U.S. patent application number 15/409571 was filed with the patent office on 2017-09-14 for transportation vehicle.
The applicant listed for this patent is Hitachi Construction Machinery Co., Ltd.. Invention is credited to Toshikazu MINOSHIMA, Akira OHNO, Hirokazu SHIMOMURA.
Application Number | 20170259721 15/409571 |
Document ID | / |
Family ID | 57906442 |
Filed Date | 2017-09-14 |
United States Patent
Application |
20170259721 |
Kind Code |
A1 |
OHNO; Akira ; et
al. |
September 14, 2017 |
TRANSPORTATION VEHICLE
Abstract
An object is to restrain a hoist shaft and a bushing of a hoist
cylinder from abrading. A haulage vehicle with a pivoting vessel
has a telescoping hoist cylinder provided between the vessel and
the vehicle. Supply of hydraulic oil to the hoist cylinder is
controlled by a valve provided between the hydraulic power source
and the hoist cylinder. The haulage vehicle is provided with a
bushing at one end portion of the hoist cylinder; a hoist shaft is
mounted in a through bore of the bushing; a lubricant supplier
supplies lubricant to a clearance between a surface of the hoist
shaft and an internal surface of the through bore of the bushing;
and when the vessel is seated on the vehicle, a controller controls
the valve to make the hoist cylinder contract and also supply
lubricant to the clearance.
Inventors: |
OHNO; Akira; (Tsuchiura-shi,
JP) ; SHIMOMURA; Hirokazu; (Tsuchiura-shi, JP)
; MINOSHIMA; Toshikazu; (Ushiku-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi Construction Machinery Co., Ltd. |
Tokyo |
|
JP |
|
|
Family ID: |
57906442 |
Appl. No.: |
15/409571 |
Filed: |
January 19, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60P 1/16 20130101; B60P
1/22 20130101; B60P 1/162 20130101 |
International
Class: |
B60P 1/22 20060101
B60P001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2016 |
JP |
2016-050300 |
Claims
1. A haulage vehicle having a vessel pivotably provided relative to
a vehicle, a hoist cylinder provided telescopically between the
vessel and the vehicle, a hydraulic power source that supplies the
host cylinder with hydraulic oil, and a valve provided between the
hydraulic power source and the hoist cylinder for controlling the
flow of hydraulic oil supplied to the hoist cylinder, the haulage
vehicle comprising: a bushing provided at one end portion of the
hoist cylinder; a hoist shaft provided in the vehicle and mounted
in a through bore of the bushing; a lubricant supplier that
supplies lubricant to a clearance between a surface of the hoist
shaft and an internal surface of the through bore of the bushing; a
seating detection device that detects whether the vessel is seated
on the vehicle or not; and a controller that when the vessel is
seated on the vehicle, controls the valve to make the hoist
cylinder contract and also controls the lubricant supplier to
supply lubricant to the clearance.
2. The haulage vehicle according to claim 1, wherein the controller
is provided with: a seating judgment section for judging that the
vessel has proceeded from a non-seated state of the vessel being
not seated on the vehicle to a seated state of the vessel being
seated on the vehicle; and a lubricant supply control section that
when a movement from the non-seated state to the seated state is
judged by the seating judgment section, controls the valve to make
the hoist cylinder contract and then controls the lubricant
supplier to supply lubricant to the clearance.
3. The haulage vehicle according to claim 1, wherein the controller
is provided with a lubricant supply control section that each time
a predetermined period of time elapses with the vessel seated on
the vehicle, controls the valve to make the hoist cylinder contract
and then controls the lubricant supplier to supply lubricant to the
clearance.
4. The haulage vehicle according to claim 1, wherein: the valve has
a plurality of switching positions including a rise position in
which the hoist cylinder is extended through the supply and
discharge of hydraulic oil to lift up the vessel, a fall position
in which the hoist cylinder is made to contract through the supply
and discharge of hydraulic oil to pivotally move the vessel
downward, a floating position in which the vessel is allowed to
fall by its gravity, and a hold position in which the movement of
the hoist cylinder is discontinued by stopping the supply and
discharge of hydraulic oil; and the controller is provided with a
valve control section that switches the switching position of the
valve to the floating position after the lubricant supplier
supplies lubricant to the clearance.
5. The haulage vehicle according to claim 1, wherein the bushing is
a cylindrical member, and is provided with: a groove that is
provided on a surface of the bushing in the circumferential
direction for leading the lubricant supplied from the lubricant
supplier; and a hole provided in the groove for leading the
lubricant supplied to the groove to the clearance.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The present invention relates to a haulage vehicle.
[0003] 2. Description of the Related Art
[0004] There has been known a dump truck with a vessel provided to
be able to rise and fall on a vehicle. The dump truck transports a
large amount of transportation objects such as crushed rocks,
earth, sand and so on loaded in the vessel. The dump truck is
provided with a hoist cylinder that is telescopically provided
between the vessel and the vehicle and that extends to tilt the
vessel when discharging the transportation objects from the vessel,
as described in International Application Publication No.
WO2008/099691.
[0005] The hoist cylinder is connected at its lower end with a
hoist shaft provided in the vehicle and is connected at its upper
end with the vessel by means of a pin. The hoist cylinder has a rod
head disposed at its lower end, the rod head is provided with a
bore through which the hoist shaft passes, and a cylindrical
bushing is arranged in the bore.
[0006] The hoist shaft is mounted on the rod head through the
cylindrical bushing. The inside diameter of the bushing provided on
the rod head is set to be smaller slightly than the outside
diameter of the hoist shaft.
[0007] The hoist shaft supports the dead weight of those including
the vessel and the hoist cylinder. That is, the hoist shaft
supports the load directed downward (toward the ground under the
vehicle). In this state, a tight contact is held between an
internal surface upper part of the bushing and a surface upper part
of the hoist shaft, and this gives rise to a problem that it is
unable to supply lubricant to the tight contact portion between the
hoist shaft and the bushing and hence, that the upper parts of the
hoist shaft and the bushing abrade easier than other parts
thereof.
SUMMARY
[0008] In one aspect of the present invention, there is provided
with a haulage vehicle, which is provided with: a vessel pivotably
provided relative to a vehicle; a hoist cylinder provided
telescopically between the vessel and the vehicle; a hydraulic
power source that supplies the host cylinder with hydraulic oil;
and a valve provided between the hydraulic power source and the
hoist cylinder for controlling the flow of hydraulic oil supplied
to the hoist cylinder, wherein the haulage vehicle is further
provided with: a bushing provided at one end portion of the hoist
cylinder; a hoist shaft provided in the vehicle and mounted in a
through bore of the bushing; a lubricant supplier that supplies
lubricant to a clearance between a surface of the hoist shaft and
an internal surface of the through bore of the bushing; a seating
detection device that detects whether the vessel is seated on the
vehicle or not; and a controller that when the vessel is seated on
the vehicle, controls the valve to make the hoist cylinder contract
and also controls the lubricant supplier to supply lubricant to the
clearance.
[0009] According to the present invention, it is possible to
restrain the hoist shaft and the bushing of the hoist cylinder from
abrading, so that the hoist shaft and the bushing can be extended
in service life.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A non-limiting and non-exhaustive embodiment of the present
invention will be described with reference to the following
drawings, wherein like reference signs refer to like parts
throughout various views unless otherwise specified.
[0011] FIG. 1 is a side view of a dump truck according to one
embodiment of the present invention,
[0012] FIG. 2 is a side view of the dump truck with a vessel tilted
obliquely rearward,
[0013] FIG. 3 is a hydraulic circuit diagram for driving a hoist
cylinder,
[0014] FIG. 4 is a control block diagram for the dump truck,
[0015] FIG. 5 is a side view showing the configuration of a seating
sensor,
[0016] FIG. 6 is a circuit diagram showing a grease feed
device,
[0017] FIG. 7A is a schematic longitudinal-sectional view of a
connection portion between the hoist cylinder and the hoist shaft,
taken along an imaginary plane parallel to the axis of the hoist
shaft,
[0018] FIG. 7B is a fragmentary enlarged view of a portion C in
FIG. 7A,
[0019] FIG. 8 is a fragmentary cross-sectional view showing the
positional relation between a bushing and the hoist shaft in the
state that the vessel is seated on a vehicle and that a valve is
operated in a float position,
[0020] FIG. 9 is another fragmentary cross-sectional view showing
the positional relation between the bushing and the hoist shaft in
the state that the hoist cylinder is made to contract by a
predetermined amount from the state shown in FIG. 8, and
[0021] FIG. 10 is a flowchart showing the processing details of a
lubricant supply control by a controller according to the present
embodiment.
DETAILED DESCRIPTION
[0022] Hereafter, with reference to the drawings, one embodiment of
a haulage vehicle according to the present invention will be
described by taking as example a heavy-duty dump truck that
transports crushed rocks and the like mined in mines and the like.
FIG. 1 is a side view (as viewed from left side of the vehicle) of
a dump truck 1 according to one embodiment of the present
invention. FIG. 2 is a side view (as viewed from left side of the
vehicle) of the dump truck 1 with a vessel 3 tilted obliquely
rearward. For convenience in description, the front-rear direction
and the upper-lower (upward-downward) direction are prescribed as
indicated in these figures.
[0023] As shown in FIG. 1 and FIG. 2, the dump truck 1 is provided
with a self-propellable vehicle, the vessel 3 as a loading platform
that is provided to be able to rise and fall (i.e., to be
pivotable) on a vehicle frame 2 constituting the vehicle, a cab
(driver's cab) 6 provided at the front part of the vehicle frame 2,
and hoist cylinders 10 that pivotably move the vessel 3 (i.e., that
make the vessel 3 rise or fall) in the upward-downward
direction.
[0024] The vessel 3 is formed as, for example, a giant-sized
container of 10-13 meters long in entire length for loading thereon
a large amount of heavy transportation objects such as crushed
rocks and the like (hereafter referred to as crushed rocks 4). The
vessel 3 is integrally provided with a container section 3B for
containing the crushed rocks 4 and a canopy section 3A which is
provided at the front side of the container section 3B and which
covers the upper part of the cab 6 to protect the cab 6 from
scattering rocks.
[0025] A bottom part on the rear side of the vessel 3 is coupled
with the vehicle frame 2 to be pivotable (to be able to rise and
fall) relative to the vehicle frame 2 through a connecting pin 5
provided in the vicinity of the rear end of the vehicle frame 2.
When the hoist cylinders 10 expand or contract, the vessel 3 rises
or falls so that the canopy section 3A on the front side of the
vessel 3 pivots in the upward-downward about the connecting pin 5
serving as a fulcrum. The vessel 3 is pivoted between a
transportation position shown in FIG. 1 and a dumping position
shown in FIG. 2. When the hoist cylinders 10 expand to make the
vessel 3 pivot toward the dumping position, the crushed rocks 4
loaded in the vessel 3 are discharged to a predetermined
pickup/collection point as they slip down from the vessel 3 that is
tilted obliquely rearward to have the rear side positioned below
the front side as shown in FIG. 2. When being at the transportation
position as shown in FIG. 1, the vessel 3 is held in the seated
state with the bottom portion on the front side of the container
section 3B seated on a chassis table (not shown) of the vehicle
frame 2.
[0026] In the cab 6, there are provided a driver's seat on which an
operator is seated, a starter switch for starting an engine 9, an
acceleration pedal for causing the vehicle to travel, a brake pedal
for giving the vehicle a brake force, a steering handle for
steering operation (all not shown) and an operating lever device 28
(refer to FIG. 4) for making the vessel 3 to rise or fall.
[0027] The dump truck 1 is provided with front wheels 7 and rear
wheels 8. The front wheels 7 constitute steered wheels which are
steerable (can be given a steering operation) by the operator of
the dump truck 1. Between the front part of the vehicle frame 2 and
the front wheels 7, there are provided front wheel side suspensions
7A constituted by hydraulic shock absorbers, and the front part
side of the vehicle frame 2 is supported by the front wheel side
suspensions 7A.
[0028] The rear wheels 8 constitute drive wheels of the dump truck
1 and are rotationally driven by a traveling drive device (not
shown). Between the rear wheels 8 and the rear part of the vehicle
frame 2, there are provide rear wheel side suspensions 8A
constituted by hydraulic shock absorbers and the like, so that the
rear part side of the vehicle frame 2 is supported by the rear
wheel side suspensions 8A. The outside diameter of the front wheels
7 and the rear wheels 8 is up to the range of 2 to 4 meters.
[0029] Inside the vehicle frame 2 under the cab 6, the engine 9 is
provided as a prime mover. The engine 9 is constituted by, for
example, a large-sized diesel engine and the like.
[0030] Between the vehicle frame 2 and the vessel 3, a pair of the
hoist cylinders 10 (the hoist cylinder on the left side only is
shown in FIG. 1) are provided telescopically. Each hoist cylinder
10 is a hydraulic cylinder of a multistage type (e.g., a two-stage
type).
[0031] FIG. 3 shows a hydraulic circuit diagram for driving the
hoist cylinders 10. The hoist cylinders 10 are paired to have the
same configuration. As shown in FIG. 3, the hoist cylinders 10 are
each provided with a cylindrical outer tube portion 10A, a
cylindrical inner tube portion 10B provided telescopically inside
the outer tube portion 10A and partitioning the interior of the
outer tube portion 10A into an upper side oil chamber A and a lower
side oil chamber B, and a piston rod 10C provided telescopically in
the interior of the inner tube portion 10B. As mentioned, the pair
of the hoist cylinders 10 are identical in its configuration and
operation as well as in connection relation with the hydraulic
circuit shown in FIG. 3. Therefore, as a matter of convenience, the
following description will be directed typically to one only of the
hoist cylinders 10 unless otherwise specified to the contrary, and
such description directed to one hoist cylinder 10 will be equally
applied to the other hoist cylinder 10.
[0032] The hoist cylinder 10 extends the piston rod 10C when
supplied at the oil chamber A with hydraulic oil from the main pump
11 and when discharging hydraulic oil from the oil chamber B, and
makes the piston rod 10C contract when supplied at the oil chamber
B with hydraulic oil from the main pump 11 and when discharging
hydraulic oil from the oil chamber A. When the hoist cylinder 10
extends, the vessel 3 is pivoted about the connecting pin 5
severing as a fulcrum toward the dumping position (refer to FIG.
2). When the hoist cylinder 10 contracts, the vessel 3 is pivoted
about the connecting pin 5 severing as the fulcrum toward the
transportation position (refer to FIG. 1).
[0033] The vehicle frame 2 is provided with a hoist shaft 133 being
a cylindrical member extending horizontally in the right-left
direction (refer to FIG. 1). As shown in FIG. 3, the hoist cylinder
10 is provided with a bore 102 (refer to FIG. 7A) at an extreme end
portion of the piston rod 10c (hereafter referred to as "rod head
101"), and a cylindrical bushing 134 is press-fitted in this bore
102. The bushing 134 is provided with a through bore 134h into
which the hoist shaft 133 is inserted. Likewise, a bore is provided
at an upper end part of the outer tube portion 10A of the hoist
cylinder 10, and a cylindrical bushing 154 is press-fitted in this
bore. The bushing 154 is provided with a through bore 154h into
which a vessel mounting pin (not shown) provided in a bracket (not
shown) of the vessel 3 is inserted.
[0034] The hoist shaft 133 is mounted with itself inserted into the
through bore 134h of the bushing 134 in the rod head 101 of the
piston rod 10C. The vessel mounting pin (not shown) is mounted with
itself inserted into the through bore 154h of the bushing 154 on
the outer tube portion 10A. Like this, the hoist cylinder 10 is
pivotably mounted to the vessel 3 at its one end part and is
pivotably mounted to the vehicle frame 2 at the other end part and
is able to extend and contract between the vessel 3 and the vehicle
frame 2.
[0035] The engine 9 has an output shaft coupled with a main pump 11
and a pilot pump 34. The main pump 11 and the pilot pump 34 are
rotationally driven by the engine 9, and are each a hydraulic pump
that discharges hydraulic oil stored in a hydraulic oil reservoir
12.
[0036] The main pump 11 and the hydraulic oil reservoir 12
configure a hydraulic power source that supplies hydraulic oil to
the hoist cylinder 10. The hydraulic oil reservoir 12 is located
under the vessel 3 and is attached to a lateral surface of the
vehicle frame 2 (refer to FIG. 1 and FIG. 2).
[0037] The hydraulic oil stored in the hydraulic oil reservoir 12
is discharged as pressurized oil from a discharge side of the main
pump 11 into a high-pressure pump pipe conduit 13 when the main
pump 11 is rotationally driven by the engine 9. Further, the return
oil from the hoist cylinder 10 is discharged to the hydraulic oil
reservoir 12 through a low-pressure reservoir pipe conduit 14.
[0038] The hoist cylinder 10 is connected with a hydraulic pipe
conduit 15A at the oil chamber A and with a hydraulic pipe conduit
15B at the oil chamber B. The hydraulic pipe conduits 15A, 15B are
connected to the main pump 11 and the hydraulic oil reservoir 12
constituting the hydraulic power source through the valve 16.
[0039] The valve 16 is provided between the hydraulic power source
(i.e., the main pump 11 and the hydraulic oil reservoir 12) and the
hoist cylinder 10. The valve 16, when switched in response to a
pilot pressure from a pilot pressure generation device 33 (refer to
FIG. 4) described later, controls the flow of the hydraulic oil
supplied from the main pump 11 to the hoist cylinder 10 and the
flow of the hydraulic oil discharged from the hoist cylinder 10 to
the hydraulic oil reservoir 12. The valve 16 is provided with a
high-pressure side oil passage 17, a low-pressure side oil passage
18, a bypass oil passage 19, a first directional control valve 20,
and a second directional control valve 21. The first directional
control valve 20 and the second directional control valve 21 are
connected in parallel to each other through the high-pressure side
oil passage 17 and the low-pressure side oil passage 18 and
further, are in a tandem connection through the bypass oil passage
19.
[0040] The high-pressure side oil passage 17 is connected to the
discharge side of the main pump 11 through the pump pipe conduit
13, while the low-pressure side oil passage 18 is connected to the
hydraulic oil reservoir 12 through the reservoir pipe conduit 14.
When the first directional control valve 20 and the second
directional control valve 21 are both at a neutral position (a),
the bypass oil passage 19 makes the high-pressure side oil passage
17 communicate with the low-pressure side oil passage 18 to bring
the main pump 11 into an unloaded state, so that the discharge
pressure (the pressure in the pump pipe conduit 13) is kept in a
low-pressure state being close to the reservoir pressure.
[0041] The first directional control valve 20 is provided on the
output side with a pair of actuator-side oil passages 22A, 22B. The
actuator-side oil passages 22A, 22B are connected to the oil
chambers A, B of the hoist cylinder 10 through the hydraulic pipe
conduits 15A, 15B, respectively. The second directional control
valve 21 is provided on the output side with a pair of
actuator-side oil passages 23A, 23B. The actuator-side oil passages
23A, 23B are connected to the oil chambers A, B of the hoist
cylinder 10 through the hydraulic pipe conduits 15A, 15B,
respectively.
[0042] The first directional control valve 20 and the second
directional control valve 21 are each a hydraulically piloted
6-port 3-position directional control valve. The first directional
control valve 20 is provided with a pair of hydraulic pilot
portions 20A, 20B. The first directional control valve 20 is
switched from the neutral position (a) to a rise position (b) when
supplied with a pilot pressure Pb at the hydraulic pilot portion
20A and is switched from the neutral position (a) to a floating
position (c) when supplied with a pilot pressure Pc at the
hydraulic pilot portion 20B. The second directional control valve
21 is provided with a pair of hydraulic pilot portions 21A, 21B.
The second directional control valve 21 is switched from the
neutral position (a) to a rise position (b) when supplied with the
pilot pressure Pb at the hydraulic pilot portion 21A and is
switched from the neutral position (a) to a fall position (d) when
supplied with a pilot pressure Pd at the hydraulic pilot portion
21B. Description will later be made regarding the configuration of
a pilot pressure generation device 33 that generates the pilot
pressures Pb, Pc and Pd for switching the first directional control
valve 20 and the second directional control valve 21.
[0043] As shown in FIG. 3, the valve 16 is provided with check
valves 24A, 24B for makeup purpose that are arranged on the first
directional control valve 20 side. The check valves 24A, 24B are
provided between the actuator-side oil passages 22A, 22B and the
low-pressure side oil passage 18 to detour the first directional
control valve 20. The check valves 24A, 24B are non-return valves
that allow the hydraulic oil in the hydraulic oil reservoir 12 to
flow from the low-pressure side oil passage 18 through the
actuator-side oil passages 22A, 22B and the hydraulic pipe conduits
15A, 15B to the oil chambers A, B of the hoist cylinder 10, but
prevent the flow in the opposite direction. Thus, the oil chambers
A, B of the hoist cylinder 10 are replenished with hydraulic oil
and are prevented from becoming a negative pressure.
[0044] The valve 16 is provided with relief valves 25A, 25B for
overload protection. The relief valves 25A, 25B are provided
between the actuator-side oil passages 22A, 22B and the
low-pressure side oil passage 18 to detour the first directional
control valve 20. The relief valves 25A, 25B are connected in
parallel relation with the check valves 24A, 24B. The relief valve
25A opens when an overload in the contract direction acts on the
hoist cylinder 10, to release the excess pressure on the oil
chamber A side. The relief valve 25B opens when an overload in the
extension direction acts on the hoist cylinder 10, to release the
excess pressure on the oil chamber B side.
[0045] The valve 16 is provided with check valves 26A, 26B for
makeup purpose that are arranged on the second directional control
valve 21 side. The check valves 26A, 26B are provided between the
actuator-side oil passages 23A, 23B and the low-pressure side oil
passage 18 to detour the second directional control valve 21. The
check valves 26A, 26B are non-return valves that allow the
hydraulic oil in the hydraulic oil reservoir 12 to flow from the
low-pressure side oil passage 18 through the actuator-side oil
passages 23A, 23B and the hydraulic pipe conduits 15A, 15B to the
oil chambers A, B of the hoist cylinder 10, but prevent the flow in
the opposite direction. Thus, the oil chambers A, B of the hoist
cylinder 10 are replenished with hydraulic oil and are prevented
from becoming a negative pressure.
[0046] The valve 16 is provided with a relief valve 27 arranged
between the high-pressure side oil passage 17 and the low-pressure
side oil passage 18. The relief valve 27 is a relief valve which is
variable in relief set pressure and prescribes the maximum
discharge pressure of the main pump 11. When a pressure exceeding
the maximum discharge pressure is generated, the relief valve 27
releases the excess pressure to the hydraulic oil reservoir 12.
[0047] The relief valve 27 has a variable pressure setting portion
27A supplied with the pilot pressure Pb. When the pilot pressure Pb
acts on the variable pressure setting portion 27A, the relief set
pressure is switched to a high-pressure setting. On the contrary,
when the supply of the pilot pressure Pb is stopped, the relief set
pressure of the relief valve 27 is switched to a low-pressure
setting.
[0048] FIG. 4 is a control block diagram of the dump truck 1. As
shown in FIG. 4, the dump truck 1 is provided with a controller
(control device) 32, an operating lever device 28, a pilot pressure
generation device 33, a grease feed device (lubricant supplier) 36,
a seating sensor (seating detection device) 30, an angle sensor 59,
and a stroke sensor 69.
[0049] The controller 32 is connected on the input side with
detection devices such as a lever sensor 29, the seating sensor 30,
the angle sensor 59, the stroke sensor 69 and the like and is
connected on the output side with the pilot pressure generation
device 33, the grease feed device 36 and the like. The controller
32 is configured to include an arithmetic processing device having
a CPU, a storage section 32A such as a ROM, a RAM and the like, and
other peripheral circuits and executes the control of the overall
system of the dump truck 1.
[0050] The operating lever device 28 is operator means for
operating the vessel 3 and is composed of, for example, an electric
lever device. The operating lever device 28 has an operating lever
28A and the lever sensor 29 that detects the operating position of
the operating lever 28A. The operating lever 28A is an operation
member that the operator in the cab 6 pivotally operates by
hand.
[0051] The operating lever 28A can take a hold position 28A1
indicated by the solid line in FIG. 4 and a floating position 28A2
indicated by the two-dot-chain line and usually takes the hold
position 28A1. The hold position 28A1 is an operation position that
makes the vessel 3 to be stopped and held at a desired position.
When the operator releases the operating lever 28A from his/her
hand in the state that the operating lever 28A is pivotally
operated from the hold position 28A1 in the arrow R direction, the
operating lever 28A is automatically returned by a first return
spring (not shown) to the hold position 28A1. When the operator
operates the operating lever 28A from the hold position 28A1 to the
floating position 28A2, the operating lever 28A is self-held at the
floating position 28A2 by a well-known detent mechanism (not
shown). When the operator releases the operating lever 28A from
his/her hand in the state that the operating lever 28A is pivotally
operated from the floating position 28A2 in the arrow L direction,
the operating lever 28A is automatically returned by a second
return spring (not shown) to the floating position 28A2.
[0052] The lever sensor 29 detects the operation position of the
operating lever 28A pivotally operated by the operator and outputs
its detection signal to the controller 32. The controller 32
determines the switching position of the valve 16 in dependence on
the operation position of the operating lever 28A and outputs a
control signal corresponding to the switching position to the pilot
pressure generation device 33.
[0053] The pilot pressure generation device 33 is, for example, an
electric-hydraulic conversion device constituted by an
electromagnetic proportional valve and converts control signals
(electric signals) from the controller 32 into the pilot pressures
(hydraulic signals) Pb, Pc and Pd. The pilot pressure generation
device 33 is provided with four operation sections comprising a
hold operation section 33A, a rise operation section 33B, a
floating operation section 33C, and a fall operation section
33D.
[0054] The pilot pump 34 is rotationally driven by the engine 9 to
supply the pilot pressure generation device 33 with pressurized oil
of the degree ranging, for example, from 0.5 to 5.0 MPa
(Mega-pascal). On the basis of the operation position of the
operating lever 28A, the pilot pressure generation device 33
outputs the pressurized oil from the pilot pump 34 as the pilot
pressures Pb, Pc and Pd to the valve 16 (refer to FIG. 3).
[0055] The controller 32 outputs a control signal to any one only
at a time of the hold operation section 33A, the rise operation
section 33B, the floating operation section 33C and the fall
operation section 33D, during which the controller 32 does not
output the control signal to any other operation section.
[0056] When the operating lever 28A is placed at the hold position
28A1, the controller 32 outputs the control signal to the hold
operation section 33A of the pilot pressure generation device 33.
The pilot pressure generation device 33 does not output any of the
pilot pressures Pb, Pc and Pd while the control signal is inputted
to the hold operation section 33A.
[0057] Thus, the valve 16 shown in FIG. 3 turns to "hold position"
with the first directional control valve 20 and the second
directional control valve 21 each taking the hold position assigned
to the neutral position (a). The switching of the valve 16 to the
hold position stops the supply of the hydraulic oil from the main
pump 11 to the hoist cylinder 10 and the discharge of hydraulic oil
from the hoist cylinder 10 to the hydraulic oil reservoir 12. That
is, with the valve 16 switched to "hold position", the hoist
cylinder 10 is stopped from movement to be held, whereby the vessel
3 is stopped and held at the present position.
[0058] As shown in FIG. 4, when the operating lever 28A is operated
from the hold position 28A1 to the rise side (in the arrow R
direction), the controller 32 outputs the control signal to the
rise operation section 33B of the pilot pressure generation device
33. The rise operation section 33B, when given the control signal
inputted from the controller 32, outputs the pilot pressure Pb to
the hydraulic pilot portion 20A of the first directional control
valve 20 and the hydraulic pilot portion 21A of the second
directional control valve 21 which are shown in FIG. 3. At this
time, a pressure close to the reservoir pressure acts as the pilot
pressure on the hydraulic pilot portion 20B of the first
directional control valve 20 and the hydraulic pilot portion 21B of
the second directional control valve 21.
[0059] Thus, the valve 16 turns to "rise position" with the first
directional control valve 20 and the second directional control
valve 21 each switched from the neutral position (a) to the rise
position (b). With the switching of the second directional control
valve 21 to the rise position (b), the pressurized oil discharged
from the main pump 11 is supplied to the oil chamber A of the hoist
cylinder 10 through the pump pipe conduit 13, the high-pressure
side oil passage 17, the second directional control valve 21, the
actuator-side oil passage 23A and the hydraulic pipe conduit 15A.
With the switching of the first directional control valve 20 to the
rise position (b), the hydraulic oil in the oil chamber B is
discharged to the hydraulic oil reservoir 12 through the hydraulic
pipe conduit 15B, the actuator-side oil passage 22B, the first
directional control valve 20, the low-pressure side oil passage 18
and the reservoir pipe conduit 14. While the valve 16 is switched
to "rise position", the piston rod 10C of the hoist cylinder 10
continues to extend and lifts up the front part side of the vessel
3, and thus, the vessel 3 is pivotally moved toward the dumping
position (refer to FIG. 2). That is, the vessel 3 rises up.
[0060] As shown in FIG. 4, when the operating lever 28A is operated
from the hold position 28A1 to the floating position 28A2, the
controller 32 outputs the control signal to the floating operation
section 33C of the pilot pressure generation device 33. With the
control signal inputted from the controller 32, the floating
operation section 33C outputs the pilot pressure Pc to the
hydraulic pilot portion 20B of the first directional control valve
20 shown in FIG. 3. At this time, a pressure close to the reservoir
pressure acts as the pilot pressure on the hydraulic pilot portion
20A of the first directional control valve 20 and the hydraulic
pilot portions 21A, 21B of the second directional control valve
21.
[0061] Thus, the valve 16 turns to "floating position" with the
first directional control valve 20 switched from the neutral
position (a) to the floating position (c) and with the second
directional control valve 21 switched to the neutral position (a).
When the first directional control valve 20 is switched to the
floating position (c), the actuator-side oil passage 22A is
connected to the the low-pressure side oil passage 18 and the
reservoir pipe conduit 14 through the first directional control
valve 20. Further, the actuator-side oil passage 22B is connected
to the the low-pressure side oil passage 18 and the reservoir pipe
conduit 14 through the check valve 24B, and at the same time, the
actuator-side oil passage 23B is connected to the low-pressure side
oil passage 18 and the reservoir pipe conduit 14 through the check
valve 26B. When the valve 16 is switched to "floating position",
the hoist cylinder 10 contracts by virtue of the load (dead weight)
of the vessel 3, and this causes the hydraulic oil in the oil
chamber A to be discharged to the hydraulic oil reservoir 12
through the hydraulic pipe conduit 15A, the actuator-side oil
passage 22A, the first directional control valve 20, the
low-pressure side oil passage 18 and the reservoir pipe conduit 14.
Further, the oil chamber B is replenished with the hydraulic oil in
the hydraulic oil reservoir 12 from the check valves 24B, 26B
through the actuator-side oil passages 22B, 23B and the hydraulic
pipe conduit 15B. In short, with the valve 16 switched to "floating
position", the vessel 3 is allowed to fall by virtue of its dead
weight. Therefore, the vessel 3 pivotally moves (is tilted)
downward to lower the front part side, so that the vessel 3 is
seated on the vehicle frame 2 (refer to FIG. 1).
[0062] As shown in FIG. 4, when the the operating lever 28A is
operated from the floating position 28A2 toward the fall side (in
the arrow L direction), the controller 32 outputs the control
signal to the fall operation section 33D of the pilot pressure
generation device 33. When given the control signal inputted from
the controller 32, the fall operation section 33D outputs the pilot
pressure Pd to the hydraulic pilot portion 21B of the second
directional control valve 21 shown in FIG. 3. At this time, a
pressure close to the reservoir pressure acts as the pilot pressure
on the hydraulic pilot portion 21A of the second directional
control valve 21 and the hydraulic pilot portions 20A, 20B of the
first directional control valve 20.
[0063] Thus, the valve 16 turns to "fall position" with the first
directional control valve 20 switched to the neutral position (a)
and with the second directional control valve 21 switched from the
neutral position (a) to the fall position (d). When the second
directional control valve 21 is switched to the fall position (d),
the hydraulic oil from the main pump 11 is supplied to the oil
chamber B of the hoist cylinder 10 through the pump pipe conduit
13, the high-pressure side oil passage 17, the second directional
control valve 21, the actuator-side oil passage 23B and the
hydraulic pipe conduit 15B. Further, the hydraulic oil in the oil
chamber A is discharged to the hydraulic oil reservoir 12 through
the hydraulic pipe conduit 15A, the actuator-side oil passage 23A,
the second directional control valve 21, the low-pressure side oil
passage 18 and the reservoir pipe conduit 14. While the valve 16 is
switched to "fall position", the hoist cylinder 10 causes the
cylindrical inner tube portion 10B to contract together with the
piston rod 10C into the cylindrical outer tube portion 10A due to
the pressurized oil supplied in the oil chamber B. In short, the
hoist cylinder 10 causes the vessel 3 to pivotally move (tilt)
downward to lower the front part side of the vessel 3 by the
hydraulic power, whereby the vessel 3 is seated on the vehicle
frame 2 (refer to FIG. 1).
[0064] As shown in FIG. 4, the angle sensor 59 is provided at the
connection portion of the vessel 3 with the vehicle frame 2 and
detects the pivotal angle of the vessel 3 that pivotally moves
about the connecting pin 5 serving as the pivotal fulcrum, to
output a detection signal to the controller 32. The pivotal angle
.theta. is set to become .theta.min when the vessel 3 is in the
seated state of being at the transportation position, become larger
in its value as the vessel 3 is pivotally moved toward the dumping
position, and become .theta.max when the vessel 3 is positioned to
the dumping position.
[0065] The stroke sensor 69 detects the stroke position S of the
hoist cylinder 10 and outputs a detection signal to the controller
32. The stroke position S is set so that, for example, the value
becomes Smin with the hoist cylinder 10 made to contract most,
becomes larger with the extension of the hoist cylinder 10 and
becomes Smax in the state that the hoist cylinder 10 extends to its
extreme end.
[0066] The seating sensor 30 detects whether the vessel 3 is seated
on the vehicle frame 2 or not, and outputs a detection signal to
the controller 32. As shown in FIG. 1 and FIG. 2, the seating
sensor 30 is disposed on an upper part of the hydraulic oil
reservoir 12. FIG. 5 is a side view showing the configuration of
the seating sensor 30. As shown in FIG. 5, the seating sensor 30 is
a touch-type sensor installed on the vehicle frame 2 side and is
provided with a rod-like touch terminal 30B. At the bottom part 3c
of the vessel 3, a protruding portion 30A is provided that is
arranged to brought into contact with the touch terminal 30B when
the vessel 3 is seated on the vehicle frame 2. When the protruding
portion 30A being a target to be detected is in contact with the
touch terminal 30B, the seating sensor 30 outputs an ON-signal to
the controller 32. When the protruding portion 30A is separated
from the touch terminal 30B not to effect the contact between the
both members, the the seating sensor 30 outputs an OFF-signal to
the controller 32. In the present specification, outputting the
OFF-signal means that the ON-signal (control current) is not
outputted to the controller 32, and this encompasses outputting a
control current differing from the ON-signal and not outputting the
control current.
[0067] FIG. 6 is a circuit diagram showing the configuration of the
grease feed device 36. As shown in FIG. 6, the grease feed device
36 is provided with a grease feed control valve 360, a grease feed
motor 361, a grease feed pump 362 and a grease feed reservoir 369
storing lubricant (lubrication oil) such as grease. The grease feed
control valve 360 is an electromagnetic changeover valve that is
switched between a closed position (g) and an open position (h) in
response to a control signal (exciting current to a solenoid)
outputted from the controller 32. When an ON-signal is outputted
from the controller 32, the grease feed control valve 360 excites
the solenoid to be switched to the open position (h). When an
OFF-signal is outputted from the controller 32, the grease feed
control valve 360 demagnetizes the solenoid to be switched by a
spring force to the closed position (g).
[0068] The grease feed motor 361 is a hydraulic motor for lubricant
supply that is driven by the pressurized oil discharged from the
main pump 11. The grease feed motor 361 is coupled at its
rotational shaft to a rotational shaft of the grease feed pump 362.
The grease feed pump 362 discharges lubricant stored in the grease
feed reservoir 369 when rotationally driven by the grease feed
motor 361. A discharge side of the grease feed pump 362 is
connected through a grease feed hose 35 to a grease feed hole 111
in the rod head 101 of the hoist cylinder 10.
[0069] When the grease feed control valve 360 is switched to the
open position (h), the grease feed motor 361 is driven by the
pressurized oil discharged from the main pump 11. The driving of
the grease feed motor 361 effects the driving of the grease feed
pump 362, whereby lubricant discharged from the grease feed pump
362 is supplied to the rod head 101 of the hoist cylinder 10
through the grease feed hose 35. When the grease feed control valve
360 is switched to the closed position (g), the rotation of the
grease feed pump 362 is stopped, whereby the supply of the
lubricant to the rod head 101 is discontinued.
[0070] The details of the connection portion between the hoist
cylinder 10 and the hoist shaft 133 will be described with
reference to FIG. 7A to FIG. 9. FIG. 7A is a schematic
longitudinal-sectional view of the connection portion between the
hoist cylinder 10 and the hoist shaft 133, taken along an imaginary
plane parallel to the center axis CL of the hoist shaft 133. FIG.
7B is a fragmentary enlarged view of a portion C in FIG. 7A. As
mentioned earlier, the rod head 101 of the hoist cylinder 10 is
provided with the bore 102 into which the cylindrical bushing 134
is press-fitted. The bushing 134 is provided with the cylindrical
through bore 134h that enables the hoist shaft 133 to pass through.
The hoist shaft 133 is inserted into the through bore 134h of the
bushing 134, which connects the hoist cylinder 10 with the vehicle
frame 2. Sliding is enabled between the internal surface of the
bushing 134 and the surface of the hoist shaft 133, so that the
hoist cylinder 10 is pivotable about the hoist shaft 133 serving as
the pivotal fulcrum.
[0071] FIG. 8 and FIG. 9 are each a fragmentary cross-sectional
view of the connection portion between the hoist cylinder 10 and
the hoist shaft 133, taken along an imaginary plane (A-A plane in
FIG. 7A) perpendicular to the center axis CL of the hoist shaft
133. For the convenience in description, a clearance between the
surface of the hoist shaft 133 and the internal surface of the
through bore 134h of the bushing 134 is illustrated in an
exaggerated scale. FIG. 8 shows the positional relation between the
bushing 134 and the hoist shaft 133 in the state that the vessel 3
is seated on the vehicle frame 2 and that the valve 16 is placed at
the floating position. FIG. 9 shows the positional relation between
the bushing 134 and the hoist shaft 133 in the state that the hoist
cylinder 10 is made to contract by a predetermined amount from the
state shown in FIG. 8.
[0072] As shown in FIG. 8 and FIG. 9, the hoist cylinder 10 is
provided with the grease feed hole 111 being a through hole for
grease feed. The grease feed hole 111 is connected to the grease
feed hose 35. As mentioned before, the grease feed hose 35 is
connected at one end to the grease feed hole 111 and at the other
end to the discharge side of the grease feed pump 362 of the grease
feed device 36 (refer to FIG. 6).
[0073] As shown in FIG. 7B, a groove (hereafter noted as an outer
circumferential groove 134a) that leads lubricant supplied from the
grease feed device 36 is provided on the surface of the bushing 134
in the circumferential direction. A plurality (four in the example
shown in FIG. 8 and FIG. 9) of communication holes 134t that make a
gap in the outer circumferential groove 134a communicate with a
clearance between the surface of the hoist shaft 133 and the
internal surface of the through bore 134h of the bushing 134 are
provided in the outer circumferential groove 134a at equiangular
intervals.
[0074] On the internal surface of the bushing 134 on the opposite
side of the outer circumferential groove 134a, there is provided in
the circumferential direction a groove (hereafter noted as an inner
circumferential groove 134b) that leads the lubricant introduced
from the outer circumferential groove 134a through the plurality of
the communication holes 134t to the whole circumference between the
surface of the hoist shaft 133 and the internal surface of the
through bore 134h of the bushing 134.
[0075] In the haulage vehicle, it is conventional that the valve 16
is switched to the floating position to let the vessel 3 to be
seated on the vehicle frame 2 by virtue of the dead weight.
Further, it is also conventional that also during the traveling of
the vehicle, the valve 16 is held to remain at the floating
position to keep the contraction state of the hoist cylinder 10 by
making use of the dead weight of the hoist cylinder 10. As shown in
FIG. 1, where the valve 16 has been switched to the floating
position with the vessel 3 seated on the vehicle frame 2, the dead
weight of the hoist cylinder 10 is supported by the hoist shaft
133, as shown in FIG. 8. Thus, a surface upper part a of the hoist
shaft 133 comes to close contact with the internal surface upper
part of the through bore 134h of the bushing 134. Incidentally,
similarly to this, when the hoist shaft 133 supports the load of
the vessel 3 as shown in FIG. 2, the surface upper part a of the
hoist shaft 133 is in close contact with the internal surface upper
part of the through bore 134h of the bushing 134. When the hoist
shaft 133 and the bushing 134 are in close contact at the upper
parts thereof, a clearance CS1 is formed between a surface lower
part .beta. of the hoist shaft 133 and an internal surface lower
part of the through bore 134h of the bushing 134.
[0076] Like this, in the haulage vehicle, the hoist shaft 133 and
the bushing 134 are in close contact at the upper parts thereof
during the dumping work and the traveling as shown in FIG. 8.
Accordingly, even when lubricant is supplied between the hoist
shaft 133 and the bushing 134, it is unable for the lubricant to
peLmeate satisfactorily into the close-contact portion at the upper
parts. As a result, the progress of abrasion of the bushing 134 at
the upper close-contact portion becomes faster than other portions
(for example, the internal surface lower part of the bushing 134).
Because it becomes necessary to replace the bushing 134 when the
same reaches the limit of abrasion even partly, it is undesirable
that abrasion being uneven or not uniform from those at other
potions proceeds at the close-contact portion. Therefore, in the
present embodiment, the hoist cylinder 10 is made to contract
slightly with the vessel 3 seated on the vehicle frame 2, and
lubricant is supplied in the state that as shown in FIG. 9, a
clearance CS2 is formed between the surface upper part a of the
hoist shaft 133 and the internal surface upper part of the through
bore 134h of the bushing 134. Hereafter, description will be made
regarding the details of a lubricant supply control (i.e., the
contract control of the hoist cylinder 10 and the driving control
of the grease feed device 36) by the controller 32.
[0077] As shown in FIG. 4, the controller 32 executes the lubricant
supply control in accordance with a lubricant supply control
program stored in the storage section 32A. The controller 32 is
provided as functions thereof with an operation judgment section
320, a seating judgment section 321, a valve control section
(lubricant supply control section) 322 and a grease feed control
section (lubricant supply control section) 323.
[0078] The operation judgment section 320 judges based on
information on the pivotal angle of the vessel 3 detected by the
angle sensor 59 whether or not, the vessel 3 is pivoting from the
dumping position side in the direction toward the transportation
position, that is, whether or not, the vessel 3 is being operated
to fall. When the pivotal angle .theta. decreases, the operation
judgment section 320 judges that the fall operation of the vessel 3
is being performed. Incidentally, that the fall operation of the
vessel 3 is being performed means the operation being in a
non-seated state that the vessel 3 is not seated on the vehicle
frame 2, and thus, the judgment whether the vessel 3 is being
operated to fall or not corresponds to making a judgment whether to
be in the non-seated state or not.
[0079] When the vessel 3 is judged to be in a fall operation, the
seating judgment section 321 judges based on the signal from the
seating sensor 30 whether the vessels 3 is seated or not. When
given the ON-signal inputted from the seating sensor 30, the
seating judgment section 321 judges that the vessel 3 is seated,
that is, the vessel 3 is at the transportation position. When given
the OFF-signal outputted from the seating sensor 30, the seating
judgment section 321 judges that the vessel 3 is not seated, that
is, the vessel 3 is not at the transportation position.
[0080] When the vessel 3 is judged to be seated, the valve control
section 322 outputs a control signal to the fall operation section
33D of the pilot pressure generation device 33 to switch the second
directional control valve 21 of the valve 16 to the fall position
(d), and this causes the hoist cylinder 10 to contract until the
stroke position S of the hoist cylinder 10 becomes a threshold
value S0. When the stroke position S detected by the stroke sensor
69 becomes equal to or less than the threshold value S0, the valve
control section 322 outputs a control signal to the hold operation
section 33A of the pilot pressure generation device 33 to switch
the first directional control valve 20 and the second directional
control valve 21 of the valve 16 to the neutral position (a),
whereby the hoist cylinder 10 discontinues the operation to keep
the contraction state. Incidentally, the threshold value S0
designates the stroke position S that the hoist cylinder 10 has
when the vessel 3 is seated on the vehicle frame 2 and when as
shown in FIG. 9, the surface lower part .beta. of the hoist shaft
133 contacts the internal surface lower part of the bushing 134 of
the rod head 101, and is stored beforehand in the storage section
32A of the controller 32 (Smin.ltoreq.S0<Smax).
[0081] When the vessel 3 is judged to be seated, the grease feed
control section 323 outputs the ON-signal to the grease feed
control valve 360 of the grease feed device 36 to switch the grease
feed control valve 360 to the open position (h) and drives the
grease feed device 36 until the driving period of time (i.e.,
greasing period of time) of the grease feed device 36 becomes a
time threshold value tO or longer. The time threshold value t0 is
stored beforehand in the storage section 32A of the controller 32.
The grease feed control section 323 judges whether the state that
the grease feed pump 362 is supplying lubricant to the hoist
cylinder 10 has been continued for the period of the time threshold
value t0 or longer. If the grease feed time t counted by a timer
built in the controller 32 becomes the time threshold value t0 or
longer, the grease feed control section 323 judges that a grease
feed end condition is satisfied, and outputs the OFF-signal to the
grease feed control valve 360, whereby the grease feed control
valve 360 is switched to the closed position (g) to stop the grease
feed device 36.
[0082] After the supply of lubricant by the grease feed device 36
is discontinued upon satisfaction of the grease feed end condition,
the valve control section 322 outputs the control signal to the
floating operation section 33C of the pilot pressure generation
device 33 to switch the first directional control valve 20 of the
valve 16 to the floating position (c).
[0083] FIG. 10 is a flowchart showing the processing details of the
lubricant supply control by the controller 32 according to the
present embodiment. The processing shown in this flowchart is
started for example by turning a starter switch (i.e., ignition
switch, not shown) to ON and is repetitively executed in a
predetermined control cycle after the execution of an initial
setting (not shown). Although not shown, the controller 32 is
designed to acquire information from various sensors such as the
seating sensor 30, the angle sensor 59, the lever sensor 29, the
stroke sensor 69 and the like on a predetermined control cycle.
[0084] At step S110, the controller 32 judges based on the signal
from the angle sensor 59 whether the vessel 3 is being operated to
fall or not. The step S110 is repeated until an affirmative
judgment is made, and the processing proceeds to step S120 when the
affirmative judgment is made. At step 120, the controller 32 sets
to 0 (zero) a grease feed period of time t that is counted by a
timer built in the controller 32, that is, initializes the grease
feed period of time t (i.e., resets the timer) and then, advances
the processing to step 130.
[0085] At step S130, the controller 32 judges based on the signal
from the seating sensor 30 whether the vessel 3 is seated on the
vehicle frame 2 or not. The step S130 is repeated until an
affirmative judgment is made, and the processing proceeds to step
S140 when the affirmative judgment is made. When the affirmative
judgment is made at step 130, the controller 32 judges that the
vessel 3 has turned from the non-seated state in which the vessel 3
is not seated on the vehicle frame 2 to the seated state in which
it is seated, and then executes the lubricant supply control (steps
S140 through S170).
[0086] At step S140, the controller 32 outputs a control signal to
the fall operation section 33D (refer to FIG. 4) of the pilot
pressure generation device 33 and proceeds to step S143. Thus, the
pilot pressure Pd is outputted from the pilot pressure generation
device 33 to the hydraulic pilot portion 21B of the second
directional control valve 21 of the valve 16, and thus, the second
directional control valve 21 is switched to the fall position (d)
(refer to FIG. 3). At this time, a pressure close to the reservoir
pressure acts on the hydraulic pilot portions 20A, 20B of the first
directional control valve 20, and thus, the first directional
control valve 20 is held switched to the neutral position (a).
[0087] At step S143, the controller 32 judges whether the stroke
position S is equal to or less than the threshold value S0 or not.
An affirmative judgment at step S143 results in going to step S147,
while a negative judgment at step S143 results in returning to step
S140.
[0088] At step S147, the controller 32 outputs a control signal to
the hold operation section 33A (refer to FIG. 4) of the pilot
pressure generation device 33 and proceeds to step S150. Thus, the
pressure acting on the hydraulic pilot portions 21A, 21B of the
second directional control valve 21 goes down to a pressure close
to the reservoir pressure, so that the second directional control
valve 21 is switched to the neutral position (a) (refer to FIG.
3).
[0089] At step S150, the controller 32 outputs the ON-signal to the
grease feed control valve 360 to switch the same to the open
position (h) (refer to FIG. 6) and then proceeds to step S153. At
step S153, the controller 32 executes a time counter increment
processing (t=t+.DELTA.t) in which the time .DELTA.t representing
the control cycle is added to the grease feed period of time t of
the built-in timer, and then proceeds to step S157.
[0090] At step S157, the controller 32 judges whether the grease
feed period of time t has become equal to or longer than the time
threshold value t0 or not. An affirmative judgment at step S157
results in going to step S160, while a negative judgment at step
S157 results in returning to step S150.
[0091] At step S160, the controller 32 outputs the OFF-signal to
the grease feed control valve 360 (i.e., discontinues the
outputting of the ON-signal (i.e., exciting current)) to switch the
grease feed control valve 360 to the closed position (g) (refer to
FIG. 6) and then proceeds to step S170.
[0092] At step S170, the controller 32 outputs a control signal to
the floating operation section 33C (refer to FIG. 4) of the pilot
pressure generation device 33 and terminates the processing shown
as the flowchart in FIG. 10. Thus, the pilot pressure Pc is
outputted from the pilot pressure generation device 33 to the
hydraulic pilot portion 20B of the first directional control valve
20 of the valve 16, whereby the first directional control valve 20
is switched to the floating position (c) (refer to FIG. 3).
[0093] The operation in the present embodiment will be summarized
as follows:
[0094] As shown in FIG. 1, the operator operates the dump truck 1
to transport the crushed rocks 4 loaded on the vessel 3 to a
designated place. As shown in FIG. 2, the operator operates the
operating lever 28A to the operation position on the rise side,
whereby the vessel 3 is tilted to dump the crushed rocks 4. Upon
completion of the dumping, the operator operates the operating
lever 28A to the floating position 28A2 (refer to FIG. 4) to let
the vessel 3 operate to fall by virtue of the dead weight.
[0095] The vessel 3 falls by virtue of its dead (empty) weight
about the connecting pin 5 acting as the pivotal fulcrum, and when
the vessel 3 is moved from the non-seated state in which the
protruding portion 30A provided as a target for detection on the
vessel 3 side is spaced from the seating sensor 30, to the seated
state in which the protruding portion 30A is in contact with the
touch terminal 30B (refer to FIG. 5) of the seating sensor 30, the
lubricant supply control is executed by the controller 32. In the
lubricant supply control, a switching control is executed to switch
the switching position of the pilot pressure generation device 33
to the fall position (from Yes at step S110 through Yes at step
S130 to step S140).
[0096] Therefore, the hoist cylinder 10 contracts further than it
does in the usual seated state with the valve 16 having been
switched to the floating position. When the hoist cylinder 10
contracts to have the stroke position S equal to or less than the
threshold value S0, the contract operation of the hoist cylinder 10
is discontinued, and the same is held at the discontinued position
(from Yes at step S143 to step S147). At this time, as shown in
FIG. 9, the surface lower part .beta. of the hoist shaft 133 and
the internal surface lower part of the through bore 134h of the
bushing 134 contact each other at a predetermined contact pressure,
so that the clearance CS2 is formed between the internal surface
upper part of the through bore 134h of the bushing 134 and the
surface upper part a of the hoist shaft 133.
[0097] In this state, lubricant is supplied from the grease feed
device 36 through the grease feed hose 35 to the grease supply hole
111 of the rod head 101 (from step S150 through step S153 to No at
step S157). The lubricant supplied to the rod head 101 is filled up
in the outer circumferential groove 134a of the bushing 134 shown
in FIG. 7B and is supplied to the clearance CS2 through the
communication holes 134t extending radially inward from the outer
circumferential groove 134a. The lubricant supplied to the
clearance CS2 peLmeates into the whole circumference of the hoist
shaft 133 through the inner circumferential groove 134b. As a
result, lubrication is given over the surface of the hoist shaft
133 and the internal surface of the through bore 134h of the
bushing 134.
[0098] The grease feed device 36 is automatically stopped after
being operated for a predetermined period of time (from Yes at step
S157 to step S160). Further, a switching control is performed to
switch the switching position of the valve 16 to the floating
position, whereby a reaction force accumulated at the contact
portion between the vessel 3 and the vehicle frame 2 causes the
hoist cylinder 10 to extend to a usual stroke position S=S1
(Smin.ltoreq.S0<S1<Smax) (step S170). Thus, as shown in FIG.
8, the surface upper part .alpha. of the hoist shaft 133 contacts
the internal surface upper part of the through bore 134h of the
bushing 134 at a predetermined contact pressure, whereby the
clearance CS1 is formed between the internal surface lower part of
the through bore 134h of the bushing 134 and the surface lower part
.beta. of the hoist shaft 133.
[0099] As described above, the present embodiment is applied to the
dump truck 1 having the vessel 3 provided pivotably relative to the
vehicle frame 2, the hoist cylinder 10 telescopically provided
between the vessel 3 and the vehicle frame 2, the main pump 11 for
supplying hydraulic oil to the hoist cylinder 10, and the valve 16
provided between the main pump 11 and the hoist cylinder 10 for
controlling the flow of hydraulic oil supplied to the hoist
cylinder 10.
[0100] According to the present embodiment like this, advantageous
effects can be accomplished as follows:
[0101] (1) The hoist shaft 133 provided in the vehicle frame 2 is
mounted with itself passing through the through bore 134h of the
bushing 134 provided at one end portion of the hoist cylinder 10.
When the seating sensor 30 detects the vessel 3 seated on the
vehicle frame 2, the controller 32 controls the valve 16 to make
the hoist cylinder 10 contract and also controls the grease feed
device 36 to supply lubricant to the clearance between the surface
of the hoist shaft 133 and the internal surface of the through bore
134h of the bushing 134.
[0102] Thus, since the hoist cylinder 10 contracts further than it
does in the usual seated state with the valve 16 switched to the
floating position, the clearance CS2 is formed between the surface
upper part .alpha. of the hoist shaft 133 and the internal surface
upper part of the through bore 134h of the bushing 134 which have
been held in close contact until then. In the present embodiment,
the hoist cylinder 10 is made to contract until the close contact
is made between the surface lower part .beta. of the hoist shaft
133 and the internal surface lower part of the through bore 134h of
the bushing 134, so that the clearance CS2 at the upper part is
made to be large. Thus, as shown in FIG. 9, the volume of the
clearance on the upper side of the imaginary horizontal plane H
encompassing the center axis CL of the hoist shaft 133 is made to
be larger than that on the lower side of the imaginary horizontal
plane H.
[0103] Lubricant is supplied in the state that the clearance CS2 at
the upper part is formed, and thus, the surface upper part a of the
hoist shaft 133 and the internal surface upper part of the through
bore 134h of the bushing 134 can be lubricated satisfactorily, so
that the upper parts of the bushing 134 and the hoist shaft 133 can
be restrained from abrading. As a result, an uneven abrasion of the
bushing 134 and the hoist shaft 133 can be restrained, and hence,
it is possible to improve the service lives of the bushing 134 and
the hoist shaft 133.
[0104] (2) When judging that movement progresses from the
non-seated state that the vessel 3 is not seated on the vehicle
frame 2 to the seated state that it is seated thereon, the
controller 32 controls the valve 16 to make the hoist cylinder 10
contract and also controls the grease feed device 36 to supply the
clearance CS2 with lubricant. Because the lubricant supply control
for the hoist cylinder 10 is executed to come upon the completion
of the dumping work, an unpleasant feeling that might be given to
the operator can be decreased in comparison with the case that the
lubricant supply control is executed during the traveling.
[0105] (3) After controlling the grease feed device 36 to supply
lubricant to the clearance CS2, the controller 32 switches the
valve 16 to the floating position (the usual seated position). In
the grease feeding, the hoist cylinder 10 is made to contract, and
this makes it possible to reduce the period of time in the state
that the surface lower part .beta. of the hoist shaft 133 is held
in contact with the internal surface lower part of the bushing 134,
that is, in the state that a load is applied to the hoist cylinder
10. Thus, the hoist cylinder 10 is improved in service life.
Further, when the valve 16 is switched to the floating position,
the clearance CS1 is formed as shown in FIG. 8 between the surface
lower part .beta. of the hoist shaft 133 and the internal surface
lower part of the through bore 134h of the bushing 134. Thus, the
lubricant flows by virtue of its gravity and can satisfactorily
lubricates the surface lower part .beta. of the hoist shaft 133 and
the internal surface lower part of the through bore 134h of the
bushing 134, so that the lower parts of the bushing 134 and the
hoist shaft 133 can be restrained from abrading.
[0106] (4) The outer circumferential groove 134a that leads the
lubricant supplied from the grease feed device 36 is provided in
the circumferential direction over the whole circumference of the
surface of the bushing 134 being a cylindrical member. The outer
circumferential groove 134a has the plurality of communication
holes 134t opening therein, and the lubricant supplied to the outer
circumferential groove 134a is led through the communication holes
134t to the clearance CS2 between the internal surface of the
bushing 134 and the surface of the hoist shaft 133. Thus, during
the lubricant supply control, it is possible to supply lubricant
smoothly between the hoist shaft 133 and the bushing 134.
[0107] The following modified forms are also within the scope of
the present invention, and it is also possible to combine one or
some of the modified forms with the foregoing embodiment.
(Modified Form 1)
[0108] Although in the foregoing embodiment, description has been
made about the example that uses the touch type sensor as the
seating sensor 30, the present invention is not limited to this.
The angle sensor 59 that detects the pivotal angle .theta. of the
vessel 3 using the connecting pin 5 as the pivotal fulcrum may be
used as the seating sensor 30. In this case, the controller 32
judges that the vessel 3 is seated on the vehicle frame 2 when the
pivotal angle .theta. of the vessel 3 detected by the angle sensor
59 becomes equal to or less than the angle threshold value
.theta.0. The angle threshold value .theta.0 is determined as a
pivotal angle which is made by adding a tolerance (e.g., one degree
or so) to the angle .theta.min that the vessel 3 has when seated,
and is stored beforehand in the storage section 32A of the
controller 32.
(Modified Form 2)
[0109] In the foregoing embodiment, description has been made
regarding the example wherein when movement progresses from the
non-seated state of the vessel 3 being not seated on the vehicle
frame 2 to the seated state of the vessel 3 being seated thereon,
the valve 16 makes the hoist cylinder 10 contract and the grease
feed device 36 supplies lubricant to the clearance CS2 between the
hoist shaft 133 and the bushing 134. However, the present invention
is not limited to this example.
(Modified Form 2-1)
[0110] For example, each time a predetermined period of time
elapses in the seated state of the vessel 3 being seated on the
vehicle frame 2, the controller 32 may control the valve 16 to make
the hoist cylinder 10 contract and may control the grease feed
device 36 to supply lubricant to the clearance CS2 between the
hoist shaft 133 and the bushing 134. By supplying lubricant at
regular intervals, it is possible to lubricate the surface of the
hoist shaft 133 and the internal surface of the through bore 134h
of the bushing 134.
(Modified Form 2-2)
[0111] A grease feed switch (not shown) may be provided in the cab
6, in which case the lubricant supply control may be executed when
the grease feed switch is operated in the state that the vessel 3
is judged to be in the seated state with itself being seated on the
vehicle frame 2.
(Modified Form 3)
[0112] In the foregoing embodiment, description has been made
regarding the example wherein the threshold value S0 of the stroke
position S is used as the stroke position S that the rod head 101
takes at a position where the surface lower part .beta. of the
hoist shaft 133 and the internal surface lower part of the bushing
134 in the rod head 101 contact each other. However, the present
invention is not limited to this example. The threshold value S0
may be such a stroke position S that can provide a clearance at
least between the surface upper part .alpha. of the hoist shaft 133
and the internal surface upper part of the bushing 134. For
example, a stroke position S at which the center axis CL of the
hoist shaft 133 becomes concentric with the center axis of the bore
102 of the rod head 101 may be stored as the threshold value S0 in
the storage section 32A. Incidentally, it is preferable that the
storage section 32A beforehand stores as the threshold value S0
such a stroke position S that makes the height dimension of the
upper clearance CS2 between the hoist shaft 133 and the bushing 134
longer than the height dimension of the lower clearance CS1.
(Modified Form 4)
[0113] In the foregoing embodiment, description has been made
regarding the example wherein the operation judgment section 320
judges based on the detection signal from the angle sensor 59
whether the vessel 3 is being operated to fall or not. However, the
present invention is not limited to this example. The operation
judgment section 320 may judge based on the detection signal from
the lever sensor 29 whether the operating lever 28A has been
operated from the state of being operated to the operation position
on the rise side or the hold position to the operation position on
the fall side or to the floating position, and when an affirmative
judgment is made, may judge that the vessel 3 is being operated to
fall, that is, the vessel 3 is in the non-seated state.
(Modified Form 5)
[0114] In the foregoing embodiment, description has been made
regarding the example wherein the judgment of whether the vessel 3
is in the non-seated state or not is made in dependence on whether
the vessel 3 is being operated to fall or not. However, the present
invention is not limited to this example. The controller 32 may
judge based on the detection signal from the seating sensor 30
whether the vessel 3 is in the non-seated state or not. In the
present modified form, when the vessel 3 is judged to be in the
seated state following the judgment of the vessel 3 being in the
non-seated state, the controller 32 may judge that the vessel 3 has
proceeded from the non-seated state to the seated state.
(Modified Form 6)
[0115] Before step S110 in FIG. 10, there may be added a floating
position operation judgment step of judging whether the operating
lever 28A is being operated to the floating position 28A2 or not.
This floating position operation judgment step is repeated until an
affirmative judgment is made, and when the operating lever 28A is
judged to have been operated to the floating position 28A2 (in the
case of the affirmative judgment), the processing proceeds to step
S110.
(Modified Form 7)
[0116] Although the dump truck 1 that supports the vessel 3 on the
vehicle frame 2 of the wheel type having the front wheels 7 and the
rear wheels 8 has been described by way of example in the foregoing
embodiment, the present invention is not limited to the dump truck
1. For example, the present invention is also applicable to a
haulage vehicle such as a crawler carrier which mounts a vessel on
a vehicle provided with a crawler-type traveling mechanism.
[0117] Although various embodiments and modified foLins have been
described as above, the present invention is not limited to these
embodiment and modified forms. It it to be noted that other forms
conceivable within the technical concept of the present invention
may be encompassed in the scope of the present invention.
* * * * *