U.S. patent application number 16/475160 was filed with the patent office on 2019-11-07 for work vehicle and method of controlling work vehicle.
This patent application is currently assigned to KOMATSU LTD.. The applicant listed for this patent is KOMATSU LTD.. Invention is credited to Muneo HARADA, Yutaka ONO.
Application Number | 20190338495 16/475160 |
Document ID | / |
Family ID | 63107384 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190338495 |
Kind Code |
A1 |
HARADA; Muneo ; et
al. |
November 7, 2019 |
WORK VEHICLE AND METHOD OF CONTROLLING WORK VEHICLE
Abstract
A first switch valve is connected to a cap-side circuit of a
lift cylinder. A second switch valve is connected to a head-side
circuit of the lift cylinder. A first accumulator is connected to
the cap-side circuit of the lift cylinder with the first switch
valve being interposed. A second accumulator is connected to the
head-side circuit of the lift cylinder with the second switch valve
being interposed. A third switch valve is connected between the
first accumulator and the second accumulator.
Inventors: |
HARADA; Muneo; (Minato-ku,
Tokyo, JP) ; ONO; Yutaka; (Minato-ku, Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOMATSU LTD. |
Minato-ku, Tokyo |
|
JP |
|
|
Assignee: |
KOMATSU LTD.
Minato-ku, Tokyo
JP
|
Family ID: |
63107384 |
Appl. No.: |
16/475160 |
Filed: |
January 26, 2018 |
PCT Filed: |
January 26, 2018 |
PCT NO: |
PCT/JP2018/002483 |
371 Date: |
July 1, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/2267 20130101;
E02F 3/844 20130101; E02F 3/815 20130101; E02F 9/2228 20130101;
E02F 9/2285 20130101; E02F 9/2217 20130101; E02F 3/7636
20130101 |
International
Class: |
E02F 9/22 20060101
E02F009/22; E02F 3/815 20060101 E02F003/815 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2017 |
JP |
2017-023854 |
Claims
1. A work vehicle comprising: a work implement; a cylinder which
drives the work implement; a first switch valve connected to a
cap-side circuit of the cylinder; a second switch valve connected
to a head-side circuit of the cylinder; a first accumulator
connected to the cap-side circuit of the cylinder with the first
switch valve being interposed; a second accumulator connected to
the head-side circuit of the cylinder with the second switch valve
being interposed; and a third switch valve connected between the
first accumulator and the second accumulator.
2. The work vehicle according to claim 1, the work vehicle further
comprising a controller configured to control the first switch
valve, the second switch valve, and the third switch valve such
that the first switch valve is open and the second switch valve and
the third switch valve are closed in a shock absorption mode of the
work implement and such that the first switch valve is closed and
the second switch valve and the third switch valve are open in a
vibration suppression mode of the work vehicle.
3. The work vehicle according to claim 1, the work vehicle further
comprising a manual switch which allows selection between a state
that the first switch valve is open and the second switch valve and
the third switch valve are closed and a state that the first switch
valve is closed and the second switch valve and the third switch
valve are open.
4. The work vehicle according to claim 1, the work vehicle further
comprising a front wheel and a rear wheel, wherein the work
implement is arranged between the front wheel and the rear
wheel.
5. The work vehicle according to claim 4, wherein the work
implement is at least one of a blade and a scarifier.
6. The work vehicle according to claim 1, the work vehicle further
comprising a front wheel and a rear wheel, wherein the work
implement is arranged at least one of a position in front of the
front wheel and a position in rear of the rear wheel.
7. The work vehicle according to claim 6, wherein the work
implement is at least one of a front blade and a ripper.
8. The work vehicle according to claim 1, the work vehicle being a
grader.
9. A method of controlling a work vehicle, the work vehicle
including a work implement, a cylinder which drives the work
implement, a first switch valve connected to a cap-side circuit of
the cylinder, a second switch valve connected to a head-side
circuit of the cylinder, a first accumulator connected to the
cap-side circuit of the cylinder with the first switch valve being
interposed, a second accumulator connected to the head-side circuit
of the cylinder with the second switch valve being interposed, and
a third switch valve connected between the first accumulator and
the second accumulator, the method comprising: controlling the
first switch valve to open and controlling the second switch valve
and the third switch valve to close in a shock absorption mode of
the work implement and controlling the first switch valve to close
and controlling the second switch valve and the third switch valve
to open in a vibration suppression mode of the work vehicle.
Description
TECHNICAL FIELD
[0001] The present invention relates to a work vehicle and a method
of controlling a work vehicle.
BACKGROUND ART
[0002] A motor grader does not have a suspension function in its
undercarriage in order to ensure working performance in such works
as land-grading works, road cutting works, and excavation works. In
addition, the motor grader includes hollow tires. Therefore, the
tires serve as a spring system and vibration occurs in a vehicular
body around a specific vehicle speed. When the vehicular body
vibrates, a vehicle speed should be lowered in order to avoid
vibration during travel.
[0003] For example, Japanese Utility Model Laying-Open No. 2-132754
discloses a technique for suppressing vibration. A motor grader in
this literature includes a blade lift cylinder connected to a work
implement, a switch valve connected to a cap side of the blade lift
cylinder, a switch valve connected to a head side of the blade lift
cylinder, and an accumulator connected to the two switch
valves.
[0004] In the literature, when a head-side hydraulic circuit of the
blade lift cylinder and the accumulator communicate with each
other, vibration of the vehicular body during travel of the motor
grader is suppressed. Alternatively, when a cap-side hydraulic
circuit of the blade lift cylinder and the accumulator communicate
with each other, vertical impact on the work implement during works
by the motor grader is suppressed.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Utility Model Laying-Open No. 2-132754
SUMMARY OF INVENTION
Technical Problem
[0006] A capacity of an accumulator required for suppression of
vibration during travel, however, may be higher than a capacity of
the accumulator required for suppression of vertical impact on a
work implement. In this case, when the capacity of the accumulator
is adapted to the capacity required for suppression of vertical
impact on the work implement, the accumulator is unable to
sufficiently absorb vibration during travel.
[0007] On the other hand, when the capacity of the accumulator is
increased in order to sufficiently absorb vibration during travel,
force with which a blade (work implement) presses a road surface
during works becomes weaker. Then, desired road cutting capability
cannot be obtained.
[0008] An object of the present disclosure is to provide a work
vehicle capable of obtaining desired working capability while
sufficiently suppressing vibration during travel and a method of
controlling a work vehicle.
Solution to Problem
[0009] A work vehicle in the present disclosure includes a work
implement, a cylinder, a first switch valve, a second switch valve,
a first accumulator, a second accumulator, and a third switch
valve. The cylinder drives the work implement. The first switch
valve is connected to a cap-side circuit of the cylinder. The
second switch valve is connected to a head-side circuit of the
cylinder. The first accumulator is connected to the cap-side
circuit of the cylinder with the first switch valve being
interposed. The second accumulator is connected to the head-side
circuit of the cylinder with the second switch valve being
interposed. The third switch valve is connected between the first
accumulator and the second accumulator.
[0010] A method of controlling a work vehicle in the present
disclosure is a method of controlling the above-described work
vehicle, and includes controlling the first switch valve to open
and controlling the second switch valve and the third switch valve
to close in a shock absorption mode of the work implement and
controlling the first switch valve to close and controlling the
second switch valve and the third switch valve to open in a
vibration suppression mode of the work vehicle.
Advantageous Effects of Invention
[0011] According to the present disclosure, a work vehicle capable
of obtaining desired working capability while sufficiently
suppressing vibration during travel and a method of controlling a
work vehicle can be realized.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a perspective view schematically showing a
construction of a motor grader in one embodiment.
[0013] FIG. 2 is a side view schematically showing the construction
of the motor grader in one embodiment.
[0014] FIG. 3 is a schematic diagram showing a construction in
Comparative Example 1.
[0015] FIG. 4 is a schematic diagram showing a construction in
Comparative Example 2.
[0016] FIG. 5 is a side view of a motor grader showing other
exemplary work implements included in the motor grader in one
embodiment.
DESCRIPTION OF EMBODIMENTS
[0017] A work vehicle according to an embodiment of the present
disclosure will be described below with reference to the drawings.
The same elements have the same reference characters allotted in
the description below and their labels and functions are also the
same. Therefore, detailed description thereof will not be
repeated.
[0018] A construction of a motor grader representing one example of
a work vehicle to which the concept of the present disclosure is
applicable will initially be described.
[0019] FIG. 1 is a perspective view schematically showing a
construction of a motor grader in one embodiment of the present
disclosure. FIG. 2 is a side view schematically showing the
construction of the motor grader in one embodiment of the present
disclosure.
[0020] As shown in FIGS. 1 and 2, a motor grader 1 in the present
embodiment mainly includes running wheels 11 and 12, a vehicular
body frame 2, a cab 3, and a work implement 4. Motor grader 1
includes components such as an engine arranged in an engine
compartment 6. Work implement 4 includes, for example, a blade 42.
Motor grader 1 can do such works as land-grading works, road
cutting works, excavation works, snow removal works, and mixing of
materials with blade 42.
[0021] Running wheels 11 and 12 include a front wheel 11 and a rear
wheel 12. Though FIGS. 1 and 2 show running wheels six in total
which consist of two front wheels 11 one on each side and four rear
wheels 12 two on each side, the number of front wheels 11 and rear
wheels 12 and arrangement thereof are not limited to the example
shown in FIGS. 1 and 2.
[0022] In the description of the drawings below, a direction in
which motor grader 1 travels in straight lines is referred to as a
fore/aft direction of motor grader 1. In the fore/aft direction of
motor grader 1, a side where front wheel 11 is arranged with
respect to work implement 4 is defined as the fore direction. In
the fore/aft direction of motor grader 1, a side where rear wheel
12 is arranged with respect to work implement 4 is defined as the
aft direction. A lateral direction of motor grader 1 is a direction
orthogonal to the fore/aft direction in a plan view. A right side
and a left side in the lateral direction in facing front are
defined as a right direction and a left direction, respectively. An
upward/downward direction of motor grader 1 is a direction
orthogonal to the plane defined by the fore/aft direction and the
lateral direction. A side in the upward/downward direction where
the ground is located is defined as a lower side and a side where
the sky is located is defined as an upper side.
[0023] Vehicular body frame 2 extends in the fore/aft direction
(the lateral direction in FIG. 2). Vehicular body frame 2 includes
a front end 2F in a foremost portion and a rear end 2R in a
rearmost portion. Vehicular body frame 2 includes a rear frame 21
and a front frame 22.
[0024] Rear frame 21 supports components such as an engine arranged
in engine compartment 6. For example, each of four rear wheels 12
is attached to rear frame 21 and can rotatably be driven by driving
force from the engine.
[0025] Front frame 22 is attached in front of rear frame 21. Front
frame 22 is pivotably coupled to rear frame 21. Front frame 22
extends in the fore/aft direction. Front frame 22 includes a base
end portion coupled to rear frame 21 and a tip end portion opposite
to the base end portion. The base end portion of front frame 22 is
coupled to the tip end portion of rear frame 21 with a vertically
extending central pin being interposed.
[0026] An articulation cylinder 23 is attached between front frame
22 and rear frame 21. Front frame 22 is provided as being pivotable
with respect to rear frame 21 owing to extending and retracting of
articulation cylinder 23.
[0027] For example, two front wheels 11 are rotatably attached to
the tip end portion of front frame 22. Front wheel 11 is attached
to front frame 22 as being revolvable owing to extending and
retracting of a steering cylinder 7. Motor grader 1 can change its
direction of travel owing to extending and retracting of steering
cylinder 7.
[0028] Front wheel 11 is attached to front frame 22 without a
suspension being interposed. Rear wheel 12 is attached to rear
frame 21 without a suspension being interposed. The suspension here
means a component constituted of a suspension arm, a spring, and a
shock absorber, and does not include elastic force of a tire.
[0029] A counter weight 51 is attached to front end 2F of vehicular
body frame 2. Counter weight 51 represents one type of attachments
to be attached to front frame 22. Counter weight 51 is attached to
front frame 22 in order to increase a downward load to be applied
to front wheel 11 to allow steering and to increase a pressing load
on blade 42.
[0030] Cab 3 is carried on front frame 22. In cab 3, an operation
portion (not shown) such as a steering wheel, a gear shift lever, a
lever for controlling work implement 4, a brake, an accelerator
pedal, and an inching pedal is provided. Cab 3 may be carried on
rear frame 21.
[0031] Work implement 4 mainly includes, for example, a draw bar 40
and blade 42. Draw bar 40 is arranged below front frame 22. Draw
bar 40 has a front end portion coupled to the tip end portion of
front frame 22 with a ball bearing portion. Draw bar 40 has the
front end portion swingably attached to the tip end portion of
front frame 22.
[0032] Draw bar 40 has a rear end portion supported on front frame
22 by lift cylinders 44 and 45. Owing to extending and retracting
of lift cylinders 44 and 45, the rear end portion of draw bar 40
can move up and down with respect to front frame 22. Draw bar 40 is
vertically swingable with an axis along a direction of travel of
the vehicle being defined as the center, as a result of extending
and retracting of lift cylinders 44 and 45.
[0033] Blade 42 is arranged between front wheel 11 and rear wheel
12. Front wheel 11 is arranged in front of blade 42. Rear wheel 12
is arranged in the rear of blade 42. Blade 42 is arranged between
front end 2F of vehicular body frame 2 and rear end 2R of vehicular
body frame 2. Blade 42 is supported on draw bar 40. Blade 42 is
supported on front frame 22 with draw bar 40 being interposed.
[0034] As set forth above, blade 42 is constructed to be able to
move up and down with respect to the vehicle with draw bar 40 being
interposed.
[0035] A shock absorption and vibration suppression mechanism which
absorbs vertical impact on a work implement during works and
suppresses vibration of a vehicular body during travel in the
present embodiment will now be described with reference to FIG.
2.
[0036] As shown in FIG. 2, a shock absorption and vibration
suppression mechanism 70 mainly includes a first switch valve 71a,
a second switch valve 71b, a third switch valve 71c, a fourth
switch valve 71d, a first accumulator 72a, a second accumulator
72b, a controller 74, and a switch 75.
[0037] First switch valve 71a is connected to a cap-side circuit of
lift cylinder 44. Second switch valve 71b is connected to a
head-side circuit of lift cylinder 44. First accumulator 72a is
connected to the cap-side circuit of lift cylinder 44 with first
switch valve 71a being interposed. Second accumulator 72b is
connected to the head-side circuit of lift cylinder 44 with second
switch valve 71b being interposed. Third switch valve 71c is
connected between first accumulator 72a and second accumulator
72b.
[0038] A main valve 73 is connected to the cap-side circuit of lift
cylinder 44 through an oil path 81a. Main valve 73 is connected to
the head-side circuit of lift cylinder 44 through an oil path 81b.
First switch valve 71a is connected to an oil path 82abranched from
oil path 81a. Second switch valve 71b is connected to an oil path
82b branched from oil path 81b.
[0039] First switch valve 71a and third switch valve 71c are
connected to each other through an oil path 83. First accumulator
72a is connected to oil path 83. Second switch valve 71b and third
switch valve 71c are connected to each other through an oil path
84. Second accumulator 72b is connected to oil path 84.
[0040] Fourth switch valve 71d is connected to the cap-side circuit
of lift cylinder 44. Fourth switch valve 71d is connected to the
cap-side circuit of lift cylinder 44 through an oil path 82c
branched from oil path 81a. Fourth switch valve 71d is connected to
an oil tank 90 through an oil path 85.
[0041] Each of first to fourth switch valves 71a to 71d is
electrically connected, for example, to controller 74. Each of
first to fourth switch valves 71a to 71d performs an opening and
closing operation, for example, based on a control signal from
controller 74.
[0042] While first switch valve 71a is open, first accumulator 72a
is connected to the cap-side circuit of lift cylinder 44.
Alternatively, while first switch valve 71a is closed, first
accumulator 72a and the cap-side circuit of lift cylinder 44 are
disconnected from each other.
[0043] While first switch valve 71a is open and third switch valve
71c is open, both of first accumulator 72a and second accumulator
72b are connected to the cap-side circuit of lift cylinder 44.
Alternatively, while first switch valve 71a is open and third
switch valve 71c is closed, first accumulator 72a is connected to
the cap-side circuit of lift cylinder 44 whereas second accumulator
72b and the cap-side circuit of lift cylinder 44 are disconnected
from each other.
[0044] While second switch valve 71b is open, second accumulator
72b is connected to the head-side circuit of lift cylinder 44.
Alternatively, while second switch valve 71b is closed, second
accumulator 72b and the head-side circuit of lift cylinder 44 are
disconnected from each other.
[0045] While second switch valve 71b is open and third switch valve
71c is open, both of second accumulator 72b and first accumulator
72a are connected to the head-side circuit of lift cylinder 44.
Alternatively, while second switch valve 71b is open and third
switch valve 71c is closed, second accumulator 72b is connected to
the head-side circuit of lift cylinder 44 whereas first accumulator
72a and the head-side circuit of lift cylinder 44 are disconnected
from each other.
[0046] Shock absorption and vibration suppression mechanism 70 is
controlled, for example, to open first switch valve 71a and close
second switch valve 71b and third switch valve 71c in a shock
absorption mode of work implement 4. Alternatively, shock
absorption and vibration suppression mechanism 70 is controlled,
for example, to close first switch valve 71a and open second switch
valve 71b and third switch valve 71c in a vibration suppression
mode of motor grader 1.
[0047] Switching between the shock absorption mode and the
vibration suppression mode may be made by controller 74.
Specifically, for example, controller 74 controls first switch
valve 71a to open and controls second switch valve 71b and third
switch valve 71c to close in the shock absorption mode of work
implement 4. Alternatively, for example, controller 74 controls
first switch valve 71a to close and controls second switch valve
71b and third switch valve 71c to open in the vibration suppression
mode of motor grader 1.
[0048] Alternatively, switching between the shock absorption mode
and the vibration suppression mode may be made by switch 75. Switch
75 is implemented, for example, by a manual switch operated
manually by an operator. When the operator operates switch 75 to
select the shock absorption mode, for example, first switch valve
71a is opened and second switch valve 71b and third switch valve
71c are closed. Alternatively, when the operator operates switch 75
to select the vibration suppression mode, for example, first switch
valve 71a is closed and second switch valve 71b and third switch
valve 71c are opened.
[0049] Each of first to fourth switch valves 71a to 71d may perform
the opening and closing operation upon directly receiving a signal
from switch 75. Alternatively, each of first to fourth switch
valves 71a to 71d may perform the opening and closing operation
upon receiving a command from controller 74 which has received a
signal from switch 75.
[0050] Alternatively, each of first to fourth switch valves 71a to
71d may perform the opening and closing operation upon receiving a
command from controller 74, regardless of an operation of switch
75. In this case, controller 74 may send a command to each of first
to fourth switch valves 71a to 71d based on a signal of at least
one of a speed of the work vehicle and a speed stage of a
transmission. For example, when the speed stage is set to F6, F7,
or F8 or when a vehicle speed attains to 35 km/h or higher,
controller 74 may make switching from the shock absorption mode to
the vibration suppression mode.
[0051] First shock absorption and vibration suppression mechanism
70 may be connected to lift cylinder 44 shown in FIG. 1 and second
shock absorption and vibration suppression mechanism 70 constructed
similarly to first shock absorption and vibration suppression
mechanism 70 may be connected to lift cylinder 45. Alternatively, a
connection portion 70C of single shock absorption and vibration
suppression mechanism 70 shown in FIG. 2 may be connected to the
cap-side circuit of each of lift cylinders 44 and 45 and a
connection portion 70H may be connected to the head-side circuit of
each of lift cylinders 44 and 45.
[0052] As shown in FIG. 1, each of first accumulator 72a and second
accumulator 72b is attached, for example, to a side portion of
front frame 22.
[0053] A method of controlling a work vehicle in the present
embodiment will now be described with reference to FIG. 2.
[0054] As shown in FIG. 2, initially, during normal works, each of
first to third switch valves 71a, 71b, and 71c is closed. In this
state, hydraulic oil is supplied from main valve 73 to lift
cylinder 44. Work implement 4 thus moves up and down to perform
works.
[0055] The shock absorption mode of work implement 4 is used, for
example, when works are performed with blade 42 being engaged with
the ground. In the shock absorption mode, first switch valve 71a is
opened and second switch valve 71b and third switch valve 71c are
closed. As first switch valve 71a is opened, oil path 82a and oil
path 83 are connected to each other. First accumulator 72a is thus
connected to the cap-side circuit of lift cylinder 44.
[0056] Since second switch valve 71b is closed, oil path 82b and
oil path 84 are disconnected from each other. Second accumulator
72b and the head-side circuit of lift cylinder 44 are thus
disconnected from each other. Since third switch valve 71c is
closed, oil path 84 and oil path 83 are disconnected from each
other. First accumulator 72a and the head-side circuit of lift
cylinder 44 are thus also disconnected from each other.
[0057] As set forth above, in the shock absorption mode, first
accumulator 72a is connected to the cap-side circuit of lift
cylinder 44. Therefore, when blade 42 receives shock by colliding
with a projection on a road surface such as a rock during works, an
air chamber (a space surrounded by a diaphragm) of first
accumulator 72a contracts. Shock to work implement 42 is thus
absorbed by first accumulator 72a.
[0058] The vibration suppression mode of motor grader 1 is used,
for example, while motor grader 1 is traveling and blade 42 is
lifted above the ground without being engaged with the ground. In
the vibration suppression mode, first switch valve 71a is closed
and second switch valve 71b and third switch valve 71c are opened.
As first switch valve 71a is closed, oil path 82a and oil path 83
are disconnected from each other. First accumulator 72a and the
cap-side circuit of lift cylinder 44 are thus disconnected from
each other.
[0059] Since second switch valve 71b is opened, oil path 82b and
oil path 84 are connected to each other. Second accumulator 72b is
thus connected to the head-side circuit of lift cylinder 44. Since
third switch valve 71c is opened, oil path 84 and oil path 83 are
connected to each other. First accumulator 72a is thus also
connected to the head-side circuit of lift cylinder 44.
[0060] As set forth above, in the vibration suppression mode, both
of first accumulator 72a and second accumulator 72b are connected
to the head-side circuit of lift cylinder 44. Therefore, work
implement 42 is vertically movably held. At this time, a dynamic
vibration absorber having a spring effect of each of first
accumulator 72a and second accumulator 72b and a damping effect
originating from throttling of a hydraulic circuit is implemented
and vibration of the vehicular body is suppressed.
[0061] A function and effect of the present embodiment will now be
described in comparison to Comparative Example 1 shown in FIG. 3
and Comparative Example 2 shown in FIG. 4.
[0062] As shown in FIG. 3, a construction of a shock absorption and
vibration suppression mechanism 70a in Comparative Example 1 is
different from the construction in FIG. 2 in that third switch
valve 71c and second accumulator 72b are not provided. Therefore,
accumulator 72a is connected to second switch valve 71b through an
oil path 86.
[0063] Since the construction of Comparative Example 1 is otherwise
substantially the same as the construction shown in FIG. 2,
elements identical to those in the construction shown in FIG. 2
have the same reference characters allotted and description thereof
will not be repeated.
[0064] In Comparative Example 1 shown in FIG. 3, in the shock
absorption mode, first switch valve 71a is opened and second switch
valve 71b is closed so that accumulator 72a can be connected to the
cap-side circuit of lift cylinder 44. Alternatively, in the
vibration suppression mode, first switch valve 71a is closed and
second switch valve 71b is opened so that accumulator 72a can be
connected to the head-side circuit of lift cylinder 44.
[0065] In Comparative Example 1, one accumulator 72a is shared
between the shock absorption mode and the vibration suppression
mode. Therefore, when a capacity required in the vibration
suppression mode is higher than a capacity required in the shock
absorption mode, accumulator 72a is unable to sufficiently absorb
vibration during travel.
[0066] Increase in capacity of accumulator 72a may be possible as a
method of overcoming this problem. In this case, however, force
with which work implement 42 presses a road surface during works
becomes weaker and desired road cutting capability is not
obtained.
[0067] It is also possible, as the method of overcoming the
problem, to individually provide accumulator 72a for absorbing
shock and accumulator 72b for suppressing vibration as in a shock
absorption and vibration suppression mechanism 70b in Comparative
Example 2 shown in FIG. 4. According to this construction, a
capacity of accumulator 72a for absorbing shock can be set to a
capacity required in the shock absorption mode and a capacity of
accumulator 72b for suppressing vibration can be set to a capacity
required in the vibration suppression mode.
[0068] In this case, however, two accumulators 72a and 72b high in
capacity are required, which leads to increase in size of an
apparatus. When each of two accumulators 72a and 72b high in
capacity is attached to the side portion of front frame 22 as shown
in FIG. 1, front visibility of an operator becomes poor.
[0069] In contrast, as shown in FIG. 2, motor grader 1 in the
present embodiment includes first and second accumulators 72a and
72b and first to third switch valves 71a to 71c. Thus, in one of
the shock absorption mode and the vibration suppression mode, both
of first and second accumulators 72a and 72b can absorb shock or
suppress vibration. In the other of the shock absorption mode and
the vibration suppression mode, any one of first and second
accumulators 72a and 72b alone can absorb shock or suppress
vibration.
[0070] Thus, in a mode requiring a relatively low capacity of the
accumulator, any one of first and second accumulators 72a and 72b
alone can be used. In a mode requiring a relatively high capacity
of the accumulator, both of first and second accumulators 72a and
72b can be used.
[0071] A capacity of the accumulator in accordance with each of the
two modes can thus be obtained. Therefore, vibration during travel
can sufficiently be absorbed in the vibration suppression mode and
force with which work implement 42 presses a road surface can also
sufficiently be obtained in the shock absorption mode.
[0072] In a mode requiring a relatively high accumulator capacity,
both of first and second accumulators 72a and 72b are used.
Therefore, only a single accumulator alone does not have to fulfill
the relatively high accumulator capacity as in Comparative Example
2. Accordingly, each of first and second accumulators 72a and 72b
can be smaller in size than an accumulator in an example in which
only a single accumulator alone fulfills a relatively high
accumulator capacity. Increase in size of an apparatus can thus be
suppressed. Even when each of first and second accumulators 72a and
72b is attached to the side portion of front frame 22, a front
field of view of an operator can satisfactorily be kept.
[0073] In the present embodiment, controller 74 controls first to
third switch valves 71a to 71c such that first switch valve 71a is
open and second and third switch valves 71b and 71c are closed in
the shock absorption mode and such that first switch valve 71a is
closed and second and third switch valves 71b and 71c are open in
the vibration suppression mode.
[0074] Thus, even when a capacity of an accumulator required in the
vibration suppression mode is higher than a capacity of an
accumulator required in the shock absorption mode, a capacity of
the accumulator suitable for both modes can be obtained.
[0075] Specifically, in the shock absorption mode, only first
accumulator 72a is connected to the cap-side circuit of lift
cylinder 44. Therefore, shock can appropriately be absorbed by
first accumulator 72a. In the vibration suppression mode, first and
second accumulators 72a and 72b are connected to the head-side
circuit of lift cylinder 44. Therefore, even when a capacity of the
accumulator required for suppression of vibration is higher than a
capacity of the accumulator required for absorption of shock, a
total capacity of first and second accumulators 72a and 72b can
address such a situation. Therefore, vibration of the vehicular
body during travel can sufficiently be suppressed.
[0076] In the present embodiment, selection between the shock
absorption mode and the vibration suppression mode may be made by a
manual operation of switch 75. Specifically, by manually operating
switch 75, selection between a state that first switch valve 71a is
open and second and third switch valves 71b and 71c are closed and
a state that first switch valve 71a is closed and second and third
switch valves 71b and 71c are open may be made.
[0077] Thus, selection between the shock absorption mode and the
vibration suppression mode can be made by an operation by an
operator.
[0078] Though blade 42 is described above as a work implement to
which shock absorption and vibration suppression mechanism 70 is
applied, a work implement to which shock absorption and vibration
suppression mechanism 70 is applied should only be a work implement
arranged between front wheel 11 and rear wheel 12.
[0079] Specifically, as shown in FIG. 5, a work implement to which
shock absorption and vibration suppression mechanism 70 is applied
may be at least one of blade 42 and a scarifier 9. Scarifier 9 is
supported on front frame 22 with a hydraulic cylinder 9a being
interposed. Hydraulic cylinder 9a allows scarifier 9 to move up and
down with respect to front frame 22.
[0080] When shock absorption and vibration suppression mechanism 70
is applied to scarifier 9, connection portion 70C of oil path 81a
of shock absorption and vibration suppression mechanism 70 shown in
FIG. 2 is connected to the cap-side circuit of hydraulic cylinder
9a. Connection portion 70H of oil path 81b of shock absorption and
vibration suppression mechanism 70 shown in FIG. 2 is connected to
the head-side circuit of hydraulic cylinder 9a.
[0081] As shock absorption and vibration suppression mechanism 70
is applied to the work implement arranged between front wheel 11
and rear wheel 12 (for example, blade 42 or scarifier 9), bouncing
vibration of motor grader 1 can be suppressed.
[0082] A work implement to which shock absorption and vibration
suppression mechanism 70 is applied may be at least one of a work
implement arranged in front of front wheel 11 and a work implement
arranged in the rear of rear wheel 12.
[0083] Specifically, as shown in FIG. 5, a work implement to which
shock absorption and vibration suppression mechanism 70 is applied
may be at least one of a front blade 10 and a ripper 8. Front blade
10 is arranged in front of front wheel 11. Front blade 10 is
supported on front frame 22 with a hydraulic cylinder 10a being
interposed. Hydraulic cylinder 10a allows front blade 10 to move up
and down with respect to front frame 22.
[0084] When shock absorption and vibration suppression mechanism 70
is applied to front blade 10, connection portion 70C of oil path
81a of shock absorption and vibration suppression mechanism 70
shown in FIG. 2 is connected to the cap-side circuit of hydraulic
cylinder 10a. Connection portion 70H of oil path 81b of shock
absorption and vibration suppression mechanism 70 shown in FIG. 2
is connected to the head-side circuit of hydraulic cylinder
10a.
[0085] Ripper 8 is arranged in the rear of rear wheel 12. Ripper 8
is supported on rear frame 21 with a hydraulic cylinder 8a being
interposed. Hydraulic cylinder 8a allows ripper 8 to move up and
down with respect to rear frame 21.
[0086] When shock absorption and vibration suppression mechanism 70
is applied to ripper 8, connection portion 70C of oil path 81a of
shock absorption and vibration suppression mechanism 70 shown in
FIG. 2 is connected to the cap-side circuit of hydraulic cylinder
8a. Connection portion 70H of oil path 81b of shock absorption and
vibration suppression mechanism 70 shown in FIG. 2 is connected to
the head-side circuit of hydraulic cylinder 8a.
[0087] As shock absorption and vibration suppression mechanism 70
is applied to a work implement (for example, front blade 10)
arranged in front of front wheel 11 or a work implement (for
example, ripper 8) arranged in the rear of rear wheel 12, pitching
vibration of motor grader 1 can be suppressed.
[0088] First accumulator 72a and second accumulator 72b in FIG. 2
may be different from each other or identical to each other in
capacity. When first accumulator 72a is different in capacity from
second accumulator 72b, first accumulator 72a may be higher or
lower in capacity than second accumulator 72b.
[0089] A capacity of an accumulator required in the shock
absorption mode may be higher than a capacity of an accumulator
required in the vibration suppression mode. In the shock absorption
mode in this case, controller 74 controls first switch valve 71a
and third switch valve 71c to open and controls second switch valve
71b to close in FIG. 2. In the vibration suppression mode in this
case, controller 74 controls first switch valve 71a and third
switch valve 71c to close and controls second switch valve 71b to
open.
[0090] Controller 74 in FIG. 2 controls the switch valves such that
only any one of first accumulator 72a and second accumulator 72b is
connected to a first circuit of the cap-side circuit and the
head-side circuit of work implement hydraulic cylinder 44, 8a, 9a,
or 10a in a first mode requiring a relatively low accumulator
capacity of the shock absorption mode and the vibration suppression
mode. Alternatively, controller 74 controls the switch valves such
that both of first accumulator 72a and second accumulator 72b are
connected to a second circuit of the cap-side circuit and the
head-side circuit of work implement hydraulic cylinder 44, 8a, 9a,
or 10a in a second mode requiring a relatively high accumulator
capacity of the shock absorption mode and the vibration suppression
mode.
[0091] It should be understood that the embodiment disclosed herein
is illustrative and non-restrictive in every respect. The scope of
the present invention is defined by the terms of the claims rather
than the description above and is intended to include any
modifications within the scope and meaning equivalent to the terms
of the claims.
REFERENCE SIGNS LIST
[0092] 1 motor grader (work vehicle); 2 vehicular body frame; 2F
front end; 2R rear end; 3 cab; 4 work implement; 6 engine
compartment; 7 steering cylinder; 8 ripper; 8a, 9a, 10a hydraulic
cylinder; 9 scarifier; 10 front blade; 11 front wheel; 12 rear
wheel; 21 rear frame; 22 front frame; 23 articulation cylinder; 40
draw bar; 42 blade; 44, 45 lift cylinder; 51 counter weight; 70
shock suppression mechanism; 70C, 70H connection portion; 71a first
switch valve; 71b second switch valve; 71c third switch valve; 71d
fourth switch valve; 72a first accumulator; 72b second accumulator;
73 main valve; 74 controller; 75 switch; 81a, 81b, 82a, 82b, 82c,
83, 84, 85, 86 oil path; and 90 oil tank
* * * * *