WORK VEHICLE AND METHOD FOR CONTROLLING WORK VEHICLE

Abstract

A work vehicle includes a vehicular body, a work implement, and a controller. The work implement has a boom pivotable with respect to the vehicular body, a dipper stick pivotable with respect to the boom, and a bucket pivotable with respect to the dipper stick. The controller calculates a direction of a cutting edge of the bucket and determines a direction in which the cutting edge travels to the side of an open side of the bucket such that the calculated direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle, and the controller thus causes an operation of the work implement to be performed in the direction in which the cutting edge travels.

Description

TECHNICAL FIELD

The present invention relates to a work vehicle.

BACKGROUND ART

A work vehicle such as a hydraulic excavator comprises a work implement having a boom, a dipper stick, and a bucket. When the hydraulic excavator starts an excavating operation, the dipper stick is manipulated to cause the bucket to penetrate soil. As the bucket continues to operate, the bucket penetrates soil deeply and the soil's resistance increases, and accordingly, the boom is manipulated to add an operation to raise the bucket upward to make the bucket's excavation depth appropriate. Furthermore, the dipper stick and the bucket are manipulated and once sufficient soil is introduced into the bucket, the bucket is manipulated to lift up the soil, and furthermore, the boom is manipulated to raise the bucket upward.

For a hydraulic excavator's excavating operation, it is necessary to move manipulation levers of three-axes for the boom, the dipper stick, and the bucket, respectively, to manipulate the movement of the bucket, and it is thus not easy to perform the excavating operation efficiently and requires skill.

In this respect, for example, Japanese Patent Laying-Open No. 61-225429 discloses a method of correcting a bucket in posture by detecting a collision of a back surface of the bucket against an excavation surface in order to reduce an excavation load.

Furthermore, Japanese Patent Laying-Open No. 62-189222 discloses a method of adjusting a bucket's excavation depth by measuring the weight of the soil in the bucket.

CITATION LIST

Patent Literature

PTL 1: Japanese Patent Laying-Open No. 61-225429

PTL 2: Japanese Patent Laying-Open No. 62-189222

SUMMARY OF INVENTION

Technical Problem

However, the excavating operation in the above-mentioned publication requires various calculations and has a possibility of complicated control.

The present invention has been made in view of the above issue, and an object of the present invention is to provide a work vehicle which allows a work implement to operate efficiently in a simple manner, and a method for controlling the work vehicle.

Solution to Problem

A work vehicle according to one aspect of the present invention comprises a vehicular body, a work implement, and a controller. The work implement has a boom pivotable with respect to the vehicular body, a dipper stick pivotable with respect to the boom, and a bucket pivotable with respect to the dipper stick. The controller calculates a direction of a cutting edge of the bucket and determines a direction in which the cutting edge travels to the side of an open side of the bucket such that the calculated direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle, and the controller causes an operation of the work implement to be performed in the direction in which the cutting edge travels.

Preferably, the controller determines the direction in which the cutting edge travels to the side on the open side of the bucket such that the calculated direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form the excavation angle of the predetermined angle for a predetermined period of time, and the controller causes the operation of the work implement to be performed in the direction in which the cutting edge travels.

Preferably, the work vehicle further comprises first and second manipulation levers. The first manipulation lever is operated to output a first manipulation command to the controller to adjust an amount of pivoting the bucket with respect to the dipper stick. The second manipulation lever is operated to output a second manipulation command to the controller to adjust an amount of moving the bucket for the direction in which the cutting edge travels from the direction of the cutting edge to the side on the open side of the bucket.

Preferably, the controller determines whether to cause the operation of the work implement to be performed. When the controller determines that the operation of the work implement is caused to be performed, the controller accepts first and second manipulation commands from the first and second manipulation levers.

Preferably, the controller determines whether to cause the operation of the work implement to be performed in accordance with a manipulation instruction of an operator.

Preferably, the work vehicle further comprises a load detector. The load detector detects a load imposed on the work implement. The controller determines whether to cause the operation of the work implement to be performed according to a result of detection by the load detector.

According to one aspect of the present invention, a method for controlling a work vehicle is a method for controlling a work vehicle including a work implement having a boom pivotable with respect to a vehicular body, a dipper stick pivotable with respect to the boom, and a bucket pivotable with respect to the dipper stick, comprising: calculating a direction of a cutting edge of the bucket; and causing an operation of the work implement to be performed such that the direction of the cutting edge of the bucket as calculated and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle.

Advantageous Effects of Invention

The present work vehicle allows a work implement to operate efficiently in a simple manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of one example of a work vehicle according to an embodiment.

FIG. 2 schematically illustrates a work vehicle CM according to an embodiment.

FIG. 3 is a functional block diagram representing a configuration of a control system 200 to control work vehicle CM according to an embodiment.

FIG. 4 represents a relationship between an excavation angle of a bucket 8 and resistance of soil according to an embodiment.

FIG. 5 is a flowchart of a process of an operation of an excavation work of work vehicle CM according to an embodiment.

FIG. 6 is a functional block diagram representing a configuration of a control system 200# based on a first modification of an embodiment.

FIG. 7 represents an idea of a work vehicle system based on another embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the drawings, although the present invention is not limited thereto. Any constituent element of each embodiment described below can be combined as appropriate. Some constituent element may not be used.

[General Configuration of Work Vehicle]

FIG. 1 is a perspective view of one example of a work vehicle according to an embodiment.

As shown in FIG. 1, in the present example, a work vehicle will be described by referring as an example to a hydraulic excavator CM including a hydraulically actuated work implement 2 as a work implement.

Hydraulic excavator CM includes a vehicular body 1 and work implement 2.

Vehicular body 1 has a revolving unit 3, an operator's cab 4, and a travelling unit 5.

Revolving unit 3 is disposed on a travelling unit 5. Travelling unit 5 supports revolving unit 3. Revolving unit 3 can revolve about an axis AX. An operator's seat 4S on which an operator is seated is provided in operator's cab 4. The operator manipulates hydraulic excavator CM in operator's cab 4. Travelling unit 5 has a pair of crawler belts 5Cr. Hydraulic excavator CM travels as crawler belts 5Cr rotate. Note that travelling unit 5 may be composed of vehicular wheels (or tires).

In the present embodiment, a positional relationship of each part will be described with reference to an operator seated on operator's seat 4S in the cab.

A frontward/rearward direction is a frontward/rearward direction with reference to the operator seated on operator's seat 4S. A rightward/leftward direction is a rightward/leftward direction with respect to the operator seated on operator's seat 4S. The rightward/leftward direction matches the vehicle's widthwise direction (a vehicular widthwise direction). When the operator is seated on operator's seat 4S and faces frontward, the operator faces in the frontward direction, and a direction opposite to the frontward direction is the rearward direction. When the operator is seated on operator's seat 4S and faces frontward, a direction on a right side of the operator is referred to as the rightward direction, and a direction on a left side of the operator is referred to as the leftward direction. The frontward/rearward direction is a direction along the x axis and the rightward/leftward direction is a direction along the y axis. When the operator is seated on operator's seat 4S and faces frontward, the operator faces in the frontward direction (or a +x direction), and a direction opposite to the frontward direction is the rearward direction (or a −x direction). When the operator is seated on operator's seat 4S and faces frontward, a direction on one side of the operator in the vehicular widthwise direction is the right direction (or a +z direction), and a direction on the other side of the operator in the vehicular widthwise direction is the left direction (or a −z direction).

Revolving unit 3 has an engine compartment 9 in which an engine is housed, and a counter weight provided at a rear portion of revolving unit 3. Revolving unit 3 is provided with a handrail 19 in front of engine compartment 9. The engine, a hydraulic pump, etc. are disposed in engine compartment 9.

Work implement 2 is connected to revolving unit 3.

Work implement 2 has a boom 6, a dipper stick 7, a bucket 8, a boom cylinder 10, a dipper stick cylinder 11, and a bucket cylinder 12.

Boom 6 is connected to revolving unit 3 via a boom pin 13. Dipper stick 7 is connected to boom 6 via a dipper stick pin 14. Bucket 8 is connected to dipper stick 7 via a bucket pin 15. Boom cylinder 10 drives boom 6. Dipper stick cylinder 11 drives dipper stick 7. Bucket cylinder 12 drives bucket 8. Boom 6 has a proximal end (or a boom foot) connected to revolving unit 3. Boom 6 has a distal end (or a boom top) connected to a proximal end of dipper stick 7. Dipper stick 7 has a distal end (or a dipper stick top) connected to a proximal end of bucket 8. Boom cylinder 10, dipper stick cylinder 11, and bucket cylinder 12 are all a hydraulic cylinder driven with hydraulic oil.

Boom 6 is pivotable with respect to revolving unit 3 about boom pin 13 serving as a pivot. Dipper stick 7 is pivotable with respect to boom 6 about dipper stick pin 14 serving as a pivot parallel to boom pin 13. Bucket 8 is pivotable with respect to dipper stick 7 about bucket pin 15 serving as a pivot parallel to boom pin 13 and dipper stick pin 14.

Boom pin 13, dipper stick pin 14, and bucket pin 15 are all parallel to the z axis. Boom 6, dipper stick 7, and bucket 8 are all pivotable about an axis parallel to the z axis.

FIG. 2 schematically illustrates work vehicle CM according to an embodiment.

As shown in FIG. 2, work vehicle CM is provided with a boom cylinder stroke sensor 16, a dipper stick cylinder stroke sensor 17, and a bucket cylinder stroke sensor 18.

Boom cylinder stroke sensor 16 is disposed on boom cylinder 10 and senses a length of a stroke of boom cylinder 10 (a boom cylinder length). Dipper stick cylinder stroke sensor 17 is disposed on dipper stick cylinder 11 and senses a length of a stroke of dipper stick cylinder 11 (a dipper stick cylinder length). Bucket cylinder stroke sensor 18 is disposed on bucket cylinder 12 and senses a length of a stroke of bucket cylinder 12 (bucket cylinder length).

In the following description, a length of a stroke of boom cylinder 10 will also be referred to as a boom cylinder length or a boom stroke. A length of a stroke of a dipper stick cylinder 11 will also be referred to as a dipper stick cylinder length or a dipper stick stroke. A length of a stroke of bucket cylinder 12 will also be referred to as a bucket cylinder length or a bucket stroke.

Furthermore, the boom cylinder length, the dipper stick cylinder length and the bucket cylinder length will collectively be also referred to as cylinder length data.

Boom 6 has a length L1, which is a distance between boom pin 13 and dipper stick pin 14. Dipper stick 7 has a length L2, which is a distance between dipper stick pin 14 and bucket pin 15. Bucket 8 has a length L3, which is a distance between bucket pin 15 and a cutting edge 8a of bucket 8. Bucket 8 has a plurality of blades, and in the present example, a tip portion of bucket 8 will be referred to as cutting edge 8a. Note that bucket 8 may have no blade. The tip portion of bucket 8 may be formed of a steel plate having a straight shape.

In the present example, an x- and y-axis vehicular body coordinate system with boom pin 13 as a reference point (or a reference position) is shown.

An inclination angle θ1 of boom 6 with respect to a horizontal direction in the vehicular body coordinate system is calculated from cylinder length data sensed by boom cylinder stroke sensor 16.

An inclination angle θ2 of dipper stick 7 with respect to boom 6 is calculated from cylinder length data sensed by dipper stick cylinder stroke sensor 17.

An inclination angle θ3 of cutting edge 8a of bucket 8 with respect to dipper stick 7 is calculated from cylinder length data sensed by bucket cylinder stroke sensor 18.

Based on lengths L1 to L3 and inclination angles θ1 to θ3 of boom 6, dipper stick 7 and bucket 8, a position of cutting edge 8a of bucket 8 and an angle of cutting edge 8a of bucket 8 (the cutting edge's direction) in the x- and y-axis vehicular body coordinate system can be calculated.

In the present example, positional coordinates [x1, y1] of cutting edge 8a of bucket 8 and a cutting edge angle [a] of cutting edge 8a of bucket 8 with respect to the horizontal direction are shown.

While in the present example a method of sensing a stroke length by using a stroke sensor, and calculating inclination angle θ will be described, the inclination angle may be calculated by using an angle detector such as a rotary encoder.

[Configuration of Hydraulic System]

FIG. 3 is a functional block diagram representing a configuration of a control system 200 to control work vehicle CM according to an embodiment.

As shown in FIG. 3, control system 200 according to the embodiment controls an excavation process using work implement 2.

Control system 200 includes boom cylinder stroke sensor 16, dipper stick cylinder stroke sensor 17, bucket cylinder stroke sensor 18, a manipulation device 25, a work implement controller 26, a hydraulic cylinder 60, a directional control valve 64, and a pressure sensor 66.

Manipulation device 25 is disposed in operator's cab 4. Manipulation device 25 is manipulated by the operator. Manipulation device 25 receives a manipulation command of the operator to drive work implement 2. Manipulation device 25 is a manipulation device of a pilot hydraulic system as an example.

Directional control valve 64 adjusts an amount of hydraulic oil supplied to hydraulic cylinder 60. Directional control valve 64 is actuated by oil supplied. In the present example, oil supplied to a hydraulic cylinder (boom cylinder 10, dipper stick cylinder 11, and bucket cylinder 12) in order to actuate the hydraulic cylinder is also referred to as hydraulic oil. Furthermore, oil supplied to directional control valve 64 to actuate directional control valve 64 is referred to as pilot oil. Furthermore, the pilot oil's pressure is also referred to as pilot oil pressure.

The hydraulic oil and the pilot oil may be pumped from the same hydraulic pump. For example, the hydraulic oil pumped from the hydraulic pump may have a portion reduced in pressure by a reducing valve, and the hydraulic oil reduced in pressure may be used as the pilot oil. Further, a hydraulic pump (a main hydraulic pump) for pumping the hydraulic oil and a hydraulic pump (a pilot hydraulic pump) for pumping the pilot oil may be different hydraulic pumps.

Further, in the present example, the pilot oil pumped from the main hydraulic pump and reduced in pressure by the reducing valve is supplied to manipulation device 25.

The pilot oil pressure is adjusted based on the amount of manipulating manipulation device 25. Pressure sensor 66 is connected to manipulation device 25. Pressure sensor 66 senses a pilot oil pressure generated in response to manipulation of a lever of manipulation device 25 and outputs it to work implement controller 26.

In response to the pilot oil pressure sensed by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing the hydraulic oil supplied to hydraulic cylinder 60 (boom cylinder 10, dipper stick cylinder 11, and bucket cylinder 12).

Manipulation device 25 includes a first manipulation lever 25R, a second manipulation lever 25L, and an excavation mode setting button 25P. First manipulation lever 25R is disposed, for example, on the right side of driver's seat 4S. Second manipulation lever 25L is disposed, for example, on the left side of operator's seat 4S. For first manipulation lever 25R and second manipulation lever 25L, forward, backward, rightward and leftward operations correspond to operations along two axes.

Excavation mode setting button 25P is a setting button for setting an excavation mode. Work implement controller 26 shifts from a normal mode to the excavation mode in response to an instruction issued as the operator presses excavation mode setting button 25P. Furthermore, work implement controller 26 shifts from the excavation mode to the normal mode in response to an instruction issued as the operator again presses excavation mode setting button 25P.

In the present example, first manipulation lever 25R and second manipulation lever 25L of manipulation device 25 can change a function corresponding to a manipulation between the normal mode and the excavation mode.

In the normal mode, first manipulation lever 25R is manipulated to manipulate boom 6 and bucket 8.

A forward/backward manipulation of first manipulation lever 25R corresponds to a manipulation of boom 6, and in response to the forward/backward manipulation, boom 6 is raised/lowered. The lever is manipulated to manipulate boom 6.

A rightward/leftward manipulation of first manipulation lever 25R corresponds to a manipulation of bucket 8, and in response to the rightward/leftward manipulation, bucket 8 is operated to excavate soil and be released. The lever is manipulated to manipulate bucket 8.

Second manipulation lever 25L is manipulated to manipulate dipper stick 7 and revolving unit 3.

A forward/backward manipulation of second manipulation lever 25L corresponds to a manipulation of dipper stick 7, and in response to the forward/backward manipulation, dipper stick 7 is raised/lowered. The lever is manipulated to manipulate dipper stick 7.

A rightward/leftward manipulation of second manipulation lever 25L corresponds to revolution of revolving unit 3, and in response to the rightward/leftward manipulation, revolving unit 3 revolves rightward and leftward.

In response to an amount of manipulating first manipulation lever 25R in the forward/backward direction (an amount of manipulating the boom), as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to boom cylinder 10 for driving boom 6.

In response to an amount of manipulating first manipulation lever 25R in the rightward and leftward direction (an amount of manipulating the bucket), as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to bucket cylinder 12 for driving bucket 8.

In response to an amount of manipulating second manipulation lever 25L in the forward/backward direction (an amount of manipulating the dipper stick), as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to dipper stick cylinder 11 for driving dipper stick 7.

In response to an amount of manipulating second manipulation lever 25L in the rightward and leftward direction, as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to a hydraulic actuator for driving revolving unit 3.

Note that a rightward/leftward manipulation of first manipulation lever 25R may correspond to a manipulation of boom 6 and a forward/backward manipulation thereof may correspond to that of bucket 8. Note that a rightward/leftward manipulation of second manipulation lever 25L may correspond to a manipulation of dipper stick 7 and a forward/backward manipulation thereof may correspond to that of revolving unit 3.

In the excavation mode, first manipulation lever 25R is manipulated to manipulate bucket 8. A rightward/leftward manipulation of first manipulation lever 25R corresponds to a manipulation of bucket 8, and in response to the rightward/leftward manipulation, bucket 8 is rotated. The forward/backward manipulation of first manipulation lever 25R is disabled. Accordingly, no manipulation of the lever to manipulate boom 6 is accepted.

In the excavation mode, second manipulation lever 25L is manipulated to adjust an amount of moving cutting edge 8a of bucket 8. Forward manipulation of second manipulation lever 25L corresponds to controlling an amount of moving cutting edge 8a of bucket 8. When second manipulation lever 25L is inclined forward in a large amount bucket 8 has cutting edge 8a moved in an increased amount. When second manipulation lever 25L is inclined forward in a small amount bucket 8 has cutting edge 8a moved in a reduced amount.

Manipulation of second manipulation lever 25L in any other direction is disabled. Accordingly, no manipulation of the lever to manipulate dipper stick 7 and revolving unit 3 is accepted.

[Resistance of Soil]

FIG. 4 represents a relationship between an excavation angle of bucket 8 and resistance of soil according to an embodiment.

In the present example, an excavation angle represents an angle between a direction of cutting edge 8a of bucket 8 and a direction in which cutting edge 8a travels when bucket 8 moves. With reference to the direction of cutting edge 8a of bucket 8, when bucket 8 moves and cutting edge 8a travels in a direction to a side on the open side of bucket 8, the angle has a positive value, whereas when the cutting edge travels in the opposite direction, the angle has a negative value.

As shown in FIG. 4, an excavation angle of bucket 8 around 0° is indicated as a limit angle.

When bucket 8 has an excavation angle smaller than the limit angle, bucket 8 has its exterior or back surface pressed against soil, which rapidly increases a value of resistance of soil against bucket 8.

On the other hand, the figure shows that when bucket 8 has an excavation angle of a predetermined angle Q, bucket 8 experiences resistance of soil of a minimum value against it.

It should be noted that the limit angle and the predetermined angle Q are merely examples and can be set to different values depending on the form of bucket 8.

Work vehicle CM according to the present embodiment performs an excavation process at an excavation angle with a small value of resistance of soil to operate a work implement in a simple manner efficiently. Specifically, work vehicle CM performs the excavation process such that the excavation angle is the predetermined angle Q. Note that in the present example, being the predetermined angle Q does not necessarily mean completely matching the predetermined angle Q, and also includes a value approximate to the predetermined angle Q.

[Process of Operation]

FIG. 5 is a flowchart of a process of an operation of an excavation work of work vehicle CM according to an embodiment.

As shown in FIG. 5, work implement controller 26 determines whether the excavation mode is set (step S2). Specifically, work implement controller 26 determines whether a setting instruction via the excavation mode setting button to set the excavation mode in response to a manipulation command of the operator is received.

In step S2, if work implement controller 26 determines that the excavation mode is set, work implement controller 26 calculates cutting edge data (step S4).

Specifically, work implement controller 26 calculates a boom cylinder length, a dipper stick cylinder length, and a bucket cylinder length based on detection results obtained from boom cylinder stroke sensor 16, dipper stick cylinder stroke sensor 17, and bucket cylinder stroke sensor 18. Inclination angle θ1 of boom 6 with respect to the horizontal direction is calculated from the boom cylinder length. Inclination angle θ2 of dipper stick 7 with respect to boom 6 is calculated from the dipper stick cylinder length. Inclination angle θ3 of cutting edge 8a of bucket 8 with respect to dipper stick 7 is calculated from the bucket cylinder length. Thus, cutting edge data [x1, y1, α1] indicating a position of bucket 8 and a direction of cutting edge 8a of bucket 8 (the cutting edge's direction) in the x- and y-axis vehicular body coordinate system is calculated.

Subsequently, work implement controller 26 calculates an excavating direction vector (step S6).

In the present example, the excavating direction vector is calculated such that an excavation angle formed between a direction in which cutting edge 8a of bucket 8 travels with respect to a direction of cutting edge 8a of bucket 8 is the predetermined angle Q. Thus, a direction in which cutting edge 8a of bucket 8 travels to a side on the open side of bucket 8 is determined.

The excavating direction vector in the vehicular body coordinate system of the present example is indicated by unit vectors dx and dy along the x axis and the y axis, which are represented by the following expressions:

dx=−cos(α1+Q)

dy=−sin(α1+Q).

Subsequently, work implement controller 26 accepts an input via a manipulation lever (step S8).

In the present example, manipulation inputs via first manipulation lever 25R and second manipulation lever 25L are accepted.

As has been described above, in the excavation mode, first manipulation lever 25R is manipulated to rotate bucket 8. Second manipulation lever 25L is manipulated to move the bucket for an excavating direction.

Subsequently, work implement controller 26 calculates an amount of pivoting the bucket and an amount of moving the bucket for excavation in accordance with manipulation inputs received via the manipulation levers (step S10).

Specifically, work implement controller 26 calculates the amount of rotating the bucket based on a pressure generated in response to the manipulation input via first manipulation lever 25R and sensed by and output from pressure sensor 66. Furthermore, work implement controller 26 calculates the amount of moving the bucket for excavation based on a pressure generated in response to the manipulation input via second manipulation lever 25L and sensed by and output from pressure sensor 66.

In the present example, the amount of rotating the bucket and the amount of moving the bucket for excavation based on a result of calculation done by work implement controller 26 are represented as Δd and Δe, respectively.

Subsequently, work implement controller 26 calculates target cutting edge data for cutting edge 8a of bucket 8 moving in response to an input via a manipulation lever (step S12).

Specifically, work implement controller 26 calculates target cutting edge data [x2, y2, α2].

x2=x1+Δd×dx

y2=y1+Δd×dy

α2=α1+Δe

The target cutting edge data [x2, y2, α2] can be calculated from the above equations.

Subsequently, work implement controller 26 operates the work implement based on the target cutting edge data (step S14)

Specifically, work implement controller 26 calculates an inclination angle θ1′ of boom 6, an inclination angle θ2′ of dipper stick 7, and an inclination angle θ3′ of bucket 8 in accordance with the target cutting edge data [x2, y2, α2] of cutting edge 8a of bucket 8 in the x- and y-axis vehicular body coordinate system. Work implement controller 26 calculates a boom cylinder length, a dipper stick cylinder length and a bucket cylinder length based on inclination angles θ1′ to θ3′ of boom 6, dipper stick 7 and bucket 8.

Then, work implement controller 26 drives directional control valve 64 so as to adjust hydraulic oil supplied to hydraulic cylinder 60 so as to achieve the calculated boom, dipper stick and bucket cylinder lengths.

Thus, boom 6, dipper stick 7 and bucket 8 are automatically controlled so that cutting edge 8a of bucket 8 has a position and a direction as indicated by the target cutting edge data.

Subsequently, work implement controller 26 determines whether a work has ended (step S16). When work implement controller 26 determines that the work has ended is for example when the engine is stopped.

In step S16, if work implement controller 26 determines that the work has ended (YES in step S16), work implement controller 26 ends the process (END).

On the other hand, if work implement controller 26 determines in step S16 that the work has not ended (NO in step S16), work implement controller 26 returns to step S2 and repeats the above process.

On the other hand, if work implement controller 26 determines in step S2 that the excavation mode is not set, work implement controller 26 accepts an input via a manipulation lever (step S18).

In the present example, manipulation inputs via first manipulation lever 25R and second manipulation lever 25L are accepted.

As has been previously discussed, in the normal mode, first manipulation lever 25R is manipulated to manipulate boom 6 and bucket 8. Furthermore, second manipulation lever 25L is manipulated to manipulate dipper stick 7 and revolving unit 3.

And work implement controller 26 operates the work implement (step S20).

In response to an amount of manipulating first manipulation lever 25R in the forward/backward direction (an amount of manipulating the boom), as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to boom cylinder 10 for driving boom 6.

In response to an amount of manipulating first manipulation lever 25R in the rightward and leftward direction (an amount of manipulating the bucket), as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to bucket cylinder 12 for driving bucket 8.

In response to an amount of manipulating second manipulation lever 25L in the forward/backward direction (an amount of manipulating the dipper stick), as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to dipper stick cylinder 11 for driving dipper stick 7.

In response to an amount of manipulating second manipulation lever 25L in the rightward and leftward direction, as based on a result of detection by pressure sensor 66, work implement controller 26 drives directional control valve 64 passing hydraulic oil supplied to the hydraulic actuator for driving revolving unit 3.

Subsequently, the control proceeds to step S16.

The process subsequent to the step is similar to that described above, and accordingly, will not be described repeatedly in detail.

In the present example, a direction of cutting edge 8a of bucket 8 is calculated, and an excavating direction vector (a direction in which cutting edge 8a of bucket 8 travels to a side on the open side of bucket 8) is calculated such that an excavation angle formed between the direction in which cutting edge 8a of bucket 8 travels with respect to the direction of cutting edge 8a of bucket 8 is the predetermined angle Q. Automatic control is done to move cutting edge 8a of bucket 8 in accordance with the excavating direction vector, and resistance of soil against bucket 8 is reduced. Reduced resistance (or load) of soil against bucket 8 allows the work implement to operate efficiently in a simple manner.

Further, in the present example, while an excavation mode is set in accordance with an instruction issued as an operator presses excavation mode setting button 25P, the work implement is operated efficiently with a small load as cutting edge 8a of bucket 8 moves in accordance with a predetermined excavating direction vector, and improved fuel economy can be achieved.

Further, in the present example, the excavation mode can be set in response to an instruction issued as an operator presses excavation mode setting button 25P, and the work implement can be operated efficiently with the operator's intention reflected.

Further, in the present example, in the excavation mode, first manipulation lever 25R is manipulated to rotate bucket 8. Further, second manipulation lever 25L is manipulated to move the bucket for an excavating direction. Thus an excavation process is performed in response to manipulation commands via two manipulation levers.

For a conventional hydraulic excavator's excavating operation it is necessary to move manipulation levers of three axes for a boom, a dipper stick, and a bucket, respectively, to manipulate the movement of the bucket, so that it is not easy and requires skill, whereas the present system of the present example allows the movement of the bucket to be manipulated by two manipulation commands so that an efficient excavation process can be performed through a simple manipulation.

First Modification

A work vehicle according to a first modification of the embodiment is not limited to being controlled by an operator's manipulation instruction, and may autonomously control work vehicle CM in the excavation mode.

Specifically, work implement controller 26 determines whether work implement 2 performs an excavation work.

In the first modification will be described a case where whether work implement 2 performs an excavation work is determined depending on a load imposed on work implement 2.

FIG. 6 is a functional block diagram representing a configuration of a control system 200# based on the first modification of an embodiment.

As shown in FIG. 6, control system 200# differs from control system 200 in that a load sensor 28 is further provided. Furthermore, the former differs from the latter in that manipulation device 25 is replaced by a manipulation device 25 #.

Compared to manipulation device 25, manipulation device 25# shows a configuration excluding excavation mode setting button 25P. The remainder in configuration is similar to that described with reference to FIG. 3, and accordingly, it will not be described repeatedly in detail.

In the present example, it is assumed that load sensor 28 is attached to bucket 8 as an example.

Work implement controller 26 determines whether work implement 2 performs an excavation work in accordance with load sensor 28 attached to bucket 8.

When bucket 8 excavates soil, i.e., when bucket 8 is engaged in an excavation work, load sensor 28 indicates an increased value. When bucket 8 does not excavate soil, i.e., when the bucket 8 is not engaged in an excavation work, load sensor 28 indicates a reduced value.

In the present example, work implement controller 26 determines whether a value of a load according to a result of detection from load sensor 28 is a predetermined value or more.

When work implement controller 26 determines that a value of a load according to a result of detection from load sensor 28 is the predetermined value or more, work implement controller 26 determines that the excavation work is performed, and sets the excavation mode.

When work implement controller 26 sets the excavation mode, and first manipulation lever 25R is manipulated, bucket 8 is rotated. Further, when second manipulation lever 25L is manipulated the bucket is moved for an excavating direction. Thus an excavation process is performed in response to two manipulation commands.

On the other hand, when a value of a load according to a result of detection from load sensor 28 is less than the predetermined value, work implement controller 26 does not set the excavation mode. In that case, work implement controller 26 operates in the normal mode.

When work implement controller 26 sets the normal mode, and first manipulation lever 25R is manipulated, boom 6 and bucket 8 are manipulated. Furthermore, when second manipulation lever 25L is manipulated, dipper stick 7 and revolving unit 3 are manipulated.

The work vehicle according to the first modification of the embodiment is of a system to autonomously control work vehicle CM in the excavation mode in accordance with a result of detection from load sensor 28.

This allows the work implement to be operated efficiently in a simple manner.

While in the present embodiment a configuration has been described in which load sensor 28 is attached to bucket 8, it is also possible to adopt a configuration in which a load is sensed by a sensor that measures oil pressure in the hydraulic cylinder. For example, the oil pressure of the hydraulic oil supplied to bucket cylinder 12 may be measured with a sensor to determine a load imposed on bucket 8 in magnitude.

While in the excavation mode, in the above description, a method of manipulating bucket 8 in accordance with manipulation instructions of an operator via first manipulation lever 25R and second manipulation lever 25L in step S8 has been described, this is not exclusive, and bucket 8 may be automatically controlled. More specifically, work implement controller 26 may automatically control bucket 8 by setting an amount of rotating the bucket and an amount of moving the bucket for excavation to a previously programmed and thus set, predetermined value. The predetermined value is not limited to a fixed value. For example, the predetermined value may be changed as time elapses after the excavation mode is started. For example, for a predetermined period of time after the excavation mode is started, i.e., while an excavation process is performed to introduce soil into bucket 8, the predetermined value may be set to a first predetermined value, whereas while the excavation process is performed to scrape soil out of bucket 8, the predetermined value may be set to a second predetermined value.

Other Embodiment

FIG. 7 is a diagram for illustrating an idea of a work vehicle system based on another embodiment.

As shown in FIG. 7, the work vehicle system according to the other embodiment configures a control system to control work vehicle CM from an external base station 300. More specifically, it is a configuration in which a function of work implement controller 26 and manipulation device 25 described in FIG. 3 is provided in external base station 300 or the like.

Base station 300 includes a work implement controller 26# similar in function to work implement controller 26 and a manipulation device 25# similar in function to manipulation device 25.

Work implement controller 26# receives a manipulation command via manipulation device 25# and outputs an operation command for controlling work vehicle CM. Work vehicle CM operates in response to the operation command issued from work implement controller 26#. More specifically, work implement controller 26# outputs an operation command for driving directional control valve 64 described in FIG. 3. Further, work implement controller 26# receives information from boom cylinder stroke sensor 16, dipper stick cylinder stroke sensor 17 and bucket cylinder stroke sensor 18.

This configuration also allows the process for the operation of the excavation work described in the first embodiment with reference to FIG. 5 to be performed by work implement controller 26#.

Thus, even when the work vehicle is controlled from the remote base station 300, the configuration in accordance with the present embodiment can be applied to perform an efficient excavation work.

While in the present embodiment a configuration is described in which an operator controls work vehicle CM in accordance with a manipulation input via a manipulation lever which is a manipulation device, the present invention is also applicable to a configuration in which the manipulation device is not provided and work vehicle CM is autonomously controlled. For example, the present invention can also be applied to a case where a manipulation command to perform an excavation work is preprogrammed and the work implement controller operates in response to the programmed manipulation command. Specifically, it suffices to include a process in which when an autonomous control program for autonomously controlling work vehicle CM is started in accordance with a user's instruction and the work implement controller operates in response to the programmed manipulation command, a direction of the cutting edge of the bucket is calculated and a direction in which the cutting edge travels from the cutting edge's direction to a side on the open side of the bucket is determined such that the direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle, and the work implement is operated accordingly.

Furthermore, while in the above description a case where a predetermined angle Q for which resistance of soil has a minimal value is used has been described, this is not exclusive, and work implement 2 may be controlled with any predetermined angle set as the excavation angle. The value of the excavation angle is not limited to a fixed value, either. For example, the value of the excavation angle may be changed as time elapses after the excavation mode is started. For example, for a predetermined period of time after the excavation mode is started, i.e., while an excavation process is performed to introduce soil into bucket 8, the excavation angle may be set to a first excavation angle, whereas while the excavation process is performed to scrape soil out of bucket 8, the excavation angle may be set to a second excavation angle.

<Function and Effect>

A function and effect of the present embodiment will be described.

According to the present embodiment, work vehicle CM includes vehicular body 1 and work implement 2, as shown in FIG. 1 Work implement 2 has boom 6 pivotable with respect to vehicular body 1, dipper stick 7 pivotable with respect to boom 6, and bucket 8 pivotable with respect to dipper stick 7. As shown in FIG. 3, work vehicle CM is provided with work implement controller 26. Work implement controller 26 calculates a direction of cutting edge 8a of bucket 8 and determines an excavating direction vector (a direction in which cutting edge 8a travels to a side on the open side of bucket 8) such that the direction of cutting edge 8a of bucket 8 and the direction in which cutting edge 8a travels to the side on the open side of bucket 8 form an excavation angle of a predetermined angle Q, and work implement controller 26 causes an operation of the work implement to be performed in the direction in which the cutting edge travels.

As shown in FIG. 4, causing work implement 2 to perform an excavation process at the excavation angle of the predetermined angle Q for which resistance of soil has a minimal value allows the work implement to operate efficiently in a simple manner.

Work implement controller 26 determines an excavating direction vector such that the calculated direction of cutting edge 8a of bucket 8 and the direction in which cutting edge 8a travels to the side on the open side of bucket 8 form an excavation angle of the predetermined angle Q for a predetermined period of time, and work implement controller 26 causes an operation of the work implement to be performed in the direction in which the cutting edge travels.

As shown in FIG. 4, performing an excavation process at an excavation angle with a small value of resistance of soil for a predetermined period of time allows the work implement to operate efficiently and fuel economy to be improved.

Work vehicle CM is provided with first manipulation lever 25R operated to output a first manipulation command to work implement controller 26 to adjust an amount of pivoting bucket 8 with respect to dipper stick 7 and second manipulation lever 25L operated to output a second manipulation command to work implement controller 26 to adjust an amount of moving bucket 8 for a direction in which cutting edge 8a travels to the side on the open side of bucket 8 from the direction of cutting edge 8a.

As an excavation process is performed in response to manipulation commands via two manipulation levers, the excavation process can be performed more efficiently through a simpler manipulation than a conventional hydraulic excavator's excavating operation in which manipulation levers of three axes for a boom, a dipper stick, and a bucket, respectively, are moved to manipulate the movement of the bucket.

Work implement controller 26 determines whether the current mode is an excavation mode in which work implement 2 performs an operation thereof which is an excavation work. When work implement controller 26 determines that the current mode is the excavation mode in which work implement 2 performs an excavation work, work implement controller 26 accepts first and second manipulation commands via first manipulation lever 25R and second manipulation lever 25L.

When work implement controller 26 determines that the current mode is the excavation mode, work implement controller 26 accepts first and second manipulation commands via two manipulation levers to manipulate bucket 8, and the excavation process can be performed efficiently.

Work implement controller 26 determines, according to an instruction issued as the operator presses excavation mode setting button 25P, whether the current mode is an excavation mode in which work implement 2 performs an operation thereof which is an excavation work.

Whether the current mode is the excavation mode can be determined according to an instruction issued as the operator presses excavation mode setting button 25P, and the work implement can be operated efficiently with the operator's intention reflected.

Work vehicle CM is provided with load sensor 28 to sense a load imposed on bucket 8. Work implement controller 26 determines according to a result of detection by load sensor 28 whether the current mode is a working mode in which work implement 2 performs an operation thereof which is an excavation work.

As whether the current mode is the working mode can be determined according to a result of detection by load sensor 28, the operator's manipulation instruction is unnecessary, and the work implement can be operated efficiently in a simple manner.

According to the present embodiment, work vehicle CM includes vehicular body 1 and work implement 2, as shown in FIG. 1. Work implement 2 has boom 6 pivotable with respect to vehicular body 1, dipper stick 7 pivotable with respect to boom 6, and bucket 8 pivotable with respect to dipper stick 7. A method for controlling work vehicle CM comprises the steps of: calculating a direction of cutting edge 8a of bucket 8; and causing an operation of a work implement to be performed in a direction in which cutting edge 8a travels to a side on the open side of bucket 8 such that the calculated direction of cutting edge 8a of bucket 8 and the direction in which cutting edge 8a travels to the side on the open side of bucket 8 form an excavation angle of a predetermined angle Q.

As shown in FIG. 4, it is possible to cause work implement 2 to perform an excavation process at the excavation angle of the predetermined angle Q for which resistance of soil has a minimal value, and it is possible to operate the work implement efficiently in a simple manner.

While a hydraulic excavator has been described as a work vehicle in the present example, the work vehicle is also applicable to a crawler dozer, a wheel loader and other similar work vehicles.

While the present invention has been described in embodiments, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in any respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims.

REFERENCE SIGNS LIST

1 vehicular body, 2 work implement, 3 revolving unit, 4 operator's cab, 4s operator's seat, 5 traveling unit, 5Cr crawler, 6 boom, 7 dipper stick, 8 bucket, 8a cutting edge, 9 engine room, 10 boom cylinder, 11 dipper stick cylinder, 12 bucket cylinder, 13 boom pin, 14 dipper stick pin, 15 bucket pin, 16 boom cylinder stroke sensor, 17 dipper stick cylinder stroke sensor, 18 bucket cylinder stroke sensor, 19 handrail, 25, 25# manipulation device, 25L second manipulation lever, 25P excavation mode setting button, 25R first manipulation lever, 26, 26# work implement controller, 28 load sensor, 60 hydraulic cylinder, 64 directional control valve, 66 pressure sensor, 200, 200# control system, 300 base station.

Claims

1. A work vehicle comprising:

a vehicular body;

a work implement having a boom pivotable with respect to the vehicular body, a dipper stick pivotable with respect to the boom, and a bucket pivotable with respect to the dipper stick; and

a controller that calculates a direction of a cutting edge of the bucket and determines a direction in which the cutting edge travels to a side on an open side of the bucket such that the calculated direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle, and that causes an operation of the work implement to be performed in the direction in which the cutting edge travels.

2. The work vehicle according to claim 1, wherein the controller determines the direction in which the cutting edge travels to the side on the open side of the bucket such that the calculated direction of the cutting edge of the bucket and the direction in which the cutting edge travels to the side on the open side of the bucket form the excavation angle of the predetermined angle for a predetermined period of time, and the controller causes the operation of the work implement to be performed in the direction in which the cutting edge travels.

3. The work vehicle according to claim 1, further comprising: a first manipulation lever operated to output a first manipulation command to the controller to adjust an amount of pivoting the bucket with respect to the dipper stick; and a second manipulation lever operated to output a second manipulation command to the controller to adjust an amount of moving the bucket for the direction in which the cutting edge travels from the direction of the cutting edge to the side on the open side of the bucket.

4. The work vehicle according to claim 3, wherein

the controller determines whether to cause the operation of the work implement to be performed, and

when the controller determines that the operation of the work implement is caused to be performed, the controller accepts first and second manipulation commands from the first and second manipulation levers.

5. The work vehicle according to claim 4, wherein the controller determines whether to cause the operation of the work implement to be performed in accordance with a manipulation instruction of an operator.

6. The work vehicle according to claim 5, further comprising a load detector that detects a load imposed on the work implement, wherein the controller determines whether to cause the operation of the work implement to be performed according to a result of detection by the load detector.

7. A method for controlling a work vehicle including a work implement having a boom pivotable with respect to a vehicular body, a dipper stick pivotable with respect to the boom, and a bucket pivotable with respect to the dipper stick, comprising:

calculating a direction of a cutting edge of the bucket; and

causing an operation of the work implement to be performed in a direction in which the cutting edge travels to a side on an open side of the bucket such that the direction of the cutting edge of the bucket as calculated and the direction in which the cutting edge travels to the side on the open side of the bucket form an excavation angle of a predetermined angle.