U.S. patent application number 17/271100 was filed with the patent office on 2021-10-21 for blade control device for work machinery.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.). The applicant listed for this patent is KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.), KOBELCO CONSTRUCTION MACHINERY CO., LTD.. Invention is credited to Yusuke KAMIMURA, Satoshi MAEKAWA, Daisuke NODA, Naoki SUGANO, Shohei UEMURA.
Application Number | 20210324605 17/271100 |
Document ID | / |
Family ID | 1000005735334 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210324605 |
Kind Code |
A1 |
SUGANO; Naoki ; et
al. |
October 21, 2021 |
BLADE CONTROL DEVICE FOR WORK MACHINERY
Abstract
A blade operation control part of a blade control device
controls operation of a blade such that when a blade load is equal
to or less than a first load threshold value and a position
deviation is equal to or greater than a position threshold value,
the blade is lowered to make the position deviation approach zero.
The blade operation control part controls operation of the blade
such that the blade is raised regardless of the position deviation
when the blade load is equal to or greater than a second load
threshold value.
Inventors: |
SUGANO; Naoki; (Kobe-shi,
JP) ; MAEKAWA; Satoshi; (Kobe-shi, JP) ;
UEMURA; Shohei; (Kobe-shi, JP) ; NODA; Daisuke;
(Hiroshima, JP) ; KAMIMURA; Yusuke; (Hiroshima,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.)
KOBELCO CONSTRUCTION MACHINERY CO., LTD. |
Kobe-shi
Hiroshima-shi |
|
JP
JP |
|
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO SHO
(Kobe Steel, Ltd.)
Kobe-shi
JP
KOBELCO CONSTRUCTION MACHINERY CO., LTD.
Hiroshima-shi
JP
|
Family ID: |
1000005735334 |
Appl. No.: |
17/271100 |
Filed: |
August 7, 2019 |
PCT Filed: |
August 7, 2019 |
PCT NO: |
PCT/JP2019/031264 |
371 Date: |
February 24, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 3/7609 20130101;
E02F 3/844 20130101; E02F 9/262 20130101; E02F 3/964 20130101 |
International
Class: |
E02F 3/84 20060101
E02F003/84; E02F 9/26 20060101 E02F009/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2018 |
JP |
2018-162282 |
Claims
1. A blade control device which is provided in a work machine
including a machine body and a blade attached to the machine body
so as to be raised and lowered and which controls raising and
lowering operation of the blade, the blade control device
comprising: a target design surface setting part which sets a
target design surface that specifies a target shape of an object to
be dug by the blade; a position information acquiring part which
acquires position information related to the work machine; a blade
position calculating part which calculates a blade position as a
position of the blade on the basis of the position information
acquired by the position information acquiring part; a deviation
calculating part which calculates a position deviation as a
deviation between the blade position and the target design surface;
a blade load acquiring part which acquires a blade load as a load
applied on the blade; a storage part which stores a first load
threshold value as a threshold value of the blade load, a second
load threshold value which is a threshold value of the blade load
and greater than the first load threshold value, and a position
threshold value as a threshold value of the position deviation; and
a blade operation control part which controls operation of the
blade, wherein the blade operation control part controls operation
of the blade such that the blade is lowered to make the position
deviation approach zero when the blade load is equal to or less
than the first load threshold value and the position deviation is
equal to or greater than the position threshold value, and the
blade operation control part controls operation of the blade such
that the blade is raised regardless of the position deviation when
the blade load is equal to or greater than the second load
threshold value.
2. The blade control device according to claim 1, wherein in a case
where the blade load is greater than the first load threshold value
and smaller than the second load threshold value, and the position
deviation is equal to or greater than the position threshold value,
a relative position of the blade with respect to the machine body
is maintained.
3. The blade control device according to claim 1, wherein in a case
where the blade load is greater than the first load threshold value
and smaller than the second load threshold value, and the position
deviation is smaller than the position threshold value, the blade
operation control part controls operation of the blade such that
the position deviation approaches zero.
4. The blade control device according to claim claims 1, wherein
the position threshold value is a first position threshold value,
the storage part further stores a second position threshold value
which is a threshold value of the position deviation and is smaller
than the first position threshold value, and the blade operation
control part controls operation of the blade such that the blade is
raised to make the position deviation approach zero in a case where
the blade load is equal to or less than the first load threshold
value and the position deviation is equal to or less than the
second position threshold value.
Description
TECHNICAL FIELD
[0001] The present invention relates to a blade control device
provided in a work machine including a blade.
BACKGROUND ART
[0002] Conventionally, a work machine including a blade for use in
digging of the ground, grading, transport of sediments, and the
like has been used widely. In such a work machine, while conducting
travelling manipulation, an operator conducts manipulation of
raising and lowering a blade to adjust a blade position (a height
of a blade edge) and to conduct digging of the ground, grading, or
the like.
[0003] Patent Literature 1 discloses a blade control system which
automatically controls the blade position. The blade control system
recited in Patent Literature 1 executes digging control in a case
where a distance determination part determines that a distance
between a design surface and a blade edge exceeds a first distance,
executes grading control in a case where the distance determination
part determines that the distance between the design surface and
the blade edge goes below a second distance, and executes digging
control or grading control in a case where the distance
determination part determines that the distance between the design
surface and the blade edge is equal to or less than the first
distance and equal to or greater than the second distance. In
Patent Literature 1, the digging control is control for maintaining
a blade load at a target load in order to conduct efficient digging
work. The grading control is control for maintaining the distance
between the blade edge and the design surface at a target distance
in order to level the ground into a target shape.
[0004] The blade control system of Patent Literature 1, however,
has a problem that control selected from the digging control and
the grading control cannot be control appropriate for an actual
digging condition. In a case, for example, where the distance
between the design surface and the blade edge goes below the second
distance, even if a blade load is large, the grading control, i.e.,
the control for maintaining the distance between the blade edge and
the design surface at a target distance, is conducted without fail,
so that the blade load might be excessively large depending on a
state (e.g. hardness of sediments, a kind of sediments, etc.) of
the ground to be dug. This might cause a work machine to be stuck.
By contrast, in a case where the distance between the blade edge
and the design surface exceeds the first distance, because the
digging control is conducted without grading control even when a
blade load is so small that control (grading control) to match the
blade edge with the design surface can be conducted, high work
execution efficiency cannot be obtained.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: JP 5247939 B
SUMMARY OF INVENTION
[0006] An object of the present invention is to provide a blade
control device which is provided in a work machine including a
blade and is capable of selecting control appropriate for an actual
digging condition.
[0007] The blade control device of the present invention is a
device which is provided in a work machine including a machine body
and a blade attached to the machine body so as to be raised and
lowered and which controls raising and lowering operation of the
blade. The blade control device includes a target design surface
setting part which sets a target design surface that specifies a
target shape of an object to be dug by the blade; a position
information acquiring part which acquires position information
related to the work machine; a blade position calculating part
which calculates a blade position as a position of the blade on the
basis of the position information acquired by the position
information acquiring part; a deviation calculating part which
calculates a position deviation as a deviation between the blade
position and the target design surface; a blade load acquiring part
which acquires a blade load as a load applied on the blade; a
storage part which stores a first load threshold value as a
threshold value of the blade load, a second load threshold value
which is a threshold value of the blade load and greater than the
first load threshold value, and a position threshold value as a
threshold value of the position deviation; and a blade operation
control part which controls operation of the blade, in which the
blade operation control part controls operation of the blade such
that the blade is lowered to make the position deviation approach
zero when the blade load is equal to or less than the first load
threshold value and the position deviation is equal to or greater
than the position threshold value. The blade operation control part
controls operation of the blade such that the blade is raised
regardless of the position deviation when the blade load is equal
to or greater than the second load threshold value.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a side view showing a hydraulic excavator as an
example of a work machine in which a blade control device according
to an embodiment of the present invention is provided.
[0009] FIG. 2 is a block diagram showing a main function of the
blade control device according to the embodiment.
[0010] FIG. 3 is a schematic view for explaining a relationship
among a target design surface, a present surface, and a position
deviation.
[0011] FIG. 4 is a flowchart showing one example of control
operation executed by a controller included in the blade control
device according to the embodiment.
[0012] FIG. 5 is a graph showing one example of control for
operation of a blade on the basis of a position deviation as a
deviation between the blade position and the target design surface
in the blade control device according to the embodiment.
[0013] FIG. 6 is a graph showing another example of control for
operation of the blade on the basis of a position deviation as a
deviation between the blade position and the target design surface
in the blade control device according to the embodiment.
[0014] FIG. 7 is a graph showing a further example of control for
operation of the blade on the basis of a position deviation as a
deviation between the blade position and the target design surface
in the blade control device according to the embodiment.
[0015] FIG. 8 is a graph showing one example of control for
operation of the blade on the basis of a blade load in the blade
control device according to the embodiment.
DESCRIPTION OF EMBODIMENTS
[0016] A preferred embodiment of the present invention will be
described with reference to the drawings.
Overall Structure of Work Machine
[0017] FIG. 1 is a side view showing a hydraulic excavator 1 as an
example of a work machine in which a blade control device according
to an embodiment of the present invention is provided. The
hydraulic excavator 1 includes a travelling device 2 (lower
travelling body) capable of travelling on the ground G, a vehicle
body 3 (upper slewing body) mounted on the travelling device 2, a
work device mounted on the vehicle body 3, and a blade 4 (dozer)
mounted on the travelling device 2 or the vehicle body 3. The
travelling device 2 and the vehicle body 3 constitute a machine
body of the work machine. The vehicle body 3 has a slewing frame,
an engine, a driver's room, and the like.
[0018] The work device mounted on the vehicle body 3 includes a
boom 5, an arm 6, and a bucket 7. The boom 5 has a base end portion
supported at a front end of the slewing frame so as to go up and
down, i.e., to be turnable around a horizontal axis, and a distal
end portion on the opposite side. The arm 6 has a base end portion
attached to the distal end portion of the boom 5 so as to be
turnable around the horizontal axis, and a distal end portion on
the opposite side. The bucket 7 is turnably attached to the distal
end portion of the arm 6.
[0019] The hydraulic excavator 1 has a boom cylinder, an arm
cylinder, and a bucket cylinder provided for the boom 5, the arm 6,
and the bucket 7, respectively. The boom cylinder is interposed
between the vehicle body 3 and the boom 5 and extends and contracts
so as to cause the boom 5 to conduct up-down operation. The arm
cylinder is interposed between the boom 5 and the arm 6 and extends
and contracts so as to cause the arm 6 to conduct turning
operation. The bucket cylinder is interposed between the arm 6 and
the bucket 7 and extends and contracts so as to cause the bucket 7
to conduct turning operation.
[0020] The blade 4 mounted on the travelling device 2 or the
vehicle body 3 is provided for conducting digging of the ground,
grading, transport of sediments, and the like. Specifically, the
blade 4 is supported by a lift frame 4a, and the lift frame 4a is
supported to be turnable around a horizontal axis 4b with respect
to the travelling device 2. Accordingly, the blade 4 can be
displaced in an up-down direction with respect to the travelling
device 2.
[0021] The hydraulic excavator 1 has a lift cylinder 8 provided for
the blade 4. The lift cylinder 8 has a head chamber 8h and a rod
chamber 8r (see FIG. 1), and extends to thereby cause the blade 4
to move in a down direction when a hydraulic oil is supplied to the
head chamber 8h, as well as discharging the hydraulic oil in the
rod chamber 8r, and also contracts to thereby cause the blade 4 to
move in an up direction when the hydraulic oil is supplied to the
rod chamber 8r, as well as discharging the hydraulic oil in the
head chamber 8h.
[0022] The hydraulic excavator 1 has a hydraulic circuit not shown.
The hydraulic circuit includes the boom cylinder, the arm cylinder,
the bucket cylinder, and the lift cylinder 8. The hydraulic circuit
further includes a hydraulic pump 9 (see FIG. 1), a lift cylinder
control proportional valve 41 (see FIG. 2), and a lift cylinder
flow rate control valve not shown.
Blade Control Device
[0023] FIG. 2 is a block diagram showing a main function of a blade
control device 100. The blade control device 100 is provided for
controlling raising and lowering operation of the blade 4. The
blade control device 100 includes a controller 10 (mechatronic
controller), a position information acquiring part, a blade load
acquiring part 34, an automatic control switch 35, and a travelling
lever 36 for manipulating the travelling device 2. The controller
10, which is configured with, for example, a microcomputer,
controls operation of each element included in the hydraulic
circuit.
[0024] The position information acquiring part is configured to
acquire position information about the hydraulic excavator 1.
Specifically, in the present embodiment, the position information
acquiring part includes a vehicle body position acquiring part 31,
a vehicle body angle acquiring part 32, and a blade angle acquiring
part 33. The vehicle body position acquiring part 31 is configured
to acquire a vehicle body position as a position of the machine
body. The vehicle body position acquiring part 31 is configured
with, for example, a receiver, such as a GNSS receiver (GNSS
sensor), capable of receiving satellite data (positioning signal)
from a satellite measurement system, such as GNSS (Global
Navigation Satellite System), and receives GNSS data indicative of
a vehicle body position as a position of the vehicle body 3 in a
global coordinate system. The global coordinate system is a
three-dimensional coordinate system using an origin point defined
on the earth as a reference, which is a coordinate system
indicating an absolute position defined by the satellite
measurement system.
[0025] The vehicle body angle acquiring part 32 is configured to
acquire a vehicle body angle as an angle of the vehicle body 3. The
vehicle body angle acquiring part 32 is configured with, for
example, a vehicle body angle sensor which detects an angle of the
vehicle body 3 in a global coordinate system. Specifically, the
vehicle body angle sensor may be configured with, for example, one
or a plurality of receivers provided in the machine body and
capable of receiving satellite data (positioning signal) from a
satellite measurement system.
[0026] The blade angle acquiring part 33 is configured to acquire
an angle of the blade 4. The blade angle acquiring part 33 is
configured with, for example, a blade angle sensor which detects
the angle of the blade 4 in a global coordinate system.
Specifically, the blade angle sensor may be configured with, for
example, one or a plurality of receivers provided in the machine
body and capable of receiving satellite data (positioning signal)
from a satellite measurement system.
[0027] A local coordinate system may be used in place of the global
coordinate system. Both the global coordinate system and the local
coordinate system may be used together. Examples of the local
coordinate system include a three-dimensional coordinate system
using the vehicle body position as a reference and a
three-dimensional coordinate system using a specific position at a
work site as a reference. In the above case, the vehicle body angle
sensor may be configured with, for example, an inertia measurement
device, or may be configured with, for example, the inertia
measurement device and the receiver capable of receiving the
satellite data. The inertia measurement device may be configured to
be capable of, for example, measuring an acceleration and an
angular velocity of the vehicle body 3, and detecting an
inclination (e.g., a pitch indicative of rotation with respect to
an X-axis, a yaw indicative of rotation with respect to a Y-axis,
and a roll indicative of rotation with respect to a Z-axis) of the
vehicle body 3 on the basis of a measurement result. The blade
angle sensor may be configured with, for example, a stroke sensor
which detects a cylinder stroke of the blade cylinder 8, or may be
configured with the stroke sensor and the receiver capable of
receiving the satellite data.
[0028] Although, in the present embodiment, the vehicle body
position acquiring part 31 and the vehicle body angle acquiring
part 32 are attached to an upper portion of the vehicle body 3 and
the blade angle acquiring part 33 is attached to an upper portion
of the blade 4 as shown in FIG. 1, the attachment positions are not
limited to the specific example shown in FIG. 1. Detection signals
as electrical signals generated by these acquiring parts 31, 32,
and 33 are input to the controller 10.
[0029] In the present embodiment, the blade load acquiring part 34
is configured to acquire a blade load as a load applied on the
blade 4 during digging work. The blade load corresponds to, for
example, a pump pressure of the hydraulic pump 9 which drives the
blade 4. Accordingly, the blade load acquiring part 34 is capable
of detecting the blade load by detecting the pump pressure. In the
present embodiment, the blade load acquiring part 34 includes a
head pressure sensor 34H which detects a head pressure P1 as a
pressure of a hydraulic oil in the head chamber 8h of the lift
cylinder 8, and a rod pressure sensor 34R which detects a rod
pressure P2 as a pressure of a hydraulic oil in the rod chamber 8r
of the lift cylinder 8. The sensors 34H and 34R respectively
convert their detected physical quantities into detection signals
as electrical signals corresponding to the physical quantities and
input the detection signals to the controller 10.
[0030] The automatic control switch 35 is arranged in the driver's
room and is electrically connected to the controller 10. Upon
receiving manipulation for switching a control mode of the
controller 10 from a manual manipulation mode to an automatic
control mode, the automatic control switch 35 inputs a mode command
signal related to the manipulation to the controller 10. The
controller 10 switches setting of the control mode from the manual
manipulation mode to the automatic control mode by the mode command
signal input from the automatic control switch 35.
[0031] In the automatic control mode, the controller 10 is
configured to automatically control operation of the lift cylinder
8 such that an execution surface to be executed by the blade 4
approaches a target design surface set in advance. When a command
value (command current) to the lift cylinder control proportional
valve 41 for controlling operation of the lift cylinder 8 is output
from the controller 10, a secondary pressure of the proportional
valve 41 changes according to the command value and opening of the
lift cylinder flow rate control valve changes according to the
secondary pressure. As a result, a supply flow and a supply
direction of a hydraulic oil to be supplied from the hydraulic pump
9 to the lift cylinder 8 via the lift cylinder flow rate control
valve change to control an operation speed and a driving direction
of the lift cylinder 8. On the other hand, in the manual
manipulation mode, when a worker manipulates the travelling lever
36, a manipulation signal of the manipulation is input to the
controller 10, and the command value to the lift cylinder control
proportional valve 41 or a command value to the lift cylinder flow
rate control valve is output from the controller 10 according to an
amount of manipulation of a manipulation lever not shown for
manipulating raising and lowering of the blade 4.
[0032] The controller 10 has a target design surface setting part
11, a blade position calculating part 12, a storage part 13, a
deviation calculating part 14, a blade operation control part 15, a
threshold value setting part 16 as a function for executing the
automatic control.
[0033] The target design surface setting part 11 sets a target
design surface which specifies a target shape of an object to be
dug by the blade 4. The target design surface setting part 11 may
store data of a design surface input by a target design surface
input part provided in the driver's room and set the design surface
as a target design surface. The target design surface setting part
11 may also store data of a design surface acquired via various
kinds of storage media, a communication network, or the like and
set the design surface as a target design surface. The target
design surface is a surface which specifies a three-dimensional
design topography as a target shape of the ground which is an
object to be dug. The target design surface may be specified by
external data such as BIM or CIM (Building/Construction Information
Modeling, Management). The target design surface may be set using a
position of the work machine as a reference.
[0034] The blade position calculating part 12 calculates a blade
position as a position of the blade 4 in the global coordinate
system on the basis of the position information acquired by the
position information acquiring part. In the present embodiment, the
blade position calculating part 12 calculates the blade position on
the basis of the vehicle body position acquired by the vehicle body
position acquiring part 31, the vehicle body angle acquired by the
vehicle body angle acquiring part 32, and the angle of the blade 4
acquired by the blade angle acquiring part 33. In other words, the
blade position is calculated from a sum of a vector from a
reference point to the vehicle body position and a vector from the
vehicle body position to the blade position. Although in the
present embodiment, a blade position is thus calculated from a
relative angle between the vehicle body angle and the angle of the
blade 4 in the global coordinate system, a blade position
calculation method is not limited thereto. The blade position may
be calculated on the basis of, for example, a length of the lift
cylinder 8, or may be calculated on the basis of GNSS data received
by a GNSS receiver (GNSS sensor) attached to the blade 4.
[0035] The deviation calculating part 14 calculates a position
deviation .DELTA.Z as a deviation between the blade position and
the target design surface SD.
[0036] FIG. 3 is a schematic view for explaining a relationship
among a target design surface SD, a present surface SP, and a
position deviation .DELTA.Z. In FIG. 3, the hydraulic excavator 1
(work machine) is illustrated in a simplified manner. Although in
the present embodiment, the blade position is set at a blade edge
position (a position of a lower edge of a distal end of the blade
4) as the distal end of the blade 4 as shown in FIG. 3, the blade
position may be set at other part of the blade 4. The position
deviation .DELTA.Z is a deviation between the blade position and
the target design surface SD. In other words, the position
deviation .DELTA.Z can be obtained by subtracting a height of the
target design surface SD from the blade position (a blade edge
height of the blade 4). The present surface SP shown in FIG. 3 is
the ground which is an object to be dug.
[0037] The threshold value setting part 16 sets a first load
threshold value f1, a second load threshold value f2, a first
position threshold value Z1, and a second position threshold value
Z2 for use in calculation of the blade operation control part 15.
These threshold values may be manually input to the controller 10
by a worker before the digging work or appropriately calculated by
the controller 10 during the digging work.
[0038] The storage part 13 stores the first load threshold value
f1, the second load threshold value f2, the first position
threshold value Z1, and the second position threshold value Z2 set
by the threshold value setting part 16.
[0039] The first load threshold value f1 is set to be a value
corresponding to a proper blade load f with which the hydraulic
excavator 1 can stably travel. The second load threshold value f2
is a value set to realize stably efficient digging operation. The
second load threshold value f2 is a value set to prevent occurrence
of such a situation that the blade load f becomes excessively large
to cause a stuck condition (a state where the blade load f becomes
excessively so large that the work machine has difficult in
advancing). Accordingly, the second load threshold value f2 is set
to be a value greater than the first load threshold value f1. The
second load threshold value f2 is preferably set to be a value
smaller than the blade load f with which such a situation as
described above occurs. In other words, the second load threshold
value f2 is preferably set to be a value with which the work
machine can travel even when the blade load f reaches the second
load threshold value C.
[0040] The first position threshold value Z1 is a value as a
reference for determining whether or not to control blade operation
so as to lower the blade 4 such that a position deviation
approaches zero in a case where the blade load f is equal to or
less than the first load threshold value f1. The first position
threshold value Z1 is also a value as a reference for determining
whether or not to maintain a relative position of the blade 4 with
respect to the machine body in a case where the blade load f is
within an intermediate load region, i.e., where the blade load f is
greater than the first load threshold value f1 and smaller than the
second load threshold value f2. The first position threshold value
Z1 is set to be, for example, zero or a positive value. The second
position threshold value Z2 is a value as a reference for
determining whether or not to control the blade operation so as to
raise the blade 4 such that the position deviation approaches zero
in a case where the blade load f is within the intermediate load
region. Accordingly, the second position threshold value Z2 is set
to be a value smaller than the first position threshold value
Z1.
[0041] The blade operation control part 15 calculates and outputs a
command value to the lift cylinder control proportional valve 41
for controlling operation of the lift cylinder 8. There are input
to the blade operation control part 15, an automatic control switch
manipulation signal of the automatic control switch 35, a
travelling lever manipulation signal of the travelling lever 36,
the blade load f acquired by the blade load acquiring part 34, each
threshold value set by the threshold value setting part 16 and
stored in the storage part 13, and the position deviation .DELTA.Z
calculated by the deviation calculating part 14, on the basis of
which, a command current to be output to the lift cylinder control
proportional valve 41 is calculated.
[0042] Next, description will be made of control operation
conducted by the controller 10 for the driving of the blade 4 in
the automatic control mode with reference to the flowchart of FIG.
4.
[0043] When the automatic control switch 35 (see FIG. 2) is turned
on, the controller 10 conducts initial operation for the automatic
control (Step S0). In the initial operation, the controller 10
takes in a signal to be input to the controller 10, specifically, a
detection signal of each sensor and designation signals. The
designation signals include a signal for a target design surface
designated by manipulation of the target design surface input part
by an operator, a signal for a blade load f acquired by the blade
load acquiring part 34, a signal for the vehicle body position
acquired by the vehicle body position acquiring part 31, a signal
for a vehicle body angle acquired by the vehicle body angle
acquiring part 32, a signal for an angle of the blade 4 acquired by
the blade angle acquiring part 33, a signal for a travelling speed
corresponding to manipulation received by the travelling lever 36,
and the like. The controller 10 acquires an initial state of the
hydraulic excavator 1 on the basis of these designation signals.
The target design surface setting part 11 of the controller 10 sets
a target design surface on the basis of the signal for the target
design surface. Then, the blade operation control part 15 of the
controller 10 controls operation of the blade 4 in the following
manner.
[0044] The blade operation control part 15 determines whether the
blade load f acquired by the blade load acquiring part 34 is equal
to or greater than the second load threshold value f2 or not (Step
S1). In a case where the blade load f is equal to or greater than
the second load threshold value f2 (YES in Step S1), the blade
operation control part 15 controls operation of the blade 4 such
that the blade 4 is raised (Step S2), and the controller 10 again
conducts the processing of Step S1.
[0045] In a case where the blade load f is smaller than the second
load threshold value f2 (NO in Step S1), the blade operation
control part 15 determines whether the blade load f is equal to or
less than the first load threshold value f1 or not (Step S3).
[0046] In a case where the blade load f is equal to or less than
the first load threshold value f1 (YES in Step S3), the blade
operation control part 15 determines whether the position deviation
.DELTA.Z is equal to or greater than the first position threshold
value Z1 or not (Step S4).
[0047] In a case where the position deviation .DELTA.Z is equal to
or greater than the first position threshold value Z1 (YES in Step
S4), the blade operation control part 15 conducts grading control
(Step S5). Specifically, the blade operation control part 15
controls the operation of the blade 4 such that the blade 4 is
lowered to make the position deviation .DELTA.Z approach zero (Step
S5), and the controller 10 again conducts the processing of Step
S1.
[0048] On the other hand, in a case where the position deviation
.DELTA.Z is smaller than the first position threshold value Z1 (NO
in Step S4), the blade operation control part 15 determines whether
the position deviation .DELTA.Z is equal to or less than the second
position threshold value Z2 or not (Step S6).
[0049] In a case where the position deviation .DELTA.Z is equal to
or less than the second position threshold value Z2 (YES in Step
S6), the blade operation control part 15 conducts the grading
control. Specifically, the blade operation control part 15 controls
the operation of the blade 4 such that the blade 4 is raised to
make the position deviation .DELTA.Z approach zero (Step S7), and
the controller 10 again conducts the processing of Step S1.
[0050] In a case where the position deviation .DELTA.Z is smaller
than the first position threshold value Z1 (NO in Step S4) and the
position deviation .DELTA.Z is greater than the second position
threshold value Z2 (NO in Step S6), the blade operation control
part 15 refrains from conducting such control (control for the
raising operation or the lowering operation of the blade 4) to
change the relative position of the blade 4 with respect to the
machine body, so that the relative position is maintained and the
controller 10 again conducts the processing of Step S1.
[0051] In a case where the blade load f is smaller than the second
load threshold value f2 (NO in Step S1) and the blade load f is
greater than the first load threshold value f1 (NO in Step S3),
i.e., the blade load f is within the intermediate load region, the
blade operation control part 15 determines whether the position
deviation .DELTA.Z is equal to or greater than the first position
threshold value Z1 or not (Step S8).
[0052] In a case where the position deviation .DELTA.Z is equal to
or greater than the first position threshold value Z1 (YES in Step
S8), the blade operation control part 15 refrains from conducting
such control (control for the raising operation or the lowering
operation of the blade 4) to change the relative position of the
blade 4 with respect to the machine body, so that the relative
position is maintained (Step S9). In other words, the blade
operation control part 15 does not output a command to the lift
cylinder control proportional valve 41. That is, as an amount of
lift of the blade 4 with respect to the machine body, a previous
value is maintained. Thereafter, the controller 10 again conducts
the processing of Step S1.
[0053] On the other hand, in a case where the position deviation
.DELTA.Z is smaller than the first position threshold value Z1 (NO
in Step S8), the blade operation control part 15 conducts the
grading control (Step S10). Specifically, the blade operation
control part 15 controls the operation of the blade 4 such that the
blade 4 is lowered or raised to make the position deviation
.DELTA.Z approach zero (Step S10), and the controller 10 again
conducts the processing of Step S1.
[0054] The above-described control by the blade control device 100
shown in the flowchart of FIG. 4 will be summarized as follows. The
controller 10 of the blade control device 100 executes a first
control mode, a second control mode, and a third control mode. The
first control mode is a mode for conducting the grading control,
the second control mode is a mode for conducting blade raising
control (lift-up control), and the third control mode is a mode for
conducting blade maintaining control (lift maintaining
control).
[0055] The grading control for the first control mode is to control
the operation of the blade 4 such that the position deviation
.DELTA.Z approaches zero. In other words, in the grading control,
the operation of the blade 4 is controlled such that the blade edge
(the blade position) of the blade 4 is substantially matched with a
target design surface. The first control mode is conducted in a
case where the blade load f is equal to or less than the first load
threshold value f1. Specifically, in the present embodiment, the
first control mode is conducted in a case where the blade load f is
equal to or less than the first load threshold value n and the
position deviation .DELTA.Z is equal to or greater than the first
position threshold value Z1 (Step S5). Additionally, the first
control mode is conducted also in a case where the blade load f is
equal to or less than the first load threshold value f1 and the
position deviation .DELTA.Z is equal to or less than the second
position threshold value Z2 (Step S7). Further, the first control
mode is conducted also in a case where within the intermediate load
region, the position deviation .DELTA.Z is smaller than the first
position threshold value Z1 (Step S10).
[0056] In the second control mode, the operation of the blade 4 is
controlled such that the blade 4 is raised. The second control mode
is conducted in a case where the blade load f is equal to or
greater than the second load threshold value f2 (Step S2).
[0057] In the third control mode, the relative position of the
blade 4 with respect to the machine body is maintained. The third
control mode is conducted in a case where within the intermediate
load region, the position deviation .DELTA.Z is equal to or greater
than the first position threshold value Z1 (Step S9). Additionally,
in the present embodiment, the third control mode is conducted also
in a case where the blade load f is equal to or less than the first
load threshold value f1 and the position deviation .DELTA.Z is
smaller than the first position threshold value Z1 and greater than
the second position threshold value Z2 (NO in Step S6).
[0058] FIG. 5, FIG. 6, and FIG. 7 are graphs respectively showing
examples of control for the operation of the blade 4 on the basis
of the position deviation .DELTA.Z between the blade position and
the target design surface SD. The control for the operation of the
blade 4 shown in FIG. 5, FIG. 6, and FIG. 7 is used for the grading
control in the first control mode.
[0059] In the specific example shown in FIG. 5, the first position
threshold value Z1 is set to be a positive value and the second
position threshold value Z2 is set to be zero. In the specific
example shown in FIG. 6, the first position threshold value Z1 is
set to be a positive value and the second position threshold value
Z2 is set to be a negative value. In the specific example shown in
FIG. 7, only the first position threshold value Z1 is set and the
second position threshold value Z2 is not set. As described above,
the position deviation .DELTA.Z is a value obtained by subtracting
the height of the target design surface SD from the blade position
(the blade edge height of the blade 4). Accordingly, in a case
where the blade position is higher than the height of the target
design surface SD, the position deviation .DELTA.Z has a positive
value and in a case where the blade position is lower than the
height of the target design surface SD, the position deviation
.DELTA.Z has a negative value.
[0060] In the control examples shown in FIG. 5, FIG. 6, and FIG. 7,
in a case where the position deviation .DELTA.Z is equal to or
greater than the first position threshold value Z1 (YES in Step
S4), as the position deviation .DELTA.Z is increased, a command
value of a blade lowering command (lift-down command) is increased.
Additionally, in these control examples, in a case where the
position deviation .DELTA.Z is equal to or greater than a
predetermined value, the command value is set to be a fixed value
(maximum value). It may be configured that when the position
deviation .DELTA.Z becomes equal to or greater than the first
position threshold value Z1, the command value is immediately set
to be a fixed value (maximum value).
[0061] As the command value is increased, the operation speed of
the lift cylinder 8 is increased and an operation speed of the
blade 4 is increased.
[0062] In the control examples shown in FIG. 5 and FIG. 6, the
first position threshold value Z1 is set to be a positive value
slightly greater than zero, and in the control example shown in
FIG. 7, the first position threshold value Z1 is set to be
zero.
[0063] In the control examples shown in FIG. 5 and FIG. 6, in a
case where the position deviation .DELTA.Z is equal to or less than
the second position threshold value Z2 (YES in Step S6), as the
position deviation .DELTA.Z is decreased, a command value of a
blade raising command (lift-up command) is increased. In the
control example shown in FIG. 7, in a case where the position
deviation .DELTA.Z is equal to or less than the first position
threshold value Z1, as the position deviation .DELTA.Z is
decreased, the command value of the blade raising command (lift-up
command) is increased. In these control examples, in a case where
the position deviation .DELTA.Z is equal to or less than the
predetermined value, the command value is set to be a fixed value
(maximum value). It may be configured that when the position
deviation .DELTA.Z becomes equal to or less than the second
position threshold value Z2, the command value is immediately set
to be a fixed value (maximum value).
[0064] In the control example shown in FIG. 5, the second position
threshold value Z2 is set to be zero, and in the control example
shown in FIG. 6, the second position threshold value Z2 is set to
be a negative value slightly smaller than zero. In the control
example shown in FIG. 7, the first position threshold value Z1 is
set to be zero.
[0065] In the control examples shown in FIG. 5 and FIG. 6, in a
case where the position deviation .DELTA.Z is smaller than the
first position threshold value Z1 and greater than the second
position threshold value Z2 (NO in Step S6), neither blade lowering
operation (lift-down) nor blade raising operation (lift-up) is
conducted, so that the relative position of the blade 4 with
respect to the machine body is maintained (the above-described
third control mode). By thus providing, in a region in which the
position deviation .DELTA.Z is near zero, a region (dead zone) in
which the relative position is maintained, excessive occurrence of
up-down movement of the blade 4 can be suppressed in the region in
which the position deviation .DELTA.Z is near zero.
[0066] When a condition for the execution of the first control mode
is satisfied in a region where the blade load f is smaller than the
second load threshold value f2, in a case where the blade edge
height of the blade 4 is greater than the target design surface SD,
the blade lowering operation (lift-down) is executed such that as
the position deviation .DELTA.Z is increased, the command value of
the blade lowering command (lift-down command) is increased as in
the control examples shown in FIG. 5, FIG. 6, and FIG. 7. On the
other hand, in a case where the blade edge height of the blade 4 is
smaller than the target design surface SD, the blade raising
operation (lift-up) is executed such that as the position deviation
.DELTA.Z is decreased (according to an increase in an absolute
value of the position deviation .DELTA.Z), the command value of the
blade raising command (lift-up command) is increased. As a result
of execution of such first control mode, an amount of lift (the
relative position of the blade 4 with respect to the machine body)
is controlled such that the blade edge height of the blade 4 is
matched with the height of the target design surface SD to thereby
conduct grading by the blade 4.
[0067] FIG. 8 is a graph showing one example of control for
operation of the blade 4 on the basis of the blade load f. The
control of the operation of the blade 4 shown in FIG. 8 is used for
the blade raising control (lift-up control) in the second control
mode.
[0068] In the control example in FIG. 8, in a case where the blade
load f is equal to or greater than the second load threshold value
f2 (YES in Step S1), as the blade load f is increased, the command
value of the blade raising command (lift-up command) is increased.
Also in this control example, in a case where the blade load f is
equal to or greater than a predetermined value, the command value
is set to a fixed value (maximum value). It may be configured that
when the blade load f becomes equal to or greater than the second
load threshold value f2, the command value is immediately set to
the fixed value (maximum value).
[0069] In a case where the blade load f is equal to or greater than
the second load threshold value f2 as in the control example shown
in FIG. 8, when the second control mode is executed, the lift-up
control is conducted according to an increase in the blade load f,
so that the blade edge of the blade 4 is raised to reduce the blade
load f. This prevents travelling of the work machine from being
stuck due to an increase in the blade load f.
[0070] In a case where in the intermediate load region, the
position deviation .DELTA.Z is equal to or greater than the first
position threshold value Z1 (YES in Step S8), the third control
mode is executed to thereby maintain the relative position of the
blade 4 with respect to the machine body. As a result, since
digging is conducted while the blade edge height of the blade 4 is
fixed within a range in which the travelling of the work machine is
not stuck, unnecessary up-down movement of the blade 4 is
suppressed to obtain an effect of smoothing the execution surface
(digging surface).
[0071] Further, in a case where the position deviation .DELTA.Z is
smaller than the first position threshold value Z1 in the
intermediate load region (NO in Step S8), the first control mode is
executed. Here, when the second position threshold value Z2 (the
first position threshold value Z1 in the control example in FIG. 7)
is set to be, for example, zero as in the control example in FIG.
5, in a case where the blade edge height of the blade 4 is smaller
than the target design surface SD, the blade raising operation
(lift-up) is executed in the first control mode, resulting in
obtaining an effect of suppressing occurrence of a problem of
excessive digging caused by a reduction of the blade edge height of
the blade 4 to be smaller than the target design surface SD.
[0072] The first position threshold value Z1 may be set to an
appropriate positive value as shown in the control examples in FIG.
5 and FIG. 6. In these cases, in a case where the blade load f is
between the first position threshold value Z1 and the second
position threshold value Z2, and the blade edge height of the blade
4 is greater than the target design surface SD, when the position
deviation .DELTA.Z is smaller than the first position threshold
value Z1, the blade lowering operation (lift-down) is executed.
This enables grading to be conducted in which the blade edge height
of the blade 4 is matched with the height of the target design
surface SD. When the first position threshold value Z1 is set to be
too large a value, however, the blade lowering operation
(lift-down) is executed even when the blade load f is between the
first load threshold value f1 and the second load threshold value
f2, and the blade edge height of the blade 4 is in a state of being
relatively greatly away from the height of the target design
surface SD. In such a case, the blade load f is increased to
immediately become equal to or greater than the second load
threshold value f2, resulting in increasing a possibility of
execution of the blade raising operation (lift-up). In such a case,
the blade lowering operation (lift-down) and the blade raising
operation (lift-up) are frequently conducted, so that the execution
surface (digging surface) is likely to have waviness (heave). It is
accordingly preferable to set the first position threshold value Z1
to a value to such an extent that prevents the blade load f from
becoming equal to or greater than the second load threshold value
f2 even when the position deviation .DELTA.Z becomes smaller than
the first position threshold value Z1 and greater than zero, so
that the blade lowering operation (lift-down) is conducted. With
the first position threshold value Z1 set to such a value, even
when the position deviation .DELTA.Z becomes smaller than the first
position threshold value Z1 to cause execution of the blade
lowering operation (lift-down) and the blade load f is gradually
increased, the blade load f is unlikely to become equal to or
greater than the second load threshold value f2. Therefore, an
effect is obtained of suppressing generation of waviness on the
execution surface caused by frequent up-down movement of the blade
4 and enabling stable grading control to be executed within the
intermediate load region, thereby increasing work execution
efficiency.
[0073] The present invention is not limited to the above-described
embodiment. The present invention may include the following modes,
for example.
[0074] A work machine to which the blade control device according
to the present invention is applied is not limited to a hydraulic
excavator. The present invention is widely applicable to another
work machine provided with a blade, such as a wheel loader, a
bulldozer, and a grader.
[0075] As described in the foregoing, a blade control device is
provided which is capable of selecting control appropriate for an
actual digging condition.
[0076] The blade control device is a device which is provided in a
work machine including a machine body and a blade attached to the
machine body so as to be raised and lowered and which controls
raising and lowering operation of the blade. The blade control
device includes a target design surface setting part which sets a
target design surface that specifies a target shape of an object to
be dug by the blade; a position information acquiring part which
acquires position information related to the work machine; a blade
position calculating part which calculates a blade position as a
position of the blade on the basis of the position information
acquired by the position information acquiring part; a deviation
calculating part which calculates a position deviation as a
deviation between the blade position and the target design surface;
a blade load acquiring part which acquires a blade load as a load
applied on the blade; a storage part which stores a first load
threshold value as a threshold value of the blade load, a second
load threshold value which is a threshold value of the blade load
and greater than the first load threshold value, and a position
threshold value as a threshold value of the position deviation; and
a blade operation control part which controls operation of the
blade, in which the blade operation control part controls operation
of the blade such that the blade is lowered to make the position
deviation approach zero when the blade load is equal to or less
than the first load threshold value and the position deviation is
equal to or greater than the position threshold value. The blade
operation control part controls operation of the blade such that
the blade is raised regardless of the position deviation when the
blade load is equal to or greater than the second load threshold
value.
[0077] Since the above-described control is conducted in the blade
control device, control appropriate for actual digging can be
selected. Specifically, the control is conducted in the following
manner. In the blade control device, even in a case where the
position deviation has a value equal to or greater than the
position threshold value, when the blade load has a value equal to
or less than the first load threshold value, control to make a
blade position approach a target design surface is conducted. Since
the control enables an execution surface for a blade to quickly
approach the target design surface, work execution efficiency is
improved. Additionally, in the blade control device, when a blade
load has a value equal to or greater than the second load threshold
value, even if the position deviation is small, control for raising
the blade is conducted irrespective of the position deviation. This
control restrains a blade load from becoming excessively large
irrespective of a state of the ground to be dug and accordingly
suppresses the work machine from being stuck.
[0078] In the blade control device, in a case where the blade load
is greater than the first load threshold value and smaller than the
second load threshold value, and the position deviation is equal to
or greater than the position threshold value, it is preferable that
a relative position of the blade with respect to the machine body
is maintained.
[0079] In this mode, since an increase in a blade load is
suppressed, generation of waviness of an execution surface can be
restrained. Specifically, the control is conducted in the following
manner. In this mode, an intermediate load region, where a blade
load is greater than the first load threshold value and smaller
than the second load threshold value, is a region to which a
moderate load is applied to the blade. In a case where the position
deviation is equal to or greater than the position threshold value
(first position threshold value), specifically, where a deviation
between a blade position and a target design surface is large, when
control to make the position deviation approach zero is conducted,
the blade enters into the ground so deeply that a possibility of an
increase in a blade load from a moderate load to a load equal to or
greater than the second load threshold value is increased. When the
blade load becomes equal to or greater than the second load
threshold value, control to raise the blade is conducted
irrespective of the position deviation. Such rise of the blade
position causes generation of waviness (heave) of an execution
surface. Accordingly, in the present mode, in a case where the
position deviation is equal to or greater than the position
threshold value (first position threshold value) in the
intermediate load region having a moderate load state, the blade
operation control part refrains from conducting such control to
change a relative position of the blade with respect to the machine
body, so that the relative position is maintained. This control
suppresses an increase in the blade load to thereby suppress
generation of waviness of the execution surface.
[0080] In the blade control device, in a case where the blade load
is greater than the first load threshold value and smaller than the
second load threshold value, and the position deviation is smaller
than the position threshold value, the blade operation control part
may control operation of the blade such that the position deviation
approaches zero.
[0081] In this mode, in a case where the position deviation is
smaller than the position threshold value (first position threshold
value) in the intermediate load region, the blade operation control
part conducts the control to make the blade position approach the
target design surface. This control improves work execution
efficiency. Specifically, the control is conducted in the following
manner. In a case where the position deviation is smaller than the
position threshold value (first position threshold value),
specifically, in a case where a deviation between the blade
position and the target design surface is small, even when the
control to make the position deviation approach zero is conducted,
because the blade position is close to the target design surface, a
possibility that the blade enters into the ground deeply and a
possibility of an increase in a blade load to become equal to or
greater than the second load threshold value are low. Accordingly,
in the present mode, in such a case, the blade operation control
part conducts the control to make the blade position approach the
target design surface. Since the control enables an execution
surface for a blade to quickly approach the target design surface,
work execution efficiency is improved.
[0082] The blade control device may be configured such that the
position threshold value is a first position threshold value, the
storage part further stores a second position threshold value which
is a threshold value of the position deviation and is smaller than
the first position threshold value, and the blade operation control
part controls operation of the blade such that the blade is raised
to make the position deviation approach zero in a case where the
blade load is equal to or less than the first load threshold value
and the position deviation is equal to or less than the second
position threshold value.
[0083] In this mode, since the control to raise the blade when the
position deviation becomes equal to or less than the second
position threshold value is conducted, it is possible to suppress
excessive digging due to falling of the blade below the target
design surface.
* * * * *