10R by controlling the steering direction control valve.

[0069] For example, when the operator turns the steering wheel 126 to the right, the steering control circuit 47 connects the injection side of the master pump 46 to the bottom chamber of the left steering cylinder 10L and the injection side of the master pump 46 to the rod chamber of the right steering cylinder 10R according to the steering signal of the right turn output from the steering wheel 126.

[0070] As a result, the pressurized oil injected from the main pump 46 flows into the bottom chamber of the left steering cylinder 10L and the rod chamber of the right steering cylinder 10R respectively. Therefore, the rod 100 of the left steering cylinder 10L extends and the rod 100 of the right steering cylinder 10R retracts, causing the wheel loader 1 to turn right.

[0071] On the other hand, when the operator turns the steering wheel 126 to the left, the steering control circuit 47 connects the injection side of the master pump 46 to the rod chamber of the left steering cylinder 10L and the injection side of the master pump 46 to the bottom chamber of the right steering cylinder 10R according to the left rotation steering signal output from the steering wheel 126.

[0072] As a result, the pressurized oil injected from the main pump 46 flows into the rod chamber of the left steering cylinder 10L and the bottom chamber of the right steering cylinder 10R respectively. Therefore, the rod 100 of the left steering cylinder 10L retracts and the rod 100 of the right steering cylinder 10R extends, causing the wheel loader 1 to turn left.

[0073] The operating drive unit 404 includes: two boom cylinders 22L and 22R; a bucket cylinder 24; a main pump 46 that supplies pressurized oil to the two boom cylinders 22L and 22R and the bucket cylinder 24; and an operating device control circuit 48 that controls the flow of pressurized oil supplied from the main pump 46 to the two boom cylinders 22L and 22R and the bucket cylinder 24 according to the amount and direction of operation of the boom operating lever 124 and the bucket operating lever 125.

[0074] The higher the rotational speed of the output shaft of engine 40, the greater the flow rate of pressurized oil injected from the main pump 46. Therefore, by increasing the amount of pressure applied to the accelerator pedal 121, the rotational speed of the output shaft of engine 40 is increased, resulting in faster extension and retraction speeds of the rods 220 of the two lifting arm cylinders 22L and 22R, and the rod 240 of the bucket cylinder 24. Furthermore, in Figure 4In this embodiment, the main pump 46 is shared in the steering drive unit 403 and the work drive unit 404, but it is not necessary to use the same hydraulic pump. Alternatively, each of the steering drive unit 403 and the work drive unit 404 may have a separate hydraulic pump.

[0075] The operating device control circuit 48 is configured by including the following components: a directional control valve for the boom, which controls the flow of pressurized oil injected from the main pump 46 and supplied to the two boom cylinders 22L and 22R respectively; and a solenoid control valve 481 for the boom (see reference). Figure 5 The boom directional control valve controls the boom based on the boom operation signal output from the boom operating lever 124; the bucket directional control valve controls the flow of pressurized oil injected from the main pump 46 and supplied to the bucket cylinder 24; and the bucket solenoid control valve 482 (see reference). Figure 5 It controls the bucket directional control valve based on the bucket operation signal output from the bucket operating lever 125.

[0076] The boom solenoid control valve 481 controls the two boom cylinders 22L and 22R by controlling the boom directional control valve. Similarly, the bucket solenoid control valve 482 controls the bucket cylinder 24 by controlling the bucket directional control valve.

[0077] For example, when the operator operates the boom operating lever 124 to raise the boom 21, the working device control circuit 48 connects the main pump 46 to the bottom chambers 22B of the two boom cylinders 22L and 22R according to the boom lifting operation signal output from the boom operating lever 124.

[0078] As a result, the pressurized oil injected from the main pump 46 flows into the bottom chamber 22B of the two lifting arm cylinders 22L and 22R, thus extending each rod 220 and causing the lifting arm 21 to move upward.

[0079] Additionally, for example, when the operator operates the bucket operating lever 125 to tilt the bucket 23, the working device control circuit 48 connects the main pump 46 to the bottom chamber 24B of the bucket cylinder 24 according to the tilt operation signal output from the bucket operating lever 125.

[0080] As a result, the pressurized oil injected from the main pump 46 flows into the bottom chamber 24B of the bucket cylinder 24, causing the rod 240 to extend and the bucket 23 to tilt (erect).

[0081] One of the two lifting boom cylinders 22L and 22R, the lifting boom cylinder 22L is equipped with a lifting boom rod pressure sensor 38A for detecting the internal pressure of the rod chamber 22A (rod pressure PLr) and a lifting boom bottom pressure sensor 38B for detecting the internal pressure of the bottom chamber 22B (bottom pressure PLb). Furthermore, in... Figure 4In the middle, the lifting arm rod pressure sensor 38A and the lifting arm bottom pressure sensor 38B are installed on the left lifting arm cylinder 22L, but they can also be installed on the right lifting arm cylinder 22R.

[0082] Similarly, a bucket rod pressure sensor 39A for detecting the internal pressure of the rod chamber 24A (rod pressure PBr) and a bucket bottom pressure sensor 39B for detecting the internal pressure of the bottom chamber 24B (bottom pressure PBb) are respectively installed in the bucket cylinder 24.

[0083] In the wheel loader 1, the working device control circuit 48 (solenoid control valve 481 for the boom and solenoid control valve 482 for the bucket) is controlled by the excavation assistance controller 5. Therefore, even without operator input of the boom control lever 124 and bucket control lever 125, the working device 2 can automatically operate to perform excavation work. The excavation assistance control system of the working device 2 based on the excavation assistance controller 5 is activated by the operator by turning on the excavation assistance start switch 49 located in the cab 12.

[0084] (Structure of the excavation auxiliary controller 5)

[0085] Next, refer to Figure 5 and Figure 6 The structure of the excavation assistance controller 5 will be described. Furthermore, in the following description, the excavation assistance controller 5 will be simply referred to as "controller 5".

[0086] Figure 5 This is a function block diagram representing the functions of controller 5.

[0087] The controller 5 is configured with a CPU, RAM, ROM, HDD, input I / F, and output I / F interconnected via a bus. Furthermore, various operating devices such as the excavation assist start switch 49 and the forward / reverse switch 122, as well as various sensors such as the boom angle sensor 31, boom crank angle sensor 32, accelerator pedal pressure sensor 33, torque sensor 34, speed sensor 35, brake pedal pressure sensor 36, vehicle speed sensor 37, boom rod pressure sensor 38A, boom bottom pressure sensor 38B, bucket rod pressure sensor 39A, and bucket bottom pressure sensor 39B are connected to the input I / F. The boom solenoid control valve 481 and the bucket solenoid control valve 482 (operating device control circuit 48) are connected to the output I / F.

[0088] In this hardware structure, the CPU reads the control program (software) stored in a recording medium such as ROM, HDD or optical disc and expands it in RAM. By executing the expanded control program, the control program and hardware cooperate to realize the function of controller 5.

[0089] Furthermore, in this embodiment, the structure of the controller 5 is described by a combination of software and hardware, but it is not limited to this. It can also be constructed by using an integrated circuit that implements the function of the control program executed on the wheel loader 1 side.

[0090] The controller 5 includes: a data acquisition unit 51, a determination unit 52, an instruction signal output unit 53, a processing stage counting unit 54, and a storage unit 55.

[0091] The data acquisition unit 51 acquires data related to the start signal output from the digging assist start switch 49, the lever pressure PLr detected by the boom lever pressure sensor 38A, the bottom pressure PLb detected by the boom bottom pressure sensor 38B, the lever pressure PBr detected by the bucket lever pressure sensor 39A, the bottom pressure PBb detected by the bucket bottom pressure sensor 39B, the switching signal output from the forward / reverse switch 122, the vehicle speed V detected by the vehicle speed sensor 37, the boom angle α detected by the boom angle sensor 31, the double boom crank angle γ detected by the double boom crank angle sensor 32, the accelerator pedal pedal amount SA detected by the accelerator pedal pedal amount sensor 33, the brake pedal pedal amount SB detected by the brake pedal pedal amount sensor 36, the output torque Tr of the torque converter 41 detected by the torque sensor 34, and the output speed R of the torque converter 41 detected by the speed sensor 35.

[0092] The determination unit 52 includes: a start determination unit 521, a digging preparation determination unit 522, a stop request determination unit 523, a digging start determination unit 524, a travel direction determination unit 525, a bucket posture determination unit 526, a boom posture determination unit 527, and a deceleration determination unit 528.

[0093] The start-up determination unit 521 determines whether the excavation auxiliary control system has been started. Specifically, if the start-up determination unit 521 obtains an activation signal from the excavation auxiliary start switch 49 in the data acquisition unit 51, it determines that the excavation auxiliary control system has been started.

[0094] The excavation preparation determination unit 522 determines whether the excavation preparation conditions are met. Here, "excavation preparation conditions" means that the working device 2 is in the excavation posture described later, the operator intends to carry out excavation work, and the bucket 23 is empty.

[0095] Specifically, the excavation preparation determination unit 522 determines that the working device 2 is in an excavation posture when the bucket angle β calculated based on the boom angle α and the double boom crank angle γ obtained in the data acquisition unit 51 is within a predetermined angle threshold βth (0 < β ≤ βth) of the ground contact surface of the wheel loader 1. Furthermore, the "predetermined angle threshold βth" is, for example, 10°, set to the angle at which the bucket 23 can enter the soil pile Q. In addition, the range of the bucket angle β in the excavation posture is set to a range greater than 0, but it is not limited to this; it can be appropriately set to a range corresponding to the angle of repose of the soil pile, for example, it can also be set to a range greater than the negative angle at which the unloading action is performed below the ground contact surface of the vehicle body (e.g., -10° < β ≤ βth).

[0096] Furthermore, if the accelerator pedal depress amount SA obtained from the data acquisition unit 51 is above a predetermined depress amount threshold SAth (SA≥SAth), the excavation preparation determination unit 522 determines that the operator intends to perform excavation work. In addition, the "predetermined depress amount threshold SAth" is set to a value equivalent to the minimum accelerator pedal depress amount required for the wheel loader 1 to move.

[0097] Furthermore, if the bottom pressure PLb of the lifting boom cylinders 22L and 22R obtained by the data acquisition unit 51 is less than the predetermined bottom pressure threshold PLbth (PLb < PLbth), the excavation preparation determination unit 522 determines that the bucket 23 is empty. In addition, the "predetermined bottom pressure threshold PLbth" is set to the bottom pressure applied to the lifting boom cylinders 22L and 22R when there is a minimum amount of cargo in the bucket 23.

[0098] The stop request determination unit 523 determines whether a request has been made to stop the excavation assistance control based on the excavation assistance control system. Specifically, the stop request determination unit 523 determines whether there is operation of the brake pedal 123 based on the brake pedal depress amount SB obtained in the data acquisition unit 51. If there is operation of the brake pedal 123, it determines that a request has been made to stop the excavation assistance control.

[0099] The excavation start determination unit 524 determines whether the excavation start condition is met, i.e., whether the bucket 23 is in contact with the soil pile Q. Here, the "excavation start condition" refers to the pressure PL applied to the two lifting boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 rising, the vehicle speed V being the speed during excavation, and the wheel loader 1 being subjected to force from the soil pile Q.

[0100] Specifically, if the total value P (=PL+PB) of the pressure PL applied to the two lifting boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 is greater than a predetermined first pressure threshold Pth (P>Pth), the excavation start determination unit 524 determines that the pressure PL applied to the two lifting boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 have increased.

[0101] Furthermore, the "first pressure threshold Pth" is set to a value equivalent to the sum of the pressure PL applied to the two boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 when the working device 2 is not activated and is not subjected to external force due to contact or other reasons.

[0102] The excavation start determination unit 524 can also obtain a force equivalent to the pressure PL applied to the two lifting boom cylinders 22L and 22R and a force equivalent to the pressure PB applied to the bucket cylinder 24. If the total value of the obtained forces is greater than the threshold value of the force equivalent to the first pressure threshold Pth, it is determined that the pressure PL applied to the two lifting boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 have increased.

[0103] Here, the force applied to the two lifting arm cylinders 22L and 22R can be obtained by subtracting the product of the lifting arm cylinder 22L's bottom pressure PLb and the cross-sectional area of ​​the bottom chamber 22B from the product of the lifting arm cylinder 22L's rod pressure PLr and the cross-sectional area of ​​the rod chamber 22A, and then multiplying the calculated subtraction value by 2.

[0104] Similarly, the force applied to the bucket cylinder 24 is obtained by subtracting the product of the rod pressure PBr of the bucket cylinder 24 and the cross-sectional area of ​​the rod chamber 24A from the product of the bottom pressure PBb of the bucket cylinder 24 obtained in the data acquisition unit 51 and the cross-sectional area of ​​the bottom chamber 24B.

[0105] In this embodiment, the rise of the pressure PL applied to the two boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 is used as one of the conditions for starting excavation. However, it is not necessary to use the rise of both the pressure PL applied to the two boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 as conditions. It is sufficient to use the rise of the bottom pressure PLb of the boom cylinders 22L and 22R as a condition. Therefore, the "first pressure threshold Pth" only needs to be set to a value that is at least equivalent to the bottom pressure of the boom cylinders 22L and 22R in the state where the boom 21 is not in motion and the bucket 23 is in contact with the soil pile Q.

[0106] However, by taking the rise of both the pressure PL applied to the two boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 as conditions, compared with taking the rise of the bottom pressure PLb of the boom cylinder 22 as a condition, it is possible to suppress false judgments and improve the accuracy of the excavation start determination.

[0107] In this embodiment, the pressure PL applied to the two boom cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 are the bottom pressures PLb of the boom cylinders 22L and 22R and the bottom pressure PBb of the bucket cylinder 24, which are obtained in the data acquisition unit 51. However, the rod pressure PLr of the boom cylinders 22L and 22R and the rod pressure PBr of the bucket cylinder 24 can also be used. In this case, one of the conditions for starting digging is a "decrease" in the pressures applied to the two boom cylinders 22L and 22R and the pressure applied to the bucket cylinder 24.

[0108] Furthermore, if the vehicle speed V obtained by the data acquisition unit 51 is below a predetermined speed threshold Vth (V≤Vth), the excavation start determination unit 524 determines that the vehicle speed V is the speed during excavation operations. In addition, the "predetermined speed threshold Vth" is, for example, 12 km / h, and is set as a speed frequently used during excavation operations.

[0109] Furthermore, if the force F applied to the vehicle body from the outside is greater than or equal to a predetermined force threshold Fth (F≥Fth) when the vehicle body is not accelerating relative to the output of the engine 40, the excavation start determination unit 524 determines that the wheel loader 1 is subjected to force from the soil pile Q, that is, the bucket 23 is in contact with the soil pile Q. In addition, the "predetermined force threshold Fth" is a value equivalent to the force applied to the vehicle body from the soil pile Q when the bucket 23 is in contact with the soil pile Q in the state where the lifting arm 21 is not in motion.

[0110] Here, the force F is calculated by subtracting the product of the output torque Tr of the torque converter 41 obtained in the data acquisition unit 51 and the output speed R of the torque converter 41 (Tr×R), from the product of the vehicle weight W stored in the storage unit 55 and the acceleration VA calculated based on the vehicle speed V obtained in the data acquisition unit 51 (W×VA).

[0111] The direction of travel determination unit 525 determines the direction of travel (forward, backward, or stopped) of the wheel loader 1 based on the switching signal from the forward / reverse switch 122 obtained in the data acquisition unit 51.

[0112] The bucket posture determination unit 526 determines the posture of the bucket 23 based on the bucket angle β calculated from the boom angle α and boom crank angle γ obtained in the data acquisition unit 51. Furthermore, the bucket posture determination unit 526 may not necessarily need to determine the posture of the bucket 23 based on the bucket angle β; for example, it may determine the posture of the bucket 23 based on the position of the bucket cylinder 24, the output time of the bucket 23's motion, etc.

[0113] Specifically, the bucket posture determination unit 526 determines whether the calculated bucket angle β is greater than or equal to the first angle threshold β1, the second angle threshold β2, and the third angle threshold β3.

[0114] Here, "first angle threshold β1" is the angle at which the load can be easily moved inwards towards the bucket 23 using the vehicle's driving force at the beginning of the excavation operation, for example, set to 10°. Furthermore, when the output of the bucket 23 is greatly affected by factors such as high engine speed of the engine 40, the response of the bucket 23 is prone to delay. Therefore, it is preferable to set the first angle threshold β1 to an angle smaller than 10° (for example, 8°).

[0115] "Second angle threshold β2" refers to the state at the beginning of the excavation operation, where the lifting arm 21 rises and the bucket 23 tilts, resulting in a slightly larger bucket angle β. Subsequent rising movements of the lifting arm 21 and tilting movements of the bucket 23 from this state constitute the final actions in the working device 2. Therefore, these final actions are designed to load the cargo into the inner side of the bucket 23 (giving sufficient inertia to the cargo within the bucket 23), and are set to, for example, 20°. During the tilting movement of the bucket 23 in the final action, the bucket 23 tilts to its limit, reaching its final tilt towards the cab 12 (final posture), i.e., a full tilt state. Therefore, the tilting movement of the bucket 23 in the final action conforms to a full tilt action.

[0116] Furthermore, when the amount of movement and speed of the bucket 23 during the full tilting motion of the bucket 23 are set to relatively large values, sufficient inertia can be imparted to the cargo inside the bucket 23 with a relatively small amount of movement. Therefore, the second angle threshold β2 can be set to a relatively large angle, such as 50°. Alternatively, the second angle threshold β2 can be set in relation to the speed of movement relative to the amount of movement of the bucket 23 up to this point.

[0117] The "third angle threshold β3" is an angle that allows the cargo to be loaded onto the inside of the bucket 23 (giving sufficient inertia to the cargo inside the bucket 23) with only one subsequent tilting action of the bucket 23, and is set to, for example, an angle between 20° and 50°. That is, the "subsequent tilting action of the bucket 23" conforms to a full tilting action. Therefore, the "third angle threshold β3" is preferably set to an angle that sufficiently ensures the amount of action of the full tilting action from this state to the point where the bucket 23 is in a full tilting state. In addition, regarding this third angle threshold β3, there may also be a case similar to the second angle threshold β2, where the second angle threshold β2 is added to the second angle threshold β2, which is envisioned to be in step S633 described later (refer to...). Figure 9 The value is obtained by measuring the change in the bucket angle β during the process.

[0118] If the calculated bucket angle β is greater than or equal to the third angle threshold β3 (β≥β3), the bucket posture determination unit 526 determines that the posture of the bucket 23 is the final posture that can load the cargo onto the inside of the bucket 23 through a subsequent tilting action (full tilting action).

[0119] Here, "first angle threshold β1", "second angle threshold β2" and "third angle threshold β3" are all ways of defining the "predetermined tilting threshold" of the bucket 23.

[0120] The lifting arm posture determination unit 527 determines the rising angle αr of the lifting arm 21 from the reference angle αs (described later) of the lifting arm 21 (refer to...). Figure 10 Whether the lifting arm rise angle (hereinafter referred to as "lifting arm rise angle αr") is greater than or equal to the first rise angle threshold αr1 (e.g., 5°) or greater, or whether the bottom pressure PLb of the lifting arm cylinder 22L obtained in the data acquisition unit 51 is greater than or equal to the predetermined upper limit pressure Prlim.

[0121] In addition, the lifting arm posture determination unit 527 determines whether the lifting arm rising angle αr from the reference angle αs of the lifting arm 21 is greater than or equal to the second rising angle threshold αr2 (e.g., 10°) or whether the bottom pressure PLb of the lifting arm cylinder 22L obtained in the data acquisition unit 51 is greater than or equal to the predetermined upper limit pressure Prlim.

[0122] In addition, the lifting arm posture determination unit 527 determines whether the lifting arm rising angle αr from the reference angle αs of the lifting arm 21 is greater than or equal to the third rising angle threshold αr3 (e.g., 15°) or whether the bottom pressure PLb of the lifting arm cylinder 22L obtained in the data acquisition unit 51 is greater than or equal to the predetermined upper limit pressure Prlim.

[0123] Here, "first rise angle threshold αr1", "second rise angle threshold αr2" and "third rise angle threshold αr3" are all ways of defining the "predetermined rise amount threshold" in the lifting arm 21.

[0124] The "predetermined upper limit pressure Prlim" is equivalent to a second pressure threshold that is larger than the first pressure threshold Pth, and is preferably set to a value slightly smaller than the set overflow pressure, which is the pressure released when the pressure in the hydraulic line in the working device control circuit 48 reaches its limit.

[0125] Furthermore, in this embodiment, the lifting arm posture determination unit 527 uses the rising angle αr (rising amount) of the lifting arm 21 from the reference angle αs (reference posture) to determine the posture (state) of the lifting arm 21, but is not limited to this. For example, the angle between the ground contact surface of the wheel loader 1 and the bottom surface of the front end of the lifting arm 21 (bottom surface of the working device 2) and the vertical height from the ground contact surface of the wheel loader 1 to the front end of the lifting arm 21 (bucket pin) can be used to determine the state of the lifting arm 21 based on the preset posture of the lifting arm 21.

[0126] The deceleration determination unit 528 determines whether the deceleration condition is met. Specifically, it determines whether the bucket 23 has entered the soil pile Q, causing the vehicle body to experience a reaction force from the soil pile Q, thus sufficiently decelerating it. Here, refer to... Figure 6 The "deceleration condition" will be explained.

[0127] Figure 6 It is a graph showing the time variation of the acceleration of wheel loader 1 at the start of the excavation operation.

[0128] When performing excavation work, the wheel loader 1 travels towards the mound Q at a speed of approximately 10 km / h, and gradually decelerates to a speed of less than 2 km / h as it approaches the mound Q. In this situation, if... Figure 6 As shown in the diagram, every 3.0 to 3.8 seconds, the positive value of the differential of the vehicle speed, i.e., the acceleration, decreases in the negative direction. In other words, the negative value of the differential of the vehicle speed, i.e., the deceleration (negative acceleration), increases.

[0129] Furthermore, when the bucket 23 contacts (enters) the soil pile Q, the acceleration immediately changes from its minimum value to an increase. That is, when the bucket 23 contacts the soil pile Q, causing the vehicle body to experience a reaction force from the soil pile Q, the deceleration reaches its maximum value, and then the deceleration immediately decreases. Based on this relationship between vehicle speed and deceleration, the deceleration determination unit 528 can determine whether the bucket 23 has entered the soil pile Q, causing the vehicle body to experience a reaction force from the soil pile Q and thus sufficiently decelerate.

[0130] Therefore, the "deceleration condition" is when the vehicle speed V is below the speed at which the bucket 23 will enter the soil pile Q, and the deceleration changes from its maximum value to a decrease (acceleration changes from its minimum value to an increase). For example, the deceleration determination unit 528 determines whether the vehicle speed V obtained in the data acquisition unit 51 is below 2 km / h and whether the deceleration changes from the maximum value when the vehicle speed V is below 2 km / h to a deceleration Ath of 0.6 times. Figure 6 (The above is marked with ▲ in the chart).

[0131] Furthermore, the excavation auxiliary controller 5 records the lifting arm angle α obtained in the data acquisition unit 51 as the lifting arm reference angle αs when the deceleration determination unit 528 determines that the deceleration condition is met in the storage unit 55. That is, the posture (state) of the working device 2 when the deceleration determination unit 528 determines that the deceleration condition is met becomes the reference.

[0132] Based on the determination results in the excavation start determination unit 524 and the determination results in the lifting arm posture determination unit 527, the command signal output unit 53 outputs a lifting command signal to the lifting arm solenoid control valve 481 as a command signal related to the lifting action of the lifting arm 21.

[0133] In addition, the command signal output unit 53 outputs or stops outputting a tilt command signal as a command signal related to the tilting action (including full tilting action) of the bucket 23 to the bucket solenoid control valve 482 based on the determination results of the bucket posture determination unit 526 and the lifting arm posture determination unit 527.

[0134] If the processing stage counting unit 54 determines in the excavation start determination unit 524 that the excavation start condition is met, it sets the excavation auxiliary control processing stage to "1". In addition, if the processing stage counting unit 54 determines in the deceleration determination unit 528 that the deceleration condition is met and records the lifting arm reference angle αs in the storage unit 55, it sets the excavation auxiliary control stage processing to "2".

[0135] Furthermore, the processing stage counting unit 54 sequentially sets processing stages 3 to 7 when the command signal output unit 53 outputs a tilt command signal to the bucket solenoid control valve 482, and when the command signal output unit 53 stops outputting the tilt command signal to the bucket solenoid control valve 482.

[0136] The storage unit 55 is a memory that stores the predetermined angle threshold βth, the first angle threshold β1, the second angle threshold β2, the third angle threshold β3, the lifting arm reference angle αs, the first rising angle threshold αr1, the second rising angle threshold αr2, the third rising angle threshold αr3, the predetermined pedaling amount threshold SAth, the predetermined bottom pressure threshold PLbth, the predetermined first pressure threshold Pth, the predetermined speed threshold Vth, and the predetermined upper limit pressure Prlim.

[0137] (Processing in the excavation auxiliary controller 5)

[0138] Next, refer to Figures 7 to 16 The specific processing flow executed within the excavation auxiliary controller 5 is explained.

[0139] Figure 7 This is a flowchart representing the process executed by the excavation assistance controller 5. Figure 8 It means Figure 7 The subsequent process X in the flowchart shown. Figure 9 It means Figure 8 The subsequent process Y in the flowchart shown. Figures 10-16 This indicates that the excavation auxiliary controller 5 is executing. Figures 7-9 The flowchart shown illustrates the state of the posture change of the working device 2 under the given conditions. Specifically, Figure 10 This schematically represents the execution of the excavation auxiliary controller 5. Figures 7-9 A diagram showing the initial posture of the working device under the processing conditions. Figure 11 It is a schematic representation in Figure 8 The diagram shows the posture of the working device 2 when it enters the "Yes" state in step S616. Figure 12 It is a schematic representation in Figure 8 The diagram shows the posture of the working device 2 when it enters the "Yes" state in step S620. Figure 13 It is a schematic representation in Figure 8 The diagram shows the posture of the working device 2 when it enters the "Yes" state in step S625. Figure 14 It is a schematic representation in Figure 9 The diagram shows the posture of the working device 2 when it enters the "Yes" state in step S629. Figure 15 It is a schematic representation in Figure 9 The diagram shows the posture of the working device 2 when it enters the "Yes" state in step S633. Figure 16 It is a schematic representation in Figure 9 The diagram shows the posture of the working device 2 when it enters the "Yes" state in step S637.

[0140] like Figure 7As shown, in the excavation assistance controller 5, firstly, the start determination unit 521 determines whether the excavation assistance control system is started (step S601). Specifically, in step S601, the start determination unit 521 determines whether an activation signal from the excavation assistance start switch has been obtained in the data acquisition unit 51. At this time, the working device 2 is... Figure 10 The initial posture shown.

[0141] If it is determined in step S601 that the excavation auxiliary control system has been started (step S601 / Yes), the excavation preparation determination unit 522 determines whether the excavation preparation conditions are met (step S602).

[0142] On the other hand, if it is determined in step S601 that the excavation auxiliary control system has not been started (step S601 / No), that is, if the data acquisition unit 51 does not obtain an activation signal from the excavation auxiliary start switch, the process will not proceed to the next step S602 until the data acquisition unit 51 obtains an activation signal from the excavation auxiliary start switch and the excavation auxiliary control system is started.

[0143] In step S602, the excavation preparation determination unit 522 determines whether the bucket angle β calculated based on the boom angle α and the double boom crank angle γ obtained from the data acquisition unit 51 is within a predetermined angle threshold βth of the ground contact surface of the wheel loader 1 (whether the working device 2 is in an excavation posture), whether the accelerator pedal pedal pressure SA obtained from the data acquisition unit 51 is above a predetermined pedal pressure threshold SAth (whether the operator intends to perform excavation work), and whether the bottom pressure PLb of the boom cylinders 22L and 22R obtained from the data acquisition unit 51 is less than a predetermined bottom pressure threshold PLbth (whether the bucket 23 is in an unloaded state).

[0144] If the excavation preparation conditions (0<β≤βth, SA≥SAth, and PLb<PLbth) are met in step S602 (step S602 / Yes), the stop request determination unit 523 determines whether there is a request to stop the excavation auxiliary control based on the brake pedal depressing amount SB obtained in the data acquisition unit 51 (step S603).

[0145] On the other hand, if it is determined in step S602 that the excavation preparation conditions (β>βth, SA<SAth or PLb≥PLbth) are not met (step S602 / No), the process does not proceed to the next step S603 until the excavation preparation conditions are met.

[0146] If, in step S603, it is determined that there is no operation of the brake pedal 123 and there is no request to stop the digging assist control (step S603 / Yes), the digging start determination unit 524 determines whether the digging start condition is met (step S604).

[0147] On the other hand, if in step S603 it is determined that there is operation of the brake pedal 123 and a request is made to stop the excavation assist control (step S603 / No), the process returns to step S601 and repeats.

[0148] In step S604, the excavation start determination unit 524 determines whether the sum of the pressure PL applied to the two lifting arm cylinders 22L and 22R and the pressure PB applied to the bucket cylinder 24 is greater than a predetermined first pressure threshold Pth, whether the vehicle speed V obtained in the data acquisition unit 51 is less than a predetermined speed threshold Vth, and whether the external force F acting on the vehicle body is greater than or equal to a predetermined force threshold Fth.

[0149] If, in step S604, it is determined that the excavation start conditions (P > Pth, V ≤ Vth, and F ≥ Fth) are met (step S604 / Yes), the processing stage counter unit 54 sets the excavation auxiliary control processing stage 1 (step S605). Next, the command signal output unit 53 outputs a rising command signal to the lifting arm solenoid control valve 481 (step S606). As a result, the lifting arm 21 begins to rise.

[0150] If the boom 21 begins to rise, the bucket 23 also rises off the ground, and the bucket angle β increases. As a result, the weight of the cargo entering the bucket 23 is pressed down towards the ground (downward). Consequently, the boom cylinders 22L and 22R are also pressed down towards the ground (downward), thus increasing the force of contact between the front wheel 11A and the ground, preventing wheel 11 from slipping.

[0151] Furthermore, after the bucket 23 contacts the soil pile Q, as time passes, the working device 2 advances deeper into the soil pile Q. Therefore, the lifting motion of the boom 21 also increases over time, which can be adjusted to further prevent slippage. On the other hand, in order to prevent the working device 2 from raising the boom 21 before it has fully penetrated into the soil pile Q, the lifting motion of the boom 21 can be reduced in a manner inversely proportional to the rate of change of the boom angle α.

[0152] Next, the stop request determination unit 523 determines again whether there is a request to stop the excavation assist control based on the brake pedal depressing amount SB obtained in the data acquisition unit 51 (step S607).

[0153] If, in step S607, it is determined that there is no operation of the brake pedal 123 and there is no request to stop the digging auxiliary control (step S607 / Yes), the travel direction determination unit 525 determines whether the wheel loader 1 is moving forward based on the switching signal obtained in the data acquisition unit 51 (step S608).

[0154] On the other hand, if in step S607 it is determined that there is operation of the brake pedal 123 and a request is made to stop the excavation assist control (step S607 / No), proceed to... Figure 9 In step S638, the command signal output unit 53 stops outputting the lifting command signal for the boom solenoid control valve 481 and the tilting command signal for the bucket solenoid control valve 482, respectively (step S638). As a result, the operation of the working device 2 stops.

[0155] In addition, during the initial Figures 7-9 In the case of the excavation auxiliary controller 5 shown in the process, in the processing before step S607, only the lifting command signal is output to the lifting arm solenoid control valve 481. Therefore, in step S638, only the output of the lifting command signal to the lifting arm solenoid control valve 481 is stopped.

[0156] If it is determined in step S608 that the wheel loader 1 is moving forward (step S608 / Yes), the bucket posture determination unit 526 determines whether the bucket angle β obtained in the data acquisition unit 51 is smaller than the third angle threshold β3 (step S609).

[0157] On the other hand, if it is determined in step S608 that the wheel loader 1 is not moving forward, that is, the wheel loader 1 is moving backward or stopped (step S608 / No), then proceed to... Figure 9 In step S634, the command signal output unit 53 outputs a full tilt command signal to the solenoid control valve 482 for the bucket (step S634).

[0158] That is, when the excavation auxiliary controller 5 obtains a switching signal related to reversing or a switching signal related to stopping in the data acquisition unit 51 during the excavation auxiliary control, it controls the bucket 23 to be in a fully tilted state regardless of the posture of the bucket 23.

[0159] If it is determined in step S609 that the bucket angle β is smaller than the third angle threshold β3 (β < β3) (step S609 / Yes), the processing stage counting unit 54 determines whether the processing stage of the excavation auxiliary control is "1" (step S610).

[0160] On the other hand, if in step S609 it is determined that the bucket angle β is greater than or equal to the third angle threshold β3 (β≥β3) (step S609 / No), proceed to... Figure 9 In step S634, the command signal output unit 53 outputs a full tilt command signal to the solenoid control valve 482 of the bucket (step S634). That is, in step S609, it is determined whether the bucket 23 is in the final posture. If it is determined in step S609 that the bucket 23 is in the final posture, the control is performed so that the bucket 23 is in a full tilt state.

[0161] If the processing stage of the excavation auxiliary control is determined to be "1" in step S610 (step S610 / Yes), the deceleration determination unit 528 determines whether the deceleration condition is met (step S611).

[0162] On the other hand, if it is determined in step S610 that the processing stage of the excavation auxiliary control is not "1" (step S610 / No), then proceed to... Figure 8 In step S615, the processing stage counting unit 54 determines whether the processing stage of the excavation auxiliary control is "2" (step S615).

[0163] In step S611, the deceleration determination unit 528 determines whether the vehicle speed V obtained in the data acquisition unit 51 is below the speed before the bucket 23 enters the soil pile Q, and determines whether the acceleration of the vehicle speed V changes from a minimum value to an increase, that is, whether the deceleration changes from a maximum value to a decrease.

[0164] If the deceleration condition is determined to be met in step S611 (step S611 / Yes), the excavation assist controller 5 records the lifting arm angle α obtained in the data acquisition unit 51 at this time as the lifting arm reference angle αs in the storage unit 55 (step S612). Next, the processing stage counting unit 54 sets the processing stage 2 of the excavation assist control (step S613).

[0165] On the other hand, if it is determined in step S611 that the deceleration condition is not met (step S611 / No), it can be said that the bucket 23 has not fully entered the soil pile Q. Therefore, the command signal output unit 53 continues to output the rising command signal to the lifting arm using the electromagnetic control valve 481 (step S614), and then returns to step S607 to repeat the process.

[0166] like Figure 8As shown, when processing stage 2 is set in the processing stage counting unit 54 (step S615 / Yes), the lifting arm posture determination unit 527 determines whether the lifting arm rising angle αr is greater than or equal to the first rising angle threshold αr1 or whether the bottom pressure PLb of the lifting arm cylinder 22 is greater than or equal to the predetermined upper limit pressure Prlim (step S616). Furthermore, if processing stage 2 is not set in the processing stage counting unit 54 (step S615 / No), the process proceeds to step S619 to determine whether processing stage 3 is set.

[0167] In step S616, as Figure 11 As shown, when it is determined that the lifting arm's rising angle αr is greater than or equal to the first rising angle threshold αr1 (αr≥αr1) or the bottom pressure PLb of the lifting arm cylinder 22 is greater than or equal to the predetermined upper limit pressure Prlim (PLb≥Prlim) (step S616 / Yes), the command signal output unit 53 outputs a tilt command signal to the bucket solenoid control valve 482 (step S617). Next, the processing stage counter unit 54 sets the processing stage 3 of the digging auxiliary control (step S618).

[0168] On the other hand, if in step S616 it is determined that the lifting arm rising angle αr is less than the first rising angle threshold αr1 (αr < αr1) and the bottom pressure PLb of the lifting arm cylinder 22 is less than the predetermined upper pressure Prlim (PLb < Prlim) (step S616 / No), return to step S614 to repeat the process.

[0169] Next, if processing stage 3 is set in the processing stage counting unit 54 (step S619 / Yes), it is determined whether the bucket angle β is greater than or equal to the first angle threshold β1 (step S620). Furthermore, if processing stage 3 is not set in the processing stage counting unit 54 (step S619 / No), the process proceeds to step S622, where it is determined whether processing stage 4 is set (step S624).

[0170] In step S620, as Figure 12 As shown, when it is determined that the bucket angle β is greater than or equal to the first angle threshold β1 (β≥β1) (step S620 / Yes), the command signal output unit 53 stops outputting the tilt command signal to the bucket solenoid control valve 482 (step S621). Next, the processing stage counter unit 54 sets the processing stage 4 of the digging auxiliary control (step S622).

[0171] On the other hand, if it is determined in step S620 that the bucket angle β is less than the first angle threshold β1 (β < β1) (step S620 / No), that is, if it is determined that the posture of the bucket 23 is tilted forward compared to the final posture, the command signal output unit 53 continues to output a tilt command signal to the bucket solenoid control valve 482 (step S623), and then returns to step S607 to repeat the process. Furthermore, at this time, the command signal output unit 53 also continues to output a rise command signal to the boom solenoid control valve 481.

[0172] When processing stage 4 is set in processing stage counting unit 54 (step S624 / Yes), lifting arm posture determination unit 527 determines whether the lifting arm rising angle αr is greater than or equal to the second rising angle threshold αr2 or whether the bottom pressure PLb of lifting arm cylinder 22 is greater than or equal to the predetermined upper limit pressure Prlim (step S625).

[0173] Furthermore, if processing stage 4 is not set in the processing stage counting unit 54 (step S624 / No), proceed to... Figure 9 In step S628, it is determined whether processing stage 5 has been set.

[0174] In step S625, as Figure 13 As shown, if it is determined that the lifting arm's rising angle αr is greater than or equal to the second rising angle threshold αr2 (αr≥αr2) or the bottom pressure PLb of the lifting arm cylinder 22 is greater than or equal to the predetermined upper limit pressure Prlim (PLb≥Prlim) (step S625 / Yes), the command signal output unit 53 outputs a tilt command signal to the bucket solenoid control valve 482 again (step S626). Next, the processing stage counter unit 54 sets the processing stage 5 of the digging auxiliary control (step S627).

[0175] On the other hand, in step S625, if it is determined that the lifting arm rising angle αr is less than the second rising angle threshold αr2 (αr < αr2) and the bottom pressure PLb of the lifting arm cylinder 22 is less than the predetermined upper pressure Prlim (PLb < Prlim) (step S625 / No), the process returns to step S614 and is repeated.

[0176] like Figure 9 As shown, if processing stage 5 is set in the processing stage counting unit 54 (step S628 / Yes), it is determined whether the bucket angle β is greater than or equal to the second angle threshold β2 (step S629). Furthermore, if processing stage 5 is not set in the processing stage counting unit 54 (step S628 / No), the process proceeds to step S632 to determine whether processing stage 6 is set.

[0177] In step S629, as Figure 14As shown, when it is determined that the bucket angle β is greater than or equal to the second angle threshold β2 (β≥β2) (step S629 / Yes), the command signal output unit 53 stops outputting the tilt command signal to the bucket solenoid control valve 482 (step S630). Next, the processing stage counter unit 54 sets the processing stage 6 of the digging auxiliary control (step S631).

[0178] On the other hand, if it is determined in step S629 that the bucket angle β is less than the second angle threshold β2 (β<β2) (step S629 / No), return to step S623 and repeat the process.

[0179] Next, if processing stage 6 is set in the processing stage counting unit 54 (step S632 / Yes), the lifting arm posture determination unit 527 determines whether the lifting arm rising angle αr is greater than or equal to the third rising angle threshold αr3 or whether the bottom pressure PLb of the lifting arm cylinder 22 is greater than or equal to the predetermined upper limit pressure Prlim (step S633). Furthermore, if processing stage 6 is not set in the processing stage counting unit 54 (step S632 / No), the process proceeds to step S636 to determine whether processing stage 7 is set.

[0180] In step S633, as Figure 15 As shown, when it is determined that the lifting arm's rising angle αr is greater than or equal to the third rising angle threshold αr3 (αr≥αr3) or the bottom pressure PLb of the lifting arm cylinder 22 is greater than or equal to the predetermined upper limit pressure Prlim (PLb≥Prlim) (step S633 / Yes), the command signal output unit 53 outputs a full tilt command signal to the bucket solenoid control valve 482 (step S634). Next, processing stage 7 is set in the processing stage counter unit 54 (step S635).

[0181] On the other hand, if in step S633 it is determined that the lifting arm rising angle αr is less than the third rising angle threshold αr3 (αr<αr3) and the bottom pressure PLb of the lifting arm cylinder 22 is less than the predetermined upper pressure Prlim (PLb<Prlim) (step S633 / Yes), the process returns to step S614 and is repeated.

[0182] Next, if processing stage 7 is set in processing stage counting unit 54 (step S636 / Yes), bucket posture determination unit 526 determines whether bucket 23 is in a fully tilted state based on bucket angle β calculated from boom angle α and double boom crank angle γ obtained in data acquisition unit 51 (step S637).

[0183] Furthermore, if processing stage 7 is not set in the processing stage counting unit 54 (step S636 / No), the process proceeds to step S638, where the command signal output unit 53 stops outputting the tilt command signal for the bucket solenoid control valve 482 and the rise command signal for the boom solenoid control valve 481, respectively.

[0184] In step S637, as Figure 16 As shown, when it is determined that the bucket 23 is in a fully tilted state (step S637 / Yes), the command signal output unit 53 stops outputting the tilt command signal for the solenoid control valve 482 for the bucket and the rise command signal for the solenoid control valve 481 for the boom (step S638), and the excavation auxiliary control process ends.

[0185] On the other hand, in step S637, if it is determined that the bucket 23 is not in a fully tilted state (step S637 / No), the process returns to step S623 and is repeated.

[0186] Thus, in the excavation auxiliary controller 5, when the "start condition" is met—that the lifting angle αr of the boom 21 is at or above a predetermined lifting angle threshold (first lifting angle threshold αr1, second lifting angle threshold αr2, or third lifting angle threshold αr3) or the bottom pressure PLb of the boom cylinder 22 is at or above the upper limit pressure Prlim—the output of the tilt command signal to the bucket solenoid control valve 482 is "started." Conversely, when the "stop condition" is met—that the bucket angle β of the bucket 23 is at or above a predetermined angle threshold (first angle threshold β1 or second angle threshold β2)—the output of the tilt command signal to the bucket solenoid control valve 482 is "stopped."

[0187] Furthermore, during the period before the bucket 23 reaches the predetermined posture (equivalent to the aforementioned "final posture"), the tilt command signal for the solenoid control valve 482 for the bucket is repeatedly initiated and stopped based on these start and stop conditions. In other words, the movement control of the boom 21 and bucket 23 is performed in such a way that the bucket angle β becomes a preset target angle, corresponding to the determination results of the start and stop conditions. As a result, in the wheel loader 1, regardless of the size and shape of the soil pile Q that is the object of the operation, or the actions of the wheel loader 1 before the start of excavation, the cargo can be fully loaded into the bucket 23.

[0188] Specifically, in steps S620 and S629, the bucket angle β is maintained at the first angle threshold β1 and the second angle threshold β2, respectively, preventing the bucket 23 from unnecessarily over-erecting. Therefore, the cargo can be pressed against the bottom surface of the bucket 23 and stored within it using this force, while also allowing sufficient room for the bucket 23 to move during the final full tilt. Furthermore, by imparting inertia to the cargo near the opening (front) of the bucket 23 during the final full tilt, causing it to move inwards towards the inside of the bucket 23, it is possible to suppress cargo spillage from the bucket 23 during handling operations after excavation, thereby improving operational efficiency.

[0189] Furthermore, in step S609, when the bucket angle β reaches the third angle threshold β3, that is, when the posture of the bucket 23 is the final posture, the digging auxiliary controller 5 does not cause the bucket 23 to tilt further, but outputs a full tilt command signal to the bucket solenoid control valve 482 to cause the bucket 23 to tilt fully. Therefore, sufficient inertia can be given to the cargo in the bucket 23 to move it to the inside of the bucket 23.

[0190] Furthermore, in this embodiment, in step S604, it is determined whether the wheel loader 1 is subjected to force from the soil pile Q, i.e., whether the bucket 23 is in contact (enters) with the soil pile Q, by determining whether the force F applied to the vehicle body from the outside is above a predetermined force threshold Fth when the vehicle body is not accelerating relative to the output of the engine 40. This allows for highly accurate determination of whether the wheel loader 1 has started digging operations, and for example, it can suppress misjudgments related to bulldozing operations for leveling the ground.

[0191] The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments and modifications described above, and includes various other modifications. For example, the embodiments and modifications described above have been detailed for ease of understanding and explanation of the present invention, and are not necessarily limited to having all the described structures. Furthermore, a portion of the structure of this embodiment can be replaced with the structure of other embodiments, and it is also possible to add structures of other embodiments to the structure of this embodiment. Moreover, regarding a portion of the structure of this embodiment, other structures can be added, deleted, or replaced.

[0192] For example, in the above embodiment, the bucket 23 is brought to a fully tilted state by three tilting actions, but it is not limited to this. The present invention can also be applied when the bucket 23 is brought to a fully tilted state by one tilting action or by four or more tilting actions.

[0193] In addition, in the above embodiment, the driving device 401 is a torque converter type, but it is not limited to this and can also be an HST type.

[0194] Symbol Explanation

[0195] 1: Wheel loader

[0196] 5: Excavation auxiliary controller (controller)

[0197] 21: Lifting arm,

[0198] 22: Lifting boom cylinder,

[0199] 23: Bucket,

[0200] 24: Bucket cylinder,

[0201] 31: Lifting arm angle sensor (lifting arm posture sensor / bucket posture sensor)

[0202] 32: Dual-arm crank angle sensor (bucket posture sensor)

[0203] 38B: Bottom pressure sensor (pressure sensor) for lifting arm.

[0204] 40: Engine,

[0205] 41: Torque converter

[0206] 100: Mound of earth (object of the operation)

[0207] 122: Forward / Reverse Switch (Forward / Reverse Switching Device)

[0208] 401: Driving drive unit

[0209] 481: Electromagnetic control valve for lifting arm

[0210] 482: Electromagnetic control valve for bucket.

Claims

1. A wheel loader, comprising: A lifting arm is mounted at the front of the vehicle body and rotates vertically relative to the vehicle body. The bucket, which is installed at the front end of the lifting arm, digs up the work object by tilting backward relative to the vehicle body through an upward rotation relative to the lifting arm. A lifting arm cylinder that drives the lifting arm; Bucket cylinder, which drives the bucket; The lifting arm uses an electromagnetic control valve, which controls the lifting arm cylinder; A solenoid control valve for the bucket, which controls the bucket cylinder; and The controller controls the solenoid control valves for the lifting arm and the bucket, respectively. Its features are, The wheel loader has the following features: A pressure sensor that detects the bottom pressure of the lifting arm cylinder; A bucket posture sensor that detects the posture of the bucket; and A lifting arm posture sensor detects the posture of the lifting arm. When the controller detects that the bottom pressure detected by the pressure sensor has reached a first pressure threshold equivalent to the bottom pressure of the lifting arm cylinder in a state where the lifting arm is not in motion and the bucket is in contact with the work object, the controller outputs a command signal related to the lifting arm's upward movement via the electromagnetic control valve. After the controller starts outputting command signals related to the lifting arm's rising motion to the solenoid control valve of the lifting arm, if the lifting arm's rising amount, based on the lifting arm's posture detected by the lifting arm posture sensor, is greater than or equal to a predetermined rising amount threshold, or if the bottom pressure of the lifting arm cylinder detected by the pressure sensor is greater than or equal to a second pressure threshold that is greater than the first pressure threshold, then the controller outputs command signals related to the bucket's tilting motion to the solenoid control valve of the bucket. When the bucket posture sensor detects that the bucket is tilted forward compared to a predetermined posture, the controller continues to output command signals related to the lifting arm's rising motion to the boom solenoid control valve, and repeatedly starts and stops outputting command signals related to the bucket's tilting motion to the bucket solenoid control valve until the bucket reaches the predetermined posture. The predetermined posture is a full tilting motion that allows the excavated workpiece to be loaded into the inner side of the bucket. When the bucket posture detected by the bucket posture sensor has reached the predetermined posture, the controller outputs a command signal related to the full tilting action of the bucket via an electromagnetic control valve.

2. The wheel loader according to claim 1, characterized in that, The wheel loader includes an acceleration sensor that detects the acceleration of the vehicle body. The controller stores the posture of the lifting arm detected by the lifting arm posture sensor as a reference posture when the acceleration of the vehicle body detected by the acceleration sensor changes from a minimum value to an increase. The controller determines the lifting amount of the lifting arm based on the stored reference posture.

3. The wheel loader according to claim 1, characterized in that, The wheel loader includes a torque converter-type driving device comprising an engine mounted on the vehicle body and a torque converter that amplifies the torque transmitted from the engine. The controller calculates the force exerted on the vehicle body from the outside in its unaccelerated state based on the output torque of the torque converter, the rotational speed of the torque converter, the weight of the vehicle body, and the acceleration of the vehicle body. When the calculated force reaches a force threshold equivalent to the force exerted from the work object onto the vehicle body when the bucket contacts the work object, and the bottom pressure detected by the pressure sensor reaches the first pressure threshold, the controller outputs a command signal related to the lifting arm's rising action via an electromagnetic control valve.

4. The wheel loader according to claim 1, characterized in that, The wheel loader has a forward / reverse switching device for switching the vehicle body between forward and reverse directions. When the controller outputs a command signal related to the lifting action of the lifting arm to the solenoid control valve of the lifting arm, and receives a signal related to reversal or stop from the forward / reverse switching device, it outputs a command signal related to the full tilting action of the bucket to the solenoid control valve of the bucket.

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