Wheel loader

Abstract

Provided is a wheel loader capable of providing a good balance between a traction force and a digging force of a cargo handling work device when the operation of the cargo handling work device during digging is automatically controlled. A wheel loader (1) having a semi-automatic excavation mode function in which controllers (5), (5A), (5B) automatically control a travel drive device (3) and a cargo handling work device (2) in order to assist the operation of an operator, the semi-automatic excavation mode includes a first excavation mode in which the controllers (5), (5A), (5B) do not limit the rotational speed of the engine (30), and a second excavation mode in which the controllers (5), (5A), (5B) limit the rotational speed of the engine (30) such that the traction force generated by the travel drive device (3) is smaller than the first excavation mode. The controllers (5, 5A, 5B) switch the first excavation mode and the second excavation mode on the basis of the first to third mode selection switches (61-63) or the discharge pressure (Pa) of the hydraulic pump (33) immediately before the start of excavation work.

Description

Technical Field

[0001] The present invention relates to a wheel loader for performing excavation operations. Background Art

[0002] The wheel loader has a cargo handling device for excavating work objects such as soil, sand and minerals and loading them onto a dump truck etc. The cargo handling device has a lift arm mounted on the front of the vehicle body and rotatable in the up-down direction relative to the vehicle body, and a bucket mounted on the front end of the lift arm and rotatable in the up-down direction relative to the lift arm.

[0003] When performing excavation work, the operator needs to step on the accelerator pedal to move forward at a low speed, operate the operating lever to raise the bucket, and raise the lift arm to scoop up the work object. In order to reduce the operator's operating burden during such excavation work, some wheel loaders can perform so-called "semi-automatic excavation" in which the controller automatically controls the movement of the lift arm and bucket to perform excavation.

[0004] For example, Patent Document 1 discloses a wheel loader having a control device for controlling the tilting action (standing action) of the bucket and the raising action of the lifting arm. The control device starts the tilting action of the bucket based on the lifting force of the lifting arm and the vehicle speed, and ends the tilting action based on the amount of increase in the lifting force of the lifting arm from the time when the tilting action starts. In addition, the control device starts the raising action of the lifting arm based on the lifting force of the lifting arm, the vehicle speed, and the angle of the lifting arm, and ends the raising action based on the amount of increase in the lifting force of the lifting arm or the angle of the lifting arm from the start of the raising action of the lifting arm.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5700613 Summary of the invention

[0008] However, in the wheel loader described in Patent Document 1, the control device only performs control focusing on the timing of starting and ending the tilting action of the bucket and the raising action of the lift arm, thereby not considering the balance between the traction force (travel driving force) during excavation and the digging force of the cargo handling operation device.

[0009] When excavating, the wheel loader needs to push the work object into the bucket by moving forward while operating the cargo handling device to scoop up the work object. Therefore, the balance between the traction force and the digging force of the cargo handling device becomes important.

[0010] In the case of the wheel loader described in Patent Document 1, for example, when digging, if the traction force is too large relative to the digging force of the cargo handling device required for digging, the bucket will push the work object unnecessarily, and the bucket may be overloaded with the work object, resulting in an overloaded state. On the other hand, when digging, if the traction force is too small relative to the digging force of the cargo handling device required for digging, the vehicle body cannot move forward, and the bucket may not be pushed relative to the work object, and the work object may not enter the bucket. These operations to adjust the balance between the traction force and the digging force are entrusted to the operator, which requires skill and becomes a difficult operation for an unskilled operator. For example, an unskilled operator may output the traction force unnecessarily even if the traction force is output more than necessary, without thinking of reducing the traction force. In the state where the traction force is output unnecessarily, even if the operator operates the cargo handling device, it is overloaded and cannot smoothly perform digging.

[0011] Therefore, an object of the present invention is to provide a wheel loader capable of achieving a good balance between the traction force and the excavation force of the cargo handling work device when the operation of the cargo handling work device during excavation is automatically controlled.

[0012] In order to achieve the above-mentioned object, the wheel loader of the present invention comprises: a vehicle body; an engine mounted on the vehicle body; a travel drive device driven by the engine to drive the vehicle body; a travel operating device for operating the travel drive device; a hydraulically driven cargo handling device mounted on the vehicle body and excavating a work object; a hydraulic pump driven by the engine to supply working oil to a driving part of the cargo handling device; a cargo handling operating device for operating the cargo handling device; a controller for controlling the engine, the travel drive device, and the cargo handling device, respectively; and a mode selecting device for selecting a normal mode and a semi-automatic excavation mode, wherein the normal mode is a mode in which the controller controls the cargo handling device based on an operating signal output from the cargo handling operating device. mode, the semi-automatic excavation mode is a mode in which the controller automatically controls the travel drive device and the cargo loading and unloading operation device based on the operation signal output from the travel operation device in order to support the operator's operation, and the wheel loader is characterized in that the semi-automatic excavation mode has: a first excavation mode in which the controller does not limit the rotation speed of the engine; and a second excavation mode in which the controller limits the rotation speed of the engine in a manner that makes the traction force based on the travel drive device smaller than that in the first excavation mode, and the controller switches the first excavation mode and the second excavation mode based on a state in which the semi-automatic excavation mode has been selected by the mode selection device, or based on a state in which the semi-automatic excavation mode has been selected by the mode selection device, and a discharge pressure of the hydraulic pump immediately before the start of the excavation operation.

[0013] Effects of the Invention

[0014] According to the present invention, when the operation of the cargo handling device during excavation is automatically controlled, the balance between the traction force and the excavation force of the cargo handling device can be improved. Other problems, configurations, and effects than those described above will become clear from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an external appearance side view showing a configuration example of a wheel loader according to each embodiment of the present invention.

[0016] Figure 2 This is an explanatory diagram for explaining the flow of a series of cargo loading and unloading operations in a wheel loader.

[0017] Figure 3 It is a system configuration diagram showing an example of the configuration of a drive system of the wheel loader in the first embodiment.

[0018] Figure 4 This is a graph showing the relationship between vehicle speed and traction force at each speed level.

[0019] Figure 5 This is a functional block diagram showing the functions of the controller in the first embodiment.

[0020] Figure 6 This is a flowchart showing the flow of a process based on control in the semi-automatic excavation mode executed by the controller in the first embodiment.

[0021] Figure 7 This is a functional block diagram showing the functions of the controller in the second embodiment.

[0022] Figure 8 This is a flowchart showing the flow of a process based on control in the semi-automatic excavation mode executed by the controller in the second embodiment.

[0023] Fig. 9 This is a functional block diagram showing the functions of the controller in the third embodiment.

[0024] Fig.10 This is a flowchart showing the flow of a process based on control in the semi-automatic excavation mode executed by the controller in the third embodiment. DETAILED DESCRIPTION

[0025] The wheel loader according to each embodiment of the present invention is a work vehicle that performs cargo loading and unloading work, for example, excavating a work object such as earth, sand, or minerals and loading the work object onto a loading target such as a dump truck or a hopper.

[0026] <Schematic Configuration of Wheel Loader 1>

[0027] First, refer to Figure 1 The outline of the wheel loader 1 according to each embodiment of the present invention will be described.

[0028] Figure 1 It is an external appearance side view showing one configuration example of the wheel loader 1 according to each embodiment of the present invention.

[0029] The wheel loader 1 is an articulated working machine that is turned by bending the vehicle body near the center. A front frame 1A constituting the front part of the vehicle body and a rear frame 1B constituting the rear part of the vehicle body are connected to each other in a rotatable manner in the left-right direction by a central connector 10, and the front frame 1A is bent in the left-right direction relative to the rear frame 1B by a steering operation.

[0030] The vehicle body is provided with four wheels 11, two of which are front wheels 11A and are respectively provided on the left and right sides of the front frame 1A, and the remaining two wheels 11 are rear wheels 11B and are respectively provided on the left and right sides of the rear frame 1B. Figure 1In the figure, only the left front wheel 11A and the rear wheel 11B are shown among the four wheels 11. A hydraulically driven cargo handling device 2 is mounted on the front part of the front frame 1A.

[0031] The cargo handling operation device 2 includes: a lift arm 21 mounted on the front frame 1A; two lift arm hydraulic cylinders 22 driving the lift arm 21; a bucket 23 mounted on the front end of the lift arm 21; a bucket hydraulic cylinder 24 driving the bucket 23; and a bell crank 25 rotatably connected to the lift arm 21 and constituting a connecting rod mechanism between the bucket 23 and the bucket hydraulic cylinder 24. The two lift arm hydraulic cylinders 22 and the bucket hydraulic cylinder 24 are respectively equivalent to the driving parts of the cargo handling operation device 2. In addition, Figure 1 In FIG. 1 , only the lift arm hydraulic cylinder 22 arranged on the left side of the two lift arm hydraulic cylinders 22 arranged in the left-right direction of the vehicle body is indicated by a dotted line.

[0032] The two lift arm hydraulic cylinders 22 rotate the lift arm 21 in the up-down direction relative to the front frame 1A by extending and retracting the piston rod 220. The lift arm 21 rotates in the upward direction relative to the front frame 1A by extending the piston rod 220 of each lift arm hydraulic cylinder 22, and rotates in the downward direction relative to the front frame 1A by contracting the piston rod 220 of each lift arm hydraulic cylinder 22.

[0033] The bucket hydraulic cylinder 24 rotates the bucket 23 in the up-down direction relative to the lift arm 21 by extending and retracting the piston rod 240. The bucket 23 rotates upward relative to the lift arm 21 (tilt action) by extending the piston rod 240 of the bucket hydraulic cylinder 24, and rotates downward relative to the lift arm 21 (unloading action) by contracting the piston rod 240 of the bucket hydraulic cylinder 24.

[0034] The rear frame 1B is provided with a cab 12 for an operator to sit in, a machine room 13 that houses various equipment required for driving the wheel loader 1, and a counterweight 14 for maintaining a balance between the vehicle body and the cargo handling device 2 so that the vehicle body does not tip over. In the rear frame 1B, the cab 12 is arranged at the front, the counterweight 14 is arranged at the rear, and the machine room 13 is arranged between the cab 12 and the counterweight 14.

[0035] <Operation of the wheel loader 1 during cargo loading and unloading operation>

[0036] Next, refer to Figure 2 The operation of the wheel loader 1 during cargo loading and unloading work will be described.

[0037] Figure 2 It is an explanatory diagram for explaining the flow of a series of cargo loading and unloading operations in the wheel loader 1 .

[0038] In cargo handling operations, the wheel loader 1 first moves forward toward a pile of earth to be excavated while the bucket 23 is kept at a horizontal position to the ground by the operator's travel operation (state A). Then, the wheel loader 1 causes the bucket 23 to penetrate into the pile of earth by the operator's acceleration operation (state B).

[0039] Next, the wheel loader 1 tilts the bucket 23 while raising the lift arm 21 to excavate the soil pile (state C). This excavation requires an acceleration operation and a cargo handling operation (operation of the cargo handling device 2). In the wheel loader 1, in addition to the excavation performed manually by the operator performing these two operations, semi-automatic excavation can also be performed in which the operator only performs the acceleration operation and the cargo handling operation is automatically performed without relying on the operator's operation.

[0040] After excavation is completed, the wheel loader 1 moves the cargo loaded in the bucket 23 to the loading target through the operator's driving operation (state D). Furthermore, the wheel loader 1 causes the bucket 23 to perform an unloading operation through the operator's cargo loading and unloading operation, and discharges the cargo to the loading target (state E). The wheel loader 1 repeats this process. Figure 2 The operations in the illustrated states A to E are performed until a predetermined amount of cargo is loaded onto the loading destination.

[0041] Hereinafter, a specific system configuration of the wheel loader 1 equipped with the semi-automatic excavation function will be described according to each embodiment.

[0042] <First embodiment>

[0043] Reference Figure 3 to Figure 6 The system configuration of the first embodiment of the present invention will be described.

[0044] (Drive system of wheel loader 1)

[0045] First, refer to Figure 3 as well as Figure 4 The drive system of the wheel loader 1 will be described.

[0046] Figure 3 1 is a system configuration diagram showing an example of the configuration of the drive system of the wheel loader 1 according to the first embodiment. Figure 4 It is a graph showing the relationship between the vehicle speed S and the traction force F at each speed stage.

[0047] like Figure 3 As shown, in this embodiment, the wheel loader 1 controls the travel of the vehicle body by a torque converter type travel drive device 3. In the torque converter type travel drive device 3, the driving force of the engine 30 is transmitted to the plurality of wheels 11 via a torque converter 31 (hereinafter referred to as "torque converter 31") and a transmission 32.

[0048] The torque converter 31 is a fluid clutch composed of a driving impeller, a driven impeller, and a stationary impeller, and has a function of increasing the output torque relative to the input torque (torque transmitted from the engine 30), that is, a function of setting the torque ratio (= output torque / input torque) to 1 or more. This torque ratio decreases as the ratio of the rotation speed of the input shaft of the torque converter 31 to the rotation speed of the output shaft, that is, the torque converter speed ratio (= output shaft rotation speed / input shaft rotation speed), increases. As a result, the rotation speed of the engine 30 is changed and transmitted to the transmission 32.

[0049] The rotation speed of the input shaft of the torque converter 31 is detected by a first rotation speed sensor 31A attached to the input shaft of the torque converter 31. The first rotation speed sensor 31A detects the rotation speed of the engine 30 as the rotation speed of the input shaft of the torque converter 31.

[0050] The rotation speed of the output shaft of the torque converter 31 is detected by a second rotation speed sensor 31B attached to the output shaft of the torque converter 31. The second rotation speed sensor 31B detects the rotation speed after the speed change in the torque converter 31 as the rotation speed of the output shaft of the torque converter 31.

[0051] The gearbox 32 is composed of a plurality of gears, and the combination of the plurality of gears is controlled so that the gears are in the forward or reverse direction. Figure 4 The gear ratio corresponding to any one of the first to fourth speed stages shown is used to change the torque, rotation speed, and rotation direction of the output shaft of the torque converter 31 and transmit them to the plurality of wheels 11 .

[0052] The travel direction of the wheel loader 1, that is, the switching of the forward and reverse directions, is performed by the forward and reverse switching switch 41. The speed level ( Figure 4 The selection of the first to fourth speed stages (shown in FIG. 1 ) is performed by the shift switch 42. The forward / reverse switching switch and the shift switch 42 are respectively provided in the cab 12 (see FIG. 1 ). Figure 1 ).

[0053] like Figure 4 As shown, the speed levels of the transmission 32 are: in the first speed level, the maximum vehicle speed is set to S1, in the second speed level, the maximum vehicle speed is set to S2 which is greater than S1, in the third speed level, the maximum vehicle speed is set to S3 which is greater than S2, and in the fourth speed level, the maximum vehicle speed is set to S4 which is greater than S3 (S1<S2<S3<S4).

[0054] In this case, the traction force F of the vehicle body corresponding to the first to fourth speed levels is F1 in the first speed level, F2 which is smaller than F1 in the second speed level, F3 which is smaller than F2 in the third speed level, and F4 which is smaller than F3 in the fourth speed level (F1>F2>F3>F4). Therefore, the smaller the speed level, the smaller the maximum vehicle speed, but on the other hand, the traction force F of the vehicle body is greater. In addition, Figure 4 In the figure, the first speed level is indicated by a solid line, the second speed level is indicated by a dotted line, the third speed level is indicated by a dashed line, and the fourth speed level is indicated by a dashed double-dashed line.

[0055] The first speed level is the lowest speed level of the transmission 32 and is selected mainly when performing operations requiring traction, such as excavation and climbing operations. Figure 4 As shown, the maximum vehicle speed (= S1 ) in the first speed stage is the lowest speed among the first to fourth speed stages, but on the other hand, the traction force F (= F1 ) is the largest among the first to fourth speed stages.

[0056] The second speed level is a speed level set higher than the first speed level, which is the lowest speed level of the transmission 32, and is mainly selected during loading operations. Figure 4 As shown, when the maximum vehicle speed (= S2 ) in the second speed stage is faster than the first speed stage, the traction force F (= F2 ) is significantly smaller than that in the first speed stage.

[0057] The 3rd and 4th speed levels correspond to the medium to high speed levels and are mainly selected for handling operations. Figure 4 As shown, when the maximum vehicle speed in the third speed stage (= S3) is faster than the second speed stage, the traction force F (= F3) is smaller than that in the second speed stage. When the maximum vehicle speed in the fourth speed stage (= S4) is faster than the third speed stage, the traction force F (= F4) is smaller than that in the third speed stage.

[0058] When the wheel loader 1 travels, first, the operator steps on the accelerator pedal 43 provided in the cab 12. The engine 30 rotates thereby, and the input shaft of the torque converter 31 rotates along with the rotation of the engine 30. The accelerator pedal 43 corresponds to a travel operation device for operating the travel drive device 3.

[0059] The output shaft of the torque converter 31 rotates according to the set torque converter speed ratio, and the output torque from the torque converter 31 is transmitted to the plurality of wheels 11 via the transmission 32, the propeller shaft 15, and the axle 16, thereby the wheel loader 1 travels. The vehicle speed of the wheel loader 1 is detected by a vehicle speed sensor 15A mounted on the propeller shaft 15 as the rotation speed of the propeller shaft 15.

[0060] The engine 30 , the torque converter 31 , and the transmission 32 are each controlled based on a command signal output from the controller 5 .

[0061] The controller 5 outputs a command signal related to the target engine speed to the engine control unit 30A. The engine 30 is controlled according to the command signal related to the target engine speed acquired by the engine control unit 300. The target engine speed is proportional to the amount of depression of the accelerator pedal 43, and increases as the amount of depression of the accelerator pedal 43 increases. The amount of depression of the accelerator pedal 43 is detected by a depression amount sensor 43A installed on the accelerator pedal 43.

[0062] The controller 5 sets the torque converter speed ratio based on the input shaft rotation speed RS1 of the torque converter 31 detected by the first rotation speed sensor 31A and the output shaft rotation speed RS2 of the torque converter 31 detected by the second rotation speed sensor 31B, and outputs a command signal related to the set torque converter speed ratio to the torque converter control unit 310. The torque converter 31 is controlled according to the command signal related to the torque converter speed ratio obtained by the torque converter control unit 310.

[0063] The controller 5 selects a combination of multiple gears in the transmission 32 based on the travel direction switched by the forward / reverse switch 41 and the speed stage selected by the shift switch 42, and outputs a command signal related to the selected combination of multiple gears to the transmission control unit 320 (hereinafter referred to as "TM control unit 320"). The transmission 32 is controlled according to the command signal related to the combination of multiple gears acquired by the TM control unit 320.

[0064] In addition, the wheel loader 1 controls the operation of the cargo handling device 2 by a hydraulically driven cargo handling drive system. In the cargo handling drive system, the hydraulic oil discharged from the hydraulic pump 33 is supplied to the two lift arm hydraulic cylinders 22 and the bucket hydraulic cylinder 24 via the control valve unit 34, thereby operating the lift arm 21 and the bucket 23 respectively. Figure 3 In order to simplify the structure, only one of the two lift arm hydraulic cylinders 22 is shown in the figure.

[0065] The hydraulic pump 33 is driven by the engine 30, and supplies the hydraulic oil sucked from the hydraulic oil tank 330 to the two lift arm hydraulic cylinders 22 and the bucket hydraulic cylinder 24. In the present embodiment, the hydraulic pump 33 is a fixed displacement hydraulic pump, but it is not limited thereto, and may also be a variable displacement hydraulic pump whose discharge volume is controlled according to the tilt angle. The discharge pressure Pa of the hydraulic pump 33 is detected by a discharge pressure sensor 33A provided on the discharge side of the hydraulic pump 33.

[0066] In the present embodiment, the control valve unit 34 controls the flow (direction and flow rate) of the working oil supplied from the hydraulic pump 33 to the two lift arm hydraulic cylinders 22 and the bucket hydraulic cylinder 24, respectively, based on the operation amount of the operating levers 121 and 122 which are the cargo handling operation device for operating the cargo handling operation device 2, or based on the automatic control performed by the controller 5.

[0067] In addition, although Figure 3 Although not shown in the figure, the control valve unit 34 includes a control valve for controlling the flow of hydraulic oil supplied from the hydraulic pump 33 to the two lift arm hydraulic cylinders 22, and a control valve for controlling the flow of hydraulic oil supplied from the hydraulic pump 33 to the bucket hydraulic cylinder 24. In the following description, the operating lever 121 of the operating levers 121 and 122 is used for operating the lift arm 21, and the operating lever 122 is used for operating the bucket 23.

[0068] The pilot pressure generated according to the operation amount of the operating levers 121 and 122 acts on each control valve of the control valve unit 34. When the pilot pressure acts on each control valve, the internal spool moves according to the magnitude of the pilot pressure. This switches the flow of the hydraulic oil supplied from the hydraulic pump 33 to the two lift arm hydraulic cylinders 22 and the bucket hydraulic cylinder 24.

[0069] For example, when the control valves on the sides of the two lift arm hydraulic cylinders 22 are switched to a position where the hydraulic pump 33 is connected to the cylinder bottom chambers of the two lift arm hydraulic cylinders 22 and the working oil tank 330 is connected to the piston rod chambers of the two lift arm hydraulic cylinders 22, the piston rods 220 of the two lift arm hydraulic cylinders 22 are extended and the lift arm 21 rotates upward relative to the vehicle body.

[0070] On the other hand, when the control valves on the sides of the two lift arm hydraulic cylinders 22 are switched to a position where the hydraulic pump 33 is connected to the piston rod chambers of the two lift arm hydraulic cylinders 22 and the working oil tank 330 is connected to the cylinder bottom chambers of the two lift arm hydraulic cylinders 22, the piston rods 220 of the two lift arm hydraulic cylinders 22 contract and the lift arm 21 rotates downward relative to the vehicle body.

[0071] Furthermore, a cylinder bottom pressure sensor 22A is provided on the cylinder bottom chamber side of one lift arm hydraulic cylinder 22 , which detects the cylinder bottom pressure of the lift arm hydraulic cylinder 22 as the cylinder pressure applied to the lift arm hydraulic cylinder 22 .

[0072] Similarly, when the control valve on the bucket cylinder 24 side is switched to a position where the hydraulic pump 33 is connected to the cylinder bottom chamber of the bucket cylinder 24 and the hydraulic oil tank 330 is connected to the piston rod chamber of the bucket cylinder 24, the piston rod 240 of the bucket cylinder 24 extends and the bucket 23 performs a tilting action.

[0073] On the other hand, when the control valve on the bucket cylinder 24 side is switched to a position where the hydraulic pump 33 is connected to the piston rod chamber of the bucket cylinder 24 and the hydraulic oil tank 330 is connected to the cylinder bottom chamber of the bucket cylinder 24, the piston rod 240 of the bucket cylinder 24 contracts and the bucket 23 performs an unloading action.

[0074] The pilot pressure acting on the control valve unit 34 is controlled by the first to fourth solenoid valves 341 to 344. In addition, the first solenoid valve 341 and the second solenoid valve 342 control the pilot pressure acting on the control valves on the two lift arm hydraulic cylinders 22, and the third solenoid valve 343 and the fourth solenoid valve 344 control the pilot pressure acting on the control valve on the bucket hydraulic cylinder 24.

[0075] For example, when an operator operates the operating lever 121 of the lift arm 21, the operating direction and the operating amount are input as pilot signals to the controller 5. The controller 5 generates control signals based on the acquired pilot signals and outputs them to the first and second electromagnetic valves 341 and 342, respectively.

[0076] Similarly, when the operator operates the operating lever 122 of the bucket 23, the operating direction and the operating amount are input as pilot signals to the controller 5. The controller 5 generates control signals based on the acquired pilot signals and outputs them to the third solenoid valve 343 and the fourth solenoid valve 344, respectively.

[0077] In the present embodiment, the wheel loader 1 is equipped with various modes in which the controller 5 automatically controls each device in addition to the control of each device by manual operation by the operator for the purpose of improving the efficiency of the excavation work and the fuel efficiency.

[0078] Specifically, the wheel loader 1 is equipped with: a "driving mode" in which the controller 5 automatically controls the speed level during excavation; an "operation mode" in which the controller 5 automatically controls the rotational speed of the engine 30 according to the required fuel consumption; and a "semi-automatic excavation mode" in which the controller 5 automatically controls the travel drive device 3 and the cargo loading and unloading operation device 2 based on the operation signal output from the accelerator pedal 43 in order to support the operator's operation in the case of the above-mentioned semi-automatic excavation.

[0079] The driving mode includes, as setting modes, a first automatic mode in which the speed level during excavation is automatically reduced to the first speed level, and a second automatic mode in which the speed level during excavation is automatically reduced only to the second speed level. A first mode selection switch 61 for selecting the first automatic mode, the second automatic mode, and the driving mode off is provided in the cab 12. Information on the mode (the first automatic mode, the second automatic mode, or the mode off) selected by the first mode selection switch 61 is input to the controller 5 as a mode signal.

[0080] The operation mode has, as setting modes, an STD mode for limiting the rotation speed of the engine 30 and performing fuel-saving driving, and a P mode for not limiting the rotation speed of the engine 30. A second mode selection switch 62 for selecting the STD mode and the P mode is provided in the cab 12. Information related to the mode (STD mode or P mode) selected by the second mode selection switch 62 is input to the controller 5 as a mode signal. In addition, in the operation mode, the P mode is equivalent to turning off the restriction (STD mode) of the rotation speed of the engine 30, and thus, the second mode selection switch 62 is not provided with a turning off of the operation mode.

[0081] In the travel mode and the operation mode, the cargo handling operation device 2 controls the operation based on the operation amount of the operating levers 121 and 122. That is, when the travel mode is selected by the first mode selection switch 61, or when the operation mode is selected by the second mode selection switch 62, the operation of the cargo handling operation device 2 becomes a manual operation by the operator. In this way, both the travel mode and the operation mode correspond to the normal mode in which the operation of the cargo handling operation device 2 is controlled based on the operation amount of the operating levers 121 and 122.

[0082] The semi-automatic excavation mode is a mode in which the controller 5 automatically controls the rotation speed of the engine 30 and the speed level of the transmission 32 according to the specific gravity and water content of the work object, and has a heavy excavation mode as a first excavation mode and a light excavation mode as a second excavation mode as setting modes.

[0083] The heavy excavation mode is a setting mode that combines the first automatic mode in the travel mode and the P mode in the work mode. The controller 5 automatically reduces the speed of the transmission 32 during excavation to the first speed level, which is the lowest speed level, without limiting the rotation speed of the engine 30.

[0084] On the other hand, the light excavation mode is a setting mode that combines the second automatic mode in the driving mode and the STD mode in the working mode, and is a mode in which the controller 5 automatically reduces the speed level of the transmission 32 during excavation to the second speed level only and limits the rotation speed of the engine 30 in such a manner that the traction force based on the driving drive device 3 is less than that in the heavy excavation mode.

[0085] The heavy excavation mode is selected when the specific gravity and water content of the work object are greater than those of the light excavation mode, that is, when the greatest possible traction force is required. For example, the heavy excavation mode is selected when the excavation specific gravity is 2.0 [t / m 3 ] degree of clay soil and specific gravity 2.5[t / m 3 ] is selected when digging work objects such as pebbles of a certain degree, and when digging work objects that are rich in water and moist due to rainfall.

[0086] The light excavation mode is selected when the specific gravity and water content of the work object are less than those of the heavy excavation mode, that is, when traction is not required. For example, the light excavation mode is selected when the excavation specific gravity is 1.3 [t / m 3 ] degree of coal and specific gravity 1.7[t / m 3 ] is selected in the case of working objects such as gravel with a certain degree of sand, and in the case of working objects in a dry state due to evaporation of moisture inside the excavation.

[0087] When the work object is a relatively heavy object such as clay or ore and is wet, if the traction force is too small for the digging force of the cargo handling work device 2 required for digging, the vehicle body cannot move forward, and the bucket 23 cannot be pushed into the work object, making it difficult to get the work object into the bucket 23. Therefore, in this case, the heavy digging mode is selected to increase the traction force of the wheel loader 1, so that the vehicle body can move forward and the work object can be pushed into the bucket 23.

[0088] On the other hand, when the work object is a relatively heavy object such as coal or gravel and is dry, if the traction force is too large for the digging force of the cargo handling device 2 required for digging, the bucket 23 will be pushed into the work object unnecessarily, and the work object will be excessively loaded in the bucket 23, resulting in an overloaded state. In addition, if the bucket 23 is pushed deeply into the work object (earth pile), there is a possibility that the digging force of the cargo handling device 2 is insufficient, resulting in the wheel loader 1 being unable to lift the bucket 23.

[0089] Therefore, in these cases, the light excavation mode is selected and the traction force of the wheel loader 1 is reduced, thereby eliminating overloading of the work object into the bucket 23. In this case, by reducing the traction force of the wheel loader 1 as much as possible, fuel efficiency can also be improved.

[0090] As described above, in the semi-automatic excavation mode, unlike the above-mentioned travel mode and operation mode, the cargo handling operation device 2 is automatically controlled by the controller 5 according to the specific gravity and water content of the operation object.

[0091] Specifically, when the semi-automatic excavation mode is selected by the third mode selection switch 63 and the excavation operation is started and the excavation operation is being performed in the semi-automatic excavation mode, the controller 5 generates a control signal based on the selected setting mode (heavy excavation mode or light excavation mode) and outputs the control signal to the first to fourth solenoid valves 341 to 344. As a result, the lift arm 21 and the bucket 23 are automatically controlled to operate in the heavy excavation mode or the light excavation mode without depending on the operation of the operating levers 121 and 122, respectively.

[0092] Furthermore, the semi-automatic excavation mode does not necessarily have only two modes, the heavy excavation mode and the light excavation mode. For example, when the wheel loader 1 handles many types of work objects, it may have three or more setting modes corresponding to the respective specific gravities.

[0093] A third mode selection switch 63 for turning on either the heavy excavation mode or the light excavation mode in the semi-automatic excavation mode and for turning off the semi-automatic excavation mode is provided in the cab 12. Information on the mode (heavy excavation mode, light excavation mode, or mode off) selected by the third mode selection switch 63 is input to the controller 5 as a mode signal.

[0094] The first mode selection switch 61, the second mode selection switch 62, and the third mode selection switch 63 are one form of a mode selection device for selecting the semi-automatic excavation mode and the normal mode. In this embodiment, the mode selection device is composed of three mode selection switches 61 to 63, but is not limited to this. For example, the travel mode, the working mode, and the automatic excavation mode can also be selected by one device.

[0095] In addition, in the present embodiment, the third mode selection switch 63 is an input device capable of selecting the heavy excavation mode and the light excavation mode, but is not limited thereto, and may be a device for selecting only the semi-automatic excavation mode (turning the semi-automatic excavation mode on and off). This will be described in the second embodiment and the third embodiment.

[0096] (Functional Structure of Controller 5)

[0097] Next, refer to Figure 5 The functional configuration of the controller 5 will be described.

[0098] Figure 5 This is a functional block diagram showing the functions of the controller 5 according to the first embodiment.

[0099] The controller 5 is composed of a CPU, a RAM, a ROM, a HDD, an input I / F, and an output I / F connected to each other via a bus. Various operating devices such as the operating levers 121 and 122, the forward / reverse switch 41, the shift switch 42, and the first to third mode selection switches 61 to 63, and various sensors such as the vehicle speed sensor 15A, the discharge pressure sensor 33A, the cylinder bottom pressure sensor 22A, the stepping amount sensor 43A, the first rotation speed sensor 31A, and the second rotation speed sensor 31B are connected to the input I / F, and the first to fourth solenoid valves 341 to 344, the engine control unit 300, and the TM control unit 320 are connected to the output I / F.

[0100] In such a hardware configuration, the CPU reads out a control program (software) stored in a recording medium such as a ROM, HDD, or optical disk, expands it on the RAM, and executes the expanded control program, whereby the control program and hardware cooperate to realize the functions of the controller 5 .

[0101] In addition, in this embodiment, the controller 5 is described as a computer composed of a combination of software and hardware, but the present invention is not limited to this. For example, as an example of another computer structure, an integrated circuit that realizes the functions of the control program executed on the wheel loader 1 side may be used.

[0102] like Figure 5 As shown, the controller 5 includes a data acquisition unit 51 , a mode determination unit 52 , a mining determination unit 53 , a priority control unit 54 , a control unit 55 , and a storage unit 56 .

[0103] The data acquisition unit 51 respectively acquires data related to the mode signal output from the third mode selection switch 63, the input shaft rotation speed RS1 output from the first rotation speed sensor 31A, the output shaft rotation speed RS2 output from the second rotation speed sensor 31B, the discharge pressure Pa output from the discharge pressure sensor 33A, and the vehicle speed S output from the vehicle speed sensor 15A.

[0104] The mode determination unit 52 determines whether the semi-automatic excavation mode is on based on the mode signal acquired by the data acquisition unit 51. Specifically, the mode determination unit 52 determines that the semi-automatic excavation mode is on when the mode signal acquired by the data acquisition unit 51 is a mode signal related to the heavy excavation mode or the light excavation mode. On the other hand, the mode determination unit 52 determines that the semi-automatic excavation mode is off when the mode signal acquired by the data acquisition unit 51 is a mode signal related to mode off.

[0105] In the present embodiment, the mode determination unit 52 determines which mode, the heavy excavation mode or the light excavation mode, is selected by the third mode selection switch 63 based on the mode signal acquired by the data acquisition unit 51 .

[0106] The excavation determination unit 53 determines whether the excavation operation has started based on the input shaft rotation speed RS1, the output shaft rotation speed RS2, and the discharge pressure Pa acquired by the data acquisition unit 51. Here, the start of the excavation operation refers to the case where the torque converter speed ratio (RS1 / RS2) is less than a predetermined threshold value RSth and the discharge pressure Pa is greater than a predetermined pressure threshold value Pth (RS1 / RS2<RSth and Pa>Pth).

[0107] The predetermined threshold value RSth is a threshold value related to the travel drive when judging the start of excavation, and is a value set based on the maximum torque converter speed ratio that can be excavated. The predetermined pressure threshold value Pth is a threshold value related to the operation of the cargo handling operation device 2 when judging the start of excavation, and is a value set based on the minimum discharge pressure of the hydraulic pump 33 required for excavation. Both the predetermined threshold value RSth and the predetermined pressure threshold value Pth can be arbitrarily set and changed.

[0108] In addition, in the present embodiment, the discharge pressure of the hydraulic pump 33 is used for judging the start of excavation, but the present invention is not limited thereto, and the cylinder bottom pressure of the lift arm hydraulic cylinder 22 may be used. The start of excavation in this case refers to the case where the torque converter speed ratio (RS1 / RS2) is less than a predetermined threshold value RSth and the cylinder bottom pressure Pb is greater than a predetermined pressure threshold value Pbth (RS1 / RS2<RSth and Pb>Pbth).

[0109] In addition, the excavation determination unit 53 determines whether the excavation operation is completed based on the vehicle speed S acquired by the data acquisition unit 51. Here, the excavation operation is completed when the vehicle speed S is greater than a predetermined speed threshold Sth (S>Sth). The predetermined speed threshold Sth is a value set based on the minimum vehicle speed required when the wheel loader 1 performs the transport operation, and can be arbitrarily set and changed.

[0110] In addition, in the present embodiment, the vehicle speed is used to determine the end of excavation, but the present invention is not limited thereto, and the position of the bucket 23 and the operation of the cargo handling device 2 may also be used. Specifically, as the condition for the end of excavation, the bucket 23 may be moved to the maximum tilt position or the cargo handling device 2 may be operated.

[0111] When the mode judgment unit 52 judges that it is the semi-automatic excavation mode and the excavation judgment unit 53 judges that the excavation operation has started, that is, when the semi-automatic excavation mode is selected by the third mode selection switch 63, and the excavation operation has started and is in the excavation operation based on the semi-automatic excavation mode, the priority control unit 54 makes the control based on the semi-automatic excavation mode take priority over the control based on the driving mode and the control based on the working mode, and sets the switch from the semi-automatic excavation mode to the normal mode (driving mode and working mode) to be invalid.

[0112] Furthermore, the "control based on the semi-automatic excavation mode" in the controller 5 means automatically controlling the operation of the cargo handling operation device 2, and controlling the rotation speed of the engine 30 and the speed level of the transmission 32 according to the specific gravity and water content of the operation object. That is, the "control based on the semi-automatic excavation mode" in this embodiment means control based on the heavy excavation mode or the light excavation mode in the semi-automatic excavation mode.

[0113] Therefore, in the controller 5 , when the control based on the semi-automatic excavation mode is prioritized, even if the data acquisition unit 51 acquires the mode signal from the first mode selection switch 61 and the second mode selection switch 62 , the control based on the travel mode and the control based on the work mode are not performed.

[0114] In addition, when the excavation judgment unit 53 determines that the excavation work is completed while the control based on the semi-automatic excavation mode is prioritized, the priority control unit 54 cancels the priority of the control based on the semi-automatic excavation mode and enables the switch from the semi-automatic excavation mode to the normal mode (travel mode and work mode).

[0115] Therefore, in the controller 5 , after the priority of the control based on the semi-automatic excavation mode is released, when the data acquisition unit 51 acquires the mode signal from the first mode selection switch 61 and the second mode selection switch 62 , the control based on the travel mode and the control based on the work mode are executed.

[0116] The control unit 55 includes a cargo handling control unit 551 and a traction control unit 552 .

[0117] When the heavy excavation mode is selected in the third mode selection switch 63, the cargo handling control unit 551 outputs a command signal related to the heavy excavation mode to the first to fourth solenoid valves 341 to 344. As a result, the cargo handling operation device 2 automatically performs an action corresponding to the heavy excavation without relying on the operation of the operating levers 121 and 122 by the operator. The action corresponding to the heavy excavation is, for example, an action of tilting the bucket 23 at a small angle (tilt amount) and a high frequency and a small stroke, and slowly lifting the lift arm 21.

[0118] In addition, when the light excavation mode is selected in the third mode selection switch 63, the cargo handling control unit 551 outputs a command signal related to the light excavation mode to the first to fourth solenoid valves 341 to 344. As a result, the cargo handling operation device 2 automatically performs an action corresponding to the light excavation without relying on the operation of the operating levers 121 and 122 by the operator. The action corresponding to the light excavation is, for example, an action of tilting the bucket 23 at a large angle (tilt amount) and a low frequency and an action of lifting the lift arm 21 quickly.

[0119] Furthermore, in the control based on the semi-automatic excavation mode, the control of the cargo handling work machine 2 may be the same in both the heavy excavation mode and the light excavation mode.

[0120] When the heavy excavation mode is selected by the third mode selection switch 63, the traction control unit 552 outputs a command signal related to the heavy excavation mode (first automatic mode + P mode) to the engine control unit 300 and the TM control unit 320. As a result, the engine 30 is in a state where the speed limit is turned off, and the transmission 32 automatically reduces the speed stage to the first speed stage.

[0121] Furthermore, when the light excavation mode is selected by the third mode selection switch 63, the traction control unit 552 outputs a command signal related to the light excavation mode (second automatic mode + STD mode) to the engine control unit 300 and the TM control unit 320. As a result, the engine 30 limits the rotation speed, and the transmission 32 reduces the speed stage to only the second speed stage.

[0122] That is, in the present embodiment, the controller 5 switches between the heavy excavation mode and the light excavation mode based on the third mode selection switch 63 .

[0123] The storage unit 56 is a memory, and stores therein a predetermined threshold value RSth, a predetermined pressure threshold value Pth, and a predetermined speed threshold value Sth.

[0124] (Control based on semi-automatic excavation mode)

[0125] Next, refer to Figure 6 The flow of the process based on the control in the semi-automatic excavation mode executed in the controller 5 will be described.

[0126] Figure 6 This is a flowchart showing the flow of a process based on control in the semi-automatic excavation mode executed by the controller 5 in the first embodiment.

[0127] First, the data acquisition unit 51 acquires the mode signal output from the third mode selection switch 63 (step S501). Then, the mode determination unit 52 determines whether it is the semi-automatic excavation mode, that is, whether the semi-automatic excavation mode is on, based on the mode signal acquired in step S501 (step S502).

[0128] When it is determined in step S502 that the mode is the semi-automatic excavation mode (step S502 / yes), the data acquisition unit 51 respectively acquires the input shaft rotation speed RS1 detected by the first rotation speed sensor 31A, the output shaft rotation speed RS2 detected by the second rotation speed sensor 31B, and the discharge pressure Pa detected by the discharge pressure sensor 33A (step S503).

[0129] Next, the excavation determination unit 53 determines whether the wheel loader 1 has started the excavation work based on the input shaft rotation speed RS1, the output shaft rotation speed RS2, and the discharge pressure Pa acquired in step S503 (step S504).

[0130] When it is determined in step S504 that the excavation work has started (step S504 / Yes), the priority control unit 54 prioritizes the control based on the semi-automatic excavation mode (step S505 ).

[0131] Next, the mode determination unit 52 determines whether or not the heavy excavation mode or the light excavation mode is selected by the third mode selection switch 63 based on the mode signal acquired in step S501 (step S506 ).

[0132] When it is determined in step S506 that the heavy excavation mode is selected (step S506 / heavy excavation), the control unit 55 outputs a command signal related to the heavy excavation mode to each of the first to fourth solenoid valves 341 to 344 , the engine control unit 300 , and the TM control unit 320 (step S507 ).

[0133] Next, the data acquisition unit 51 acquires the vehicle speed S detected by the vehicle speed sensor 15A (step S508 ). Then, the excavation determination unit 53 determines whether the wheel loader 1 has completed the excavation work based on the vehicle speed S acquired in step S508 (step S509 ).

[0134] When it is determined in step S509 that the excavation work is completed (step S509 / Yes), the priority control unit 54 releases the priority of the control based on the semi-automatic excavation mode executed in step S505 (step S510), and the processing of the control based on the semi-automatic excavation mode in the controller 5 ends.

[0135] On the other hand, when it is determined in step S509 that the excavation work is continuing (step S509 / No), the process returns to step S507 and repeats the process.

[0136] When it is determined in step S506 that the light excavation mode is selected (step S506 / light excavation), the control unit 55 outputs command signals related to the light excavation mode to the first to fourth solenoid valves 341 to 344, the engine control unit 300, and the TM control unit 320 (step S511).

[0137] Next, similarly to step S508, the data acquisition unit 51 acquires the vehicle speed S detected by the vehicle speed sensor 15A (step S512). Then, the excavation determination unit 53 determines whether the wheel loader 1 has completed the excavation work based on the vehicle speed S acquired in step S512 (step S513).

[0138] When it is determined in step S513 that the excavation work is completed (step S513 / Yes), the process proceeds to step S510 , and the control process based on the semi-automatic excavation mode in the controller 5 ends.

[0139] On the other hand, when it is determined in step S513 that the excavation work is continuing (step S513 / No), the process returns to step S511 and repeats the process.

[0140] In addition, in any of the cases where it is determined in step S502 that it is not the semi-automatic excavation mode, that is, the semi-automatic excavation mode is turned off (step S502 / No), and in step S504 it is determined that the excavation work has not started (step S504 / No), the control processing based on the semi-automatic excavation mode in the controller 5 is completed.

[0141] In this way, when the controller 5 selects the semi-automatic excavation mode in the third mode selection switch 63, and excavation starts and is in the excavation operation based on the semi-automatic excavation mode, the speed of the engine 30 and the speed level of the transmission 32 are automatically adjusted in accordance with the set mode (heavy excavation mode or light excavation mode) based on the specific gravity and water content of the work object.

[0142] Specifically, when the heavy excavation mode is set, the traction force of the wheel loader 1 is greater than that in the light excavation mode. In other words, when the light excavation mode is set, the traction force of the wheel loader 1 is smaller than that in the heavy excavation mode.

[0143] Thus, when the wheel loader 1 performs semi-automatic excavation, it is possible to maintain a good balance between the traction force and the digging force of the cargo handling device 2 according to the specific gravity (type) and water content of the work object, thereby achieving improved efficiency of the excavation work.

[0144] In addition, in the present embodiment, when the semi-automatic excavation mode is selected and the excavation operation starts and is in the process of excavation operation based on the semi-automatic excavation mode, the controller 5 gives priority to control based on the semi-automatic excavation mode. Thus, even when the first mode selection switch 61 and the second mode selection switch 62 are operated, it is possible to prevent the engine 30 and the transmission 32 from suddenly moving according to the driving mode and the working mode.

[0145] <Second embodiment>

[0146] Next, refer to Figure 7 as well as Figure 8 A second embodiment of the present invention will be described. Figure 7 as well as Figure 8In the description, the same reference numerals are given to the components common to the components of the wheel loader 1 described in the first embodiment, and the description thereof will be omitted. The same treatment is also applied to the third embodiment.

[0147] Figure 7 This is a functional block diagram showing the functions of the controller 5A in the second embodiment. Figure 8 This is a flowchart showing the flow of a process based on control in the semi-automatic excavation mode executed by the controller 5A in the second embodiment.

[0148] In this embodiment, the third mode selection switch 63A only selects the on / off of the semi-automatic excavation mode, and the controller 5A selects the heavy excavation mode and the light excavation mode. Therefore, the mode signal output from the third mode selection switch 63A is a signal related to the on / off of the semi-automatic excavation mode.

[0149] like Figure 7 As shown, the controller 5A includes a mode selection unit 57 in addition to the data acquisition unit 51, the mode determination unit 52A, the excavation determination unit 53, the priority control unit 54, the control unit 55A (the cargo handling control unit 551 and the traction control unit 552), and the storage unit 56A.

[0150] The mode selection unit 57 selects a setting mode that is optimal for the work object from the heavy excavation mode and the light excavation mode (switches the heavy excavation mode and the light excavation mode) based on the discharge pressure Pa used for judging the start of the excavation work in the excavation judging unit 53, that is, the discharge pressure Pa of the hydraulic pump 33 immediately before the start of the excavation. Specifically, the mode selection unit 57 judges whether the discharge pressure Pa is greater than a predetermined pressure threshold value Pth2.

[0151] The predetermined pressure threshold value Pth2 is a value set based on the relief pressure of the hydraulic pump 33, and is, for example, a pressure of 80 to 90% of the relief pressure. The predetermined pressure threshold value Pth2 can be arbitrarily set and changed, and is stored in the storage unit 56A.

[0152] The mode selection unit 57 selects the heavy excavation mode when the discharge pressure Pa is greater than a predetermined pressure threshold value Pth2 (Pa>Pth2). On the other hand, the mode selection unit 57 selects the light excavation mode when the discharge pressure Pa is determined to be less than the predetermined pressure threshold value Pth2 (Pa≤Pth2).

[0153] Therefore, in the present embodiment, the mode determination unit 52A determines only whether the semi-automatic excavation mode is valid or invalid based on the mode signal acquired by the data acquisition unit 51 .

[0154] When the mode determination unit 52A determines that the semi-automatic excavation mode is in progress and the excavation determination unit 53 determines that the excavation work has started, the control unit 55A executes processing based on the setting mode (heavy excavation mode or light excavation mode) selected by the mode selection unit 57 .

[0155] like Figure 8 As shown, if the control based on the semi-automatic excavation mode is prioritized in step S505, the mode selection unit 57 determines whether the discharge pressure Pa acquired in step S503 is greater than a predetermined pressure threshold value Pth2 (step S506A).

[0156] When it is determined in step S506A that the discharge pressure Pa is greater than the predetermined pressure threshold value Pth2 (Pa>Pth2) (step S506A / Yes), the mode selection unit 57 selects the heavy excavation mode. Then, the control unit 55A outputs a command signal related to the heavy excavation mode to the first to fourth solenoid valves 341 to 344, the engine control unit 300, and the TM control unit 320 (step S507A), and the process proceeds to step S508.

[0157] On the other hand, when it is determined in step S506A that the discharge pressure Pa is less than or equal to the predetermined pressure threshold value Pth2 (Pa≤Pth2) (step S506A / No), the mode selection unit 57 selects the light excavation mode. Then, the control unit 55A outputs a command signal related to the light excavation mode to each of the first to fourth solenoid valves 341 to 344, the engine control unit 300, and the TM control unit 320 (step S511A), and the process proceeds to step S512.

[0158] In this embodiment as well, the same operations and effects as those in the first embodiment can be achieved.

[0159] <Third embodiment>

[0160] Next, refer to Fig. 9 as well as Fig.10 A third embodiment of the present invention will be described.

[0161] Fig. 9 This is a functional block diagram showing the functions of the controller 5B in the third embodiment. Fig.10 This is a flowchart showing the flow of a process based on control in the semi-automatic excavation mode executed by the controller 5B in the third embodiment.

[0162] The controller 5B of this embodiment is similar to the controller 5A of the second embodiment, and further includes a mode selection unit 57B in addition to the data acquisition unit 51B, the mode determination unit 52A, the excavation determination unit 53, the priority control unit 54, the control unit 55A (the cargo handling control unit 551 and the traction control unit 552), and the storage unit 56B.

[0163] However, the mode selection unit 57B is different from the mode selection unit 57 in the second embodiment, and selects the setting mode that is optimal for the work object from the heavy excavation mode and the light excavation mode based on the load W of the cargo (work object) in the bucket 23. Specifically, the mode selection unit 57B determines whether the load W of the cargo in the bucket 23 after the excavation is completed is greater than a predetermined load threshold value Wth. In addition, the load W of the cargo in the bucket 23 is measured by the load sensor 23A in the state where the lift arm 21 is raised after the excavation is completed.

[0164] The predetermined load threshold value Wth is a value set based on the rated load of each vehicle specification, and is, for example, a weight of 80 to 90% of the rated load. The predetermined load threshold value Wth can be arbitrarily set and changed, and is stored in the storage unit 56B.

[0165] When the mode selection unit 57B determines that the load W measured by the load sensor 23A is greater than the predetermined load threshold value Wth (W>Wth), the heavy excavation mode is selected as the next setting mode. On the other hand, when the mode selection unit 57B determines that the load W measured by the load sensor 23A is less than the predetermined load threshold value Wth (W≤Wth), the light excavation mode is selected as the next setting mode. The next setting mode selected by the mode selection unit 57B is stored in the storage unit 56B.

[0166] In addition, the mode selection unit 57B selects the heavy excavation mode as the first setting mode. That is, the controller 5B stores the default setting mode as the heavy excavation mode in the storage unit 56B.

[0167] In addition, "first time" means when the power of the controller 5B is turned on and the control based on the semi-automatic excavation mode is performed for the first time since the start-up. Therefore, the "first time" does not include the case where the semi-automatic excavation mode is turned off and then turned on again in the state where the controller 5B is started (the power is turned on continuously).

[0168] like Fig.10 As shown, if the control based on the semi-automatic excavation mode is prioritized in step S505, the controller 5B determines whether the control based on the semi-automatic excavation mode is the first time (step S521).

[0169] When it is determined in step S521 that it is the first control based on the semi-automatic excavation mode (step S521 / Yes), the mode selection unit 57B selects the heavy excavation mode. Then, the control unit 55A outputs a command signal related to the heavy excavation mode to the first to fourth solenoid valves 341 to 344, the engine control unit 300, and the TM control unit 320 (step S507B), and the process proceeds to step S508.

[0170] On the other hand, when it is determined in step S521 that this is not the first control based on the semi-automatic excavation mode, that is, it is the control based on the semi-automatic excavation mode after the second time (step S521 / No), the controller 5B determines whether the "next setting mode" stored in the storage unit 56B is any one of the setting modes of the heavy excavation mode and the light excavation mode (step S526).

[0171] When it is determined in step S526 that the stored “next setting mode” is the heavy digging mode (step S526 / heavy digging), the process proceeds to step S507B.

[0172] On the other hand, when it is determined in step S526 that the stored "next setting mode" is the light excavation mode (step S526 / light excavation), the mode selection unit 57B selects the light excavation mode. Then, the control unit 55A outputs a command signal related to the light excavation mode to the first to fourth solenoid valves 341 to 344, the engine control unit 300, and the TM control unit 320 (step S511B), and the process proceeds to step S512.

[0173] Then, when it is determined in step S509 and step S513 that the excavation end condition is satisfied (step S509 / Yes, step S513 / Yes), the data acquisition unit 51B acquires the load W measured by the load sensor 23A (step S522).

[0174] Next, the mode selection unit 57B determines whether the load W acquired in step S522 is larger than a predetermined load threshold value Wth (step S523 ).

[0175] When it is determined in step S523 that the load W is greater than the predetermined load threshold value Wth (W>Wth) (step S523 / Yes), the mode selection unit 57B selects the heavy excavation mode as the next setting mode and outputs it to the storage unit 56B (step S524). Thus, the storage unit 56B stores information indicating that the next setting mode is the heavy excavation mode.

[0176] On the other hand, when it is determined in step S523 that the load W is less than or equal to the predetermined load threshold value Wth (W≤Wth) (step S523 / No), the mode selection unit 57B selects the light excavation mode as the next setting mode and outputs it to the storage unit 56B (step S525). Thus, the storage unit 56B stores information indicating that the next setting mode is the light excavation mode.

[0177] After the next setting mode is selected and stored in the storage unit 56B in steps S524 and S525 , the priority control unit 54 cancels the priority of the control based on the semi-automatic excavation mode (step S510B), and the processing in the controller 5B ends.

[0178] In addition, in the present embodiment, after the data acquisition unit 51B acquires the data related to the load W output from the load sensor 23A (step S522), the mode selection unit 57B compares the load W with the specified load threshold Wth and selects the next setting mode, but is not limited to this. The load W acquired by step S522 may be stored, and during the next excavation, that is, in step S526, the stored load W is compared with the specified load threshold Wth to select the setting mode.

[0179] In this embodiment as well, the same operations and effects as those in the first embodiment can be achieved.

[0180] The above describes the various embodiments of the present invention. In addition, the present invention is not limited to the various embodiments described above, and includes various modifications. For example, the various embodiments described above are described in detail to facilitate understanding of the present invention, and are not limited to having all the described structures. In addition, a part of the structure of each embodiment can be replaced with the structure of other embodiments, and the structure of other embodiments can also be added to the structure of each embodiment. In addition, other structures can be added, deleted, or replaced with a part of the structure of each embodiment.

[0181] For example, in each of the above-mentioned embodiments, the wheel loader 1 is equipped with two modes, namely, a travel mode and an operation mode, as normal modes. However, the normal mode does not necessarily have two modes. As long as the control of the action of the cargo loading and unloading operation device 2 is based on the control of the operation amount of the operating levers 121 and 122, there is no particular restriction on the control content of the travel drive device 3.

[0182] Furthermore, in each of the above-described embodiments, the travel drive device 3 is of a torque converter type, but the present invention is not limited thereto and may be, for example, an HST (Hydraulic Static Transmission) type or the like.

[0183] In addition, in each of the above-mentioned embodiments, the controllers 5, 5A, and 5B set the speed level of the transmission 32 to the first speed level as the lowest speed level in the heavy excavation mode, and set the speed level of the transmission 32 to be greater than the first speed level in the light excavation mode, but are not limited to this. At least, the control may be performed in such a manner that the speed of the engine 30 is not limited in the heavy excavation mode, and the speed of the engine 30 is limited in the light excavation mode.

[0184] Description of Reference Numerals

[0185] 1: Wheel loader

[0186] 1A: Front frame (body)

[0187] 1B: Rear frame (body)

[0188] 2: Cargo handling equipment

[0189] 3: Travel drive device

[0190] 5.5A,5B: Controller

[0191] 11, 11A: front wheel (wheel)

[0192] 11, 11B: rear wheel (wheel)

[0193] 30: Engine

[0194] 31: Torque Converter

[0195] 32: Gearbox

[0196] 33: Hydraulic pump

[0197] 43: Accelerator pedal (driving operating device)

[0198] 61-63: 1st to 3rd mode selection switches (mode selection device)

[0199] 121, 122: Operating lever (cargo loading and unloading operating device).

Claims

1. A wheel loader comprising: Car body; an engine mounted on the vehicle body; a travel drive device driven by the engine to cause the vehicle body to travel; A travel operating device for operating the travel drive device; A hydraulically driven cargo handling device installed on the vehicle body and configured to dig out the work object; a hydraulic pump driven by the engine to supply hydraulic oil to a driving portion of the cargo handling operation device; A cargo handling operation device for operating the cargo handling operation device; A controller for respectively controlling the engine, the travel drive device, and the cargo handling operation device; and a mode selection device for selecting a normal mode and a semi-automatic excavation mode, wherein the normal mode is a mode in which the controller controls the cargo handling operation device based on an operation signal output from the cargo handling operation device, and the semi-automatic excavation mode is a mode in which the controller automatically controls the travel drive device and the cargo handling operation device based on an operation signal output from the travel operation device in order to support an operator's operation, The wheel loader is characterized in that: The semi-automatic mining mode has: a first excavation mode in which the controller does not limit the rotation speed of the engine; and a second excavation mode in which the controller limits the rotation speed of the engine so that the traction force by the travel drive device becomes smaller than that in the first excavation mode; The controller switches the first excavation mode and the second excavation mode based on a state in which the semi-automatic excavation mode has been selected by the mode selection device, or based on a state in which the semi-automatic excavation mode has been selected by the mode selection device and a discharge pressure of the hydraulic pump immediately before the start of the excavation work.

2. The wheel loader according to claim 1, characterized in that: The mode selection device is an input device capable of selecting the first excavation mode and the second excavation mode, and when either the first excavation mode or the second excavation mode is selected, the semi-automatic excavation mode is selected.

3. The wheel loader according to claim 1, characterized in that: The controller is configured as follows: selecting the first excavation mode when the discharge pressure of the hydraulic pump immediately before the start of the excavation work is greater than a predetermined pressure threshold; The second excavation mode is selected when the discharge pressure of the hydraulic pump immediately before the start of the excavation work is equal to or lower than the predetermined pressure threshold.

4. The wheel loader according to claim 1, characterized in that: The travel drive device comprises: a torque converter that amplifies torque transmitted from the engine; and a transmission capable of switching between a plurality of speed stages, changing the speed of the amplified torque output from the torque converter and transmitting it to a plurality of wheels, The controller is configured as follows: In the first excavation mode, the speed level of the transmission is set to the first speed level, which is the lowest speed level, and the rotation speed of the engine is not limited. In the second excavation mode, the speed stage of the transmission is set higher than the first speed stage, and the rotation speed of the engine is limited.

5. The wheel loader according to claim 1, wherein: The controller is configured as follows: When the semi-automatic excavation mode has been selected by the mode selection device and the excavation work has started and is being performed in the semi-automatic excavation mode, the switching from the semi-automatic excavation mode to the normal mode is disabled; When the excavation work is completed, switching from the semi-automatic excavation mode to the normal mode is enabled.

Images