U.S. patent application number 13/989882 was filed with the patent office on 2013-12-05 for electric construction machine.
This patent application is currently assigned to HITACHI CONSTRUCTION MACHINERY CO., LTD.. The applicant listed for this patent is Hajime Kurikuma, Akira Noguchi, Tatsuo Takishita, Masayuki Yunoue. Invention is credited to Hajime Kurikuma, Akira Noguchi, Tatsuo Takishita, Masayuki Yunoue.
Application Number | 20130318956 13/989882 |
Document ID | / |
Family ID | 46720583 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130318956 |
Kind Code |
A1 |
Yunoue; Masayuki ; et
al. |
December 5, 2013 |
ELECTRIC CONSTRUCTION MACHINE
Abstract
Provided is an electric construction machine capable of avoiding
a situation where charging is difficult to achieve due to the
exhaustion of a battery device. An electrically-operated hydraulic
excavator includes an electric motor, a hydraulic pump that is
driven by the electric motor, hydraulic actuators that are driven
by hydraulic fluid discharged from the hydraulic pump, and a
battery device that serves as an electrical power source for the
electric motor. The battery device includes battery systems that
each have a plurality of batteries. A selector switch makes it
possible to select either one of the battery systems. An arithmetic
control section of an inverter device controls connection change
switches through battery controllers to change the connections of
the battery systems so that electrical power is supplied to the
electric motor from either the battery system or the battery
system, whichever is selected by the selector switch.
Inventors: |
Yunoue; Masayuki; (Koka-shi,
JP) ; Noguchi; Akira; (Koka-shi, JP) ;
Takishita; Tatsuo; (Koka-shi, JP) ; Kurikuma;
Hajime; (Koka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yunoue; Masayuki
Noguchi; Akira
Takishita; Tatsuo
Kurikuma; Hajime |
Koka-shi
Koka-shi
Koka-shi
Koka-shi |
|
JP
JP
JP
JP |
|
|
Assignee: |
HITACHI CONSTRUCTION MACHINERY CO.,
LTD.
Tokyo
JP
|
Family ID: |
46720583 |
Appl. No.: |
13/989882 |
Filed: |
January 18, 2012 |
PCT Filed: |
January 18, 2012 |
PCT NO: |
PCT/JP2012/050999 |
371 Date: |
May 28, 2013 |
Current U.S.
Class: |
60/420 ; 60/427;
60/431 |
Current CPC
Class: |
E02F 9/2091 20130101;
E02F 3/325 20130101; E02F 9/2282 20130101; Y02T 10/6278 20130101;
Y02T 10/62 20130101; E02F 9/2285 20130101; E02F 9/207 20130101;
B60K 6/28 20130101 |
Class at
Publication: |
60/420 ; 60/427;
60/431 |
International
Class: |
E02F 9/20 20060101
E02F009/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2011 |
JP |
2011-035081 |
Claims
1. An electric construction machine comprising: an electric motor;
a hydraulic pump that is driven by the electric motor; a plurality
of hydraulic actuators that are driven by hydraulic fluid
discharged from the hydraulic pump; and a battery device that
serves as an electrical power source for the electric motor;
wherein the battery device includes a plurality of battery systems
that each have a plurality of series-connected batteries and are
mutually parallel-connected, wherein the electric construction
machine includes connection change control means that can change
the connections of the battery systems to select one of the battery
systems and let the selected battery system supply electrical power
to the electric motor, and display means for indicating a battery
system that supplies electrical power to the electric motor.
2. The electric construction machine according to claim 1, further
comprising: manual selection means that is manually operated to
select one of the battery systems; wherein the connection change
control means changes the connections of the battery systems so
that the battery system selected by the manual selection means
supplies electrical power to the electric motor.
3. The electric construction machine according to claim 1, further
comprising: a plurality of remaining battery power amount
acquisition means that acquires information about the amount of
electrical power remaining in each of the battery systems; motor
stop control means that stops the electric motor when a battery
system supplying electrical power to the electric motor is
exhausted; and automatic selection means that automatically selects
a battery system other than the exhausted battery system when a
preselected period of time elapses after the electric motor is
stopped by the motor stop control means; wherein the connection
change control means changes the connections of the battery systems
so that the battery system selected by the automatic selection
means supplies electrical power to the electric motor.
4. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrically-operated
hydraulic excavator and other electric construction machines, and
more particularly to electric construction machines having a
battery device that serves as an electrical power source for an
electric motor.
BACKGROUND ART
[0002] The electrically-operated hydraulic excavator, which is one
of the electric construction machines, includes, for example, a
hydraulic pump driven by an electric motor, a plurality of
hydraulic actuators (or more specifically, a boom hydraulic
cylinder, an arm hydraulic cylinder, a bucket hydraulic cylinder,
etc.), a plurality of operating means for specifying the operations
of the hydraulic actuators, and a plurality of directional control
valves for controlling the flow of hydraulic fluid from the
hydraulic pump to the hydraulic actuators in accordance with the
operations of the operating means.
[0003] A known electrically-operated hydraulic excavator has a
battery that serves as an electrical power source for an electric
motor. The battery is made, for instance, of lead, lithium ions, or
nickel hydride and divisible into a minimal unit called a cell. A
final commercially-available product of the battery is a module
that includes one pack of a plurality of cells. An
electrically-operated hydraulic excavator described, for instance,
in Patent Document 1 has a battery device that includes a plurality
of modules (namely, a plurality of batteries).
PRIOR ART LITERATURE
Patent Document
[0004] Patent Document 1: JP-2008-44408-A
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0005] However, the above prior art has the following problem. The
above-mentioned battery device is formed by series-connecting all
the batteries although it is not explicitly described in Patent
Document 1. Hence, the electric motor is driven by the electrical
power supplied from all the batteries. It means that all the
batteries are simultaneously used. Therefore, if the battery device
is to be charged because only a small amount of electrical power is
stored in the battery device while the electrically-operated
hydraulic excavator is operated, for instance, at a construction
site, the electrically-operated hydraulic excavator needs to travel
to a charging site by using its battery power or travel to the
load-carrying platform of a vehicle by using its battery power for
the purpose of being carried to the charging site. If all the
batteries are exhausted without the knowledge of an operator of the
electrically-operated hydraulic excavator, it is difficult to
achieve charging because the electrically-operated hydraulic
excavator is stopped and unable to travel by using its battery
power.
[0006] An object of the present invention is to provide an electric
construction machine that is capable of avoiding a situation where
charging is difficult to achieve due to the exhaustion of all of
its batteries.
Means for Solving the Problem
[0007] (1) In accomplishing the above object, according to an
aspect of the present invention, there is provided an electric
construction machine including an electric motor, a hydraulic pump,
a plurality of hydraulic actuators, and a battery device. The
hydraulic pump is driven by the electric motor. The hydraulic
actuators are driven by hydraulic fluid discharged from the
hydraulic pump. The battery device serves as an electrical power
source for the electric motor. The battery device includes a
plurality of battery systems which each have a plurality of
series-connected batteries. The battery systems are mutually
parallel-connected. The electric construction machine also includes
connection change control means that can change the connections of
the battery systems to select one of the battery systems and let
the selected battery system supply electrical power to the electric
motor.
[0008] According to the present invention, which is described
above, the battery device includes the battery systems and drives
the electric motor by allowing one of the battery systems to supply
electrical power. In other words, only one battery system is used
at a time. Therefore, even if the electric construction machine
stops because the battery system supplying electrical power to the
electric motor is exhausted without the knowledge of an operator of
the electric construction machine, the connection change control
means can switch to another battery system to let it supply
electrical power to the electric motor and operate the electric
construction machine. As the electric construction machine can
travel by using its battery power, it is possible to avoid a
situation where charging is difficult to achieve.
[0009] (2) According to another aspect of the present invention,
there is provided the electric construction machine as described in
(1) above, further including manual selection means that is
manually operated to select one of the battery systems. The
connection change control means changes the connections of the
battery systems so that the battery system selected by the manual
selection means supplies electrical power to the electric
motor.
[0010] Consequently, if a battery system supplying electrical power
to the electric motor is exhausted, the electric construction
machine is stopped until the operator manually operates the manual
selection means. This ensures that the operator certainly becomes
aware of the exhausted battery system.
[0011] (3) According to another aspect of the present invention,
there is provided the electric construction machine as described in
(1) above, further including a plurality of remaining battery power
amount acquisition means, motor stop control means, and automatic
selection means. The remaining battery power amount acquisition
means acquires information about the amount of electrical power
remaining in each of the battery systems. The motor stop control
means stops the electric motor when a battery system supplying
electrical power to the electric motor is exhausted. The automatic
selection means automatically selects a battery system other than
the exhausted battery system when a preselected period of time
elapses after the electric motor is stopped by the motor stop
control means. The connection change control means changes the
connections of the battery systems so that the battery system
selected by the automatic selection means supplies electrical power
to the electric motor.
[0012] Consequently, when a battery system supplying electrical
power to the electric motor is exhausted, the electric construction
machine remains stopped for the predetermined period of time. This
ensures that the operator certainly becomes aware of the exhausted
battery system.
[0013] (4) According to still another aspect of the present
invention, there is provided the electric construction machine as
described in (1), (2), or (3) above, further including display
means for indicating a battery system that supplies electrical
power to the electric motor.
Advantages of the Invention
[0014] The present invention makes it possible to avoid a situation
where charging is difficult to achieve due to the exhaustion of all
batteries.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a side view illustrating the overall structure of
an electrically-operated hydraulic excavator according to an
embodiment of the present invention.
[0016] FIG. 2 is a top view illustrating the overall structure of
the electrically-operated hydraulic excavator according to the
embodiment of the present invention.
[0017] FIG. 3 is a hydraulic circuit diagram illustrating the
configuration of a hydraulic drive device according to the
embodiment of the present invention.
[0018] FIG. 4 is a block diagram illustrating the configuration of
an inverter device and related equipment according to the
embodiment of the present invention.
[0019] FIG. 5 is a block diagram illustrating the configuration of
a battery device and related equipment according to the embodiment
of the present invention.
[0020] FIG. 6 is a flowchart illustrating a battery charge control
process according to the embodiment of the present invention.
[0021] FIG. 7 is a flowchart illustrating a motor drive control
process according to the embodiment of the present invention.
[0022] FIG. 8 is a flowchart illustrating a motor drive control
process according to a modified embodiment of the present
invention.
[0023] FIG. 9 is a block diagram illustrating the configuration of
an inverter device and related equipment according to the modified
embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0024] An embodiment of the present invention will now be described
with reference to the accompanying drawings on the assumption that
the present invention is applied, for instance, to an
electrically-operated hydraulic excavator.
[0025] FIG. 1 is a side view illustrating the overall structure of
the electrically-operated hydraulic excavator according to the
present embodiment. FIG. 2 is a top view. The front side (the right
side of FIG. 1), rear side (the left side of FIG. 1), left side
(the rear side of FIG. 1), and right side (the front side of FIG.
1) of an operator seated on a cab seat of the electrically-operated
hydraulic excavator shown in FIG. 1 are hereinafter simply referred
to as the front side, the rear side, the left side, and the right
side, respectively.
[0026] Referring to FIGS. 1 and 2, the electrically-operated
hydraulic excavator (a mini-excavator having an operating mass of
less than 6 tons in the present embodiment) includes a crawler-type
lower travel structure 1, an upper turning structure 2, a turning
frame 3, a swing post 4, a multi-joint work machine 5, a
canopy-type cab 6, and a battery device compartment 8. The upper
turning structure 2 is turnably mounted on the lower travel
structure 1. The turning frame 3 forms a basic lower structure for
the upper turning structure 2. The swing post 4 is mounted on the
front side of the turning frame 3 and can be turned in a left-right
direction. The multi-joint work machine 5 is coupled to the swing
post 4 and can be turned (elevated) in an up-down direction. The
canopy-type cab 6 is mounted on the turning frame 3. The battery
device compartment 8 is disposed on the rear side of the turning
frame 3 to house a battery device 7 (see later-referenced FIGS. 3
to 5).
[0027] The lower travel structure 1 includes a track frame 9, a
pair of left and right driving wheels 10, 10, a pair of left and
right driven wheels (idlers) 11, 11, and a pair of left and right
crawler belts 12, 12. The track frame 9 is substantially shaped
like the letter H when viewed from above. The driving wheels 10, 10
are positioned near the left and right rear ends of the track frame
9 and rotatably supported. The driven wheels 11, 11 are positioned
near the left and right front ends of the track frame 9 and
rotatably supported. The left and right crawler belts 12, 12 are
threaded around the left and right driving wheels 10 and driven
wheels 11. The left driving wheel 10 (namely, the left crawler belt
12) is rotationally driven by a left travel hydraulic motor 13A
(see later-referenced FIG. 3). The right driving wheel 10 (namely,
the right crawler belt 12) rotates when a right travel hydraulic
motor 13B is driven.
[0028] A blade 14 for earth removal is mounted on the front side of
the track frame 9 and can be moved up and down. A blade hydraulic
cylinder (not shown) is telescopically driven to move the blade 14
up and down.
[0029] A turning wheel 15 is disposed at the center of the track
frame 9. The turning frame 3 can be turned through the turning
wheel 15. The turning frame 3 (namely, the upper turning structure
2) turns when a turning hydraulic motor (not shown) is driven.
[0030] The swing post 4, which is mounted on the front side of the
turning frame 3 and can be turned in a left-right direction, turns
in the left-right direction when a swing hydraulic cylinder (not
shown) is telescopically driven. This causes the work machine 5 to
swing in the left-right direction.
[0031] The work machine 5 includes a boom 16, an arm 17, and a
bucket 18. The boom 16 is coupled to the swing post 4 and can be
pivoted in an up-down direction. The arm 17 is coupled to the boom
16 and can be pivoted in an up-down direction. The bucket 18 is
coupled to the arm 17 and can be pivoted in an up-down direction.
The boom 16, the arm 17, and the bucket 18 are pivoted in the
up-down direction by a boom hydraulic cylinder 19, an arm hydraulic
cylinder 20, and a bucket hydraulic cylinder 21. The bucket 18 can
be replaced, for instance, with an attachment (not shown) in which
an optional hydraulic actuator is incorporated.
[0032] The cab 6 includes a cab seat (seat) 22 on which the
operator sits. Left and right travel control levers 23A, 23B (only
the travel control lever 23A is shown in a later-referenced FIG.
3), which can be manipulated in a front-rear direction by a hand or
by a foot to specify the operations of the left and right travel
hydraulic motors 13A, 13B (namely, the left and right crawler belts
12, 12), are disposed in front of the cab seat 22. An optional
control pedal (not shown) is disposed on a base to the left of the
left travel control lever 23A. When manipulated in a left-right
direction, the optional control pedal specifies the operation of
the optional hydraulic actuator (namely, the attachment). A swing
control pedal (not shown) is disposed on a base to the right of the
right travel control lever 23B. When manipulated in a left-right
direction, the swing control pedal specifies the operation of the
swing hydraulic cylinder (namely, the swing post 4).
[0033] An arm/turning control lever 24A (not shown), which is a
cross-directional control lever, is disposed to the left of the cab
seat 22. The arm/swing control lever 24A specifies the operation of
the arm hydraulic cylinder 20 (namely, the arm 17) when manipulated
in a front-rear direction and specifies the operation of the
turning hydraulic motor (namely, the upper turning structure 2)
when manipulated in a left-right direction. A boom/bucket control
lever 24B, which is a cross-directional control lever, is disposed
to the right of the cab seat 22. The boom/bucket control lever 24B
specifies the operation of the boom hydraulic cylinder 19 (namely,
the boom 16) when manipulated in a front-rear direction and
specifies the operation of the bucket hydraulic cylinder 21
(namely, the bucket 18) when manipulated in a left-right direction.
A blade control lever (not shown) is disposed to the right of the
cab seat 22. The blade control lever specifies the operation of the
blade hydraulic cylinder (namely, the blade 14) when manipulated in
a front-rear direction.
[0034] A gate lock lever (not shown) is disposed to the left of the
cab seat 22 (namely, on a platform of the cab 6). The gate lock
lever is placed in either an unlock position (or more specifically,
a descent position for inhibiting the operator from getting into
and out of the cab 6) or a lock position (or more specifically, an
ascent position for permitting the operator to get into and out of
the cab 6). A key switch 25, a dial 26, a charge switch 27, a
selector switch 28, remaining amount indicators 29A, 29B (see
later-referenced FIGS. 4 and 5), and the like are disposed to the
right of the cab seat 22. A monitor 30 is disposed to the front
right of the cab seat 22.
[0035] FIG. 3 is a hydraulic circuit diagram illustrating the
configuration of a hydraulic drive device included in the
electrically-operated hydraulic excavator described above. FIG. 3
shows the configuration concerning the left travel hydraulic motor
13A and the boom hydraulic cylinder 19 as a representative
example.
[0036] Referring to FIG. 3, an electric motor 31, the battery
device 7, an inverter device 32, a hydraulic pump 33, a pilot pump
34, a hydraulic pilot type operating device 35, and a left travel
directional control valve 36 are provided. The battery device 7
serves as an electrical power source for the electric motor 31. The
inverter device 32 controls the electrical power supplied to the
electric motor 31 in order to control the drive of the electric
motor 31. The hydraulic pump 33 and the pilot pump 34 are driven by
the electric motor 31. The hydraulic pilot type operating device 35
includes the aforementioned left travel control lever 23A. The left
travel directional control valve 36 controls the flow of hydraulic
fluid from the hydraulic pump 33 to the left travel hydraulic motor
13A in accordance with the position of the left travel control
lever 23A, which is manipulated in a front-rear direction. Also, a
hydraulic pilot type operating device 37 and a boom directional
control valve 38 are provided. The hydraulic pilot type operating
device 37 includes the aforementioned boom/bucket control lever
24B. The boom directional control valve 38 controls the flow of
hydraulic fluid from the hydraulic pump 33 to the boom hydraulic
cylinder 19 in accordance with the position of the boom/bucket
control lever 24B, which is manipulated in a front-rear direction.
Although not shown, the configuration concerning the right travel
hydraulic motor 13B, the arm hydraulic cylinder 20, the bucket
hydraulic cylinder 21, the turning hydraulic motor, the swing
hydraulic cylinder, and the blade hydraulic cylinder is
substantially the same as described above.
[0037] The left travel directional control valve 36, the boom
directional control valve 38, and other directional control valves
(or more specifically, a right travel directional control valve, an
arm directional control valve, a bucket directional control valve,
a turning directional control valve, a swing directional control
valve, and a blade directional control valve, which are not shown,
are included) are of a center bypass type and provided with a
center bypass path that is positioned on a center bypass line 39.
The center bypass path of each directional control valve is
series-connected to the center bypass line 39. When the spool of a
directional control valve is in neutral position, the center bypass
path of the directional control valve is in communication with the
center bypass line 39. When the spool is moved to either the left
position or right position shown in FIG. 3, the center bypass path
is out of communication with the center bypass line 39. The
upstream end of the center bypass line 39 is connected to a
discharge line 40 of the hydraulic pump 33, whereas the downstream
end of the center bypass line 39 is connected to a tank line
41.
[0038] Further, the left travel directional control valve 36, the
boom directional control valve 38, and other directional control
valves each include a signal path that is positioned on a hydraulic
signal line 42. More specifically, the signal path of each
directional control valve is series-connected to the hydraulic
signal line 42. When the spool of a directional control valve is in
neutral position, the signal path of the directional control valve
is in communication with the hydraulic signal line 42. When the
spool is moved to either the left position or right position shown
in FIG. 3, the signal path is out of communication with the
hydraulic signal line 42. The upstream end of the hydraulic signal
line 42 is connected so that it branches off from a discharge line
43 of the pilot pump 34, whereas the downstream end of the
hydraulic signal line 42 is connected to the tank line 41. The
upstream end of the most upstream directional control valve 36 in
the hydraulic signal line 42 is provided with a fixed restrictor
44. A pressure switch 45 (operation detection means) is disposed
between the fixed restrictor 44 and the directional control valve
36. The pressure switch 45 introduces the hydraulic fluid on the
upstream side of the directional control valve 36. When the
introduced hydraulic fluid reaches a preselected threshold value,
the pressure switch 45 closes its contact. Thus, the pressure
switch 45 detects whether any of the directional control valves has
changed its position, that is, detects whether any of the hydraulic
actuators (or more specifically, the left and right travel
hydraulic motors 13A, 13B, the boom hydraulic cylinder 19, the arm
hydraulic cylinder 20, the bucket hydraulic cylinder 21, the
turning hydraulic motor, the switch hydraulic cylinder, and the
blade hydraulic cylinder) is operated. If any hydraulic actuator is
operated, the pressure switch 45 outputs an ON signal.
[0039] The left travel directional control valve 36 changes its
position in accordance with a pilot pressure exerted by the
operating device 35. The operating device 35 includes the
aforementioned left travel control lever 23A and a pair of
pressure-reducing valves (pilot valves not shown) that generate the
pilot pressure by using the discharge pressure of the pilot pump 34
as a source pressure in accordance with the position of the control
lever 23A, which is manipulated in a front-rear direction. When,
for instance, the control lever 23A is manipulated from the neutral
position into the front position, the pilot pressure generated by
one of the pilot valves in accordance with the amount of control
lever 23A manipulation is output to a pressure-receiving section of
the left travel directional control valve 36 that is disposed on
the right side of FIG. 3. The left travel directional control valve
36 is then placed in the right position shown in FIG. 3. This
causes the left travel hydraulic motor 13A to rotate in a forward
direction and the left driving wheel 10 and crawler belt 12 to
rotate in a forward direction. When, on the other hand, the control
lever 23A is manipulated from the neutral position into the rear
position, the pilot pressure generated by the other pilot valve in
accordance with the amount of control lever 23A manipulation is
output to a pressure-receiving section of the left travel
directional control valve 36 that is disposed on the left side of
FIG. 3. The left travel directional control valve 36 is then placed
in the left position shown in FIG. 3. This causes the left travel
hydraulic motor 13A to rotate in a rearward direction and the left
driving wheel 10 and crawler belt 12 to rotate in a rearward
direction.
[0040] The boom directional control valve 38 changes its position
in accordance with a pilot pressure exerted by the operating device
37. The operating device 37 includes, for example, the boom/bucket
control lever 24B and a pair of pilot valves (pilot valves not
shown) that generate the pilot pressure by using the discharge
pressure of the pilot pump 34 as a source pressure in accordance
with the position of the control lever 24B, which is manipulated in
a front-rear direction. When, for instance, the control lever 24B
is manipulated from the neutral position into the front position,
the pilot pressure generated by one of the pilot valves in
accordance with the amount of control lever 24B manipulation is
output to a pressure-receiving section of the boom directional
control valve 38 that is disposed on the right side of FIG. 3. The
boom directional control valve 38 is then placed in the right
position shown in FIG. 3. This causes the boom hydraulic cylinder
19 to contract and the boom 16 to descend. When, on the other hand,
the control lever 24B is manipulated into the rear position, the
pilot pressure generated by the other pilot valve in accordance
with the amount of control lever 24B manipulation is output to a
pressure-receiving section of the boom directional control valve 38
that is disposed on the left side of FIG. 3. The boom directional
control valve 38 is then placed in the left position shown in FIG.
3. This causes the boom hydraulic cylinder 19 to expand and the
boom 16 to ascend.
[0041] The discharge line 43 of the pilot pump 34 is provided with
a pilot relief valve (not shown) that keeps the discharge pressure
of the pilot pump 34 constant. Further, the discharge line 43 of
the pilot pump 34 is provided with a lock valve 46. The lock valve
46 changes its position in accordance with the operation of the
aforementioned lock lever. More specifically, a lock switch 47 (see
later-referenced FIG. 4) is provided. When the lock lever is in the
unlock position (the descent position), the lock switch 47 closes.
When the lock lever is in the lock position (the ascent position),
the lock switch 47 opens. When, for instance, the lock switch 47
closes, a solenoid section of the lock valve 46 is energized
through the lock switch 47 so that the lock valve 46 is placed in
the lower position shown in FIG. 3. The discharge line 43 of the
pilot pump 34 then goes into communication so that the discharge
pressure of the pilot pump 34 is introduced into the operating
devices 35, 37 and the like. When, on the other hand, the lock
switch 47 opens, the solenoid section of the lock valve 46 does not
become energized so that the force of a spring places the lock
valve 46 in the upper position shown in FIG. 3. This blocks the
communication of the discharge line 43 of the pilot pump 34.
Consequently, even when, for instance, the operating devices 35, 37
are operated, no hydraulic actuator operates because the pilot
pressure is not generated.
[0042] FIG. 4 is a block diagram illustrating the configuration of
the inverter device 32 and related equipment according to the
present embodiment.
[0043] Referring to FIG. 4, the inverter device 32 selectively
exercises battery charge control and motor drive control. The
battery charge control is exercised to supply electrical power
from, for example, an external commercial power source 48 to the
battery device 7 when a cable from the commercial power source 48
is connected. The motor drive control is exercised to generate AC
power based on DC power from the battery device 7 and supplies the
generated AC power to the electric motor 31.
[0044] The inverter device 32 includes a rectifier 49, a
step-up/step-down transformer 50, an inverter 51, a control change
switch (normally-open contact relay) 52A, a control change switch
(normally-open contact relay) 52B, and an arithmetic control
section 53. The rectifier 49 converts an AC voltage of 200 V, which
is supplied from the commercial power source 48, to a DC voltage
when the battery charge control is exercised. When the battery
charge control is exercised, the step-up/step-down transformer 50
functions as a step-down transformer to decrease a DC voltage from
the rectifier 49 and supply the decreased DC voltage to the battery
device 7. When, on the other hand, the motor drive control is
exercised, the step-up/step-down transformer 50 functions as a
step-up transformer to increase a DC voltage of approximately 200 V
from the battery device 7 to a voltage of approximately 300 V. The
inverter 51 generates an alternating current based on a direct
current from the step-up/step-down transformer 50 and supplies the
generated alternating current to the electric motor 31 when the
motor drive control is exercised. The control change switch 52A is
disposed between the rectifier 49 and the step-up/step-down
transformer 50. The control change switch 52B is disposed between
the step-up/step-down transformer 50 and the inverter 51.
[0045] The arithmetic control section 53 of the inverter device 32
inputs signals from, for example, the aforementioned key switch 25,
dial 26, charge switch 27, selector switch 28, pressure switch 45,
and lock switch 47 and can communicate with later-described battery
controllers 54A, 54B of the battery device 7. Further, the
arithmetic control section 53 controls the step-up/step-down
transformer 50, the inverter 51, and the control change switches
52A, 52B and outputs a display signal to the monitor 30.
[0046] The key switch 25 includes a key cylinder and a key, which
can be inserted into the key cylinder, and outputs a signal in
accordance with a position (OFF position, ON position, or START
position) into which the key is rotated. The dial 26 specifies a
target revolution speed for the electric motor 31, and outputs a
signal indicative of the target revolution speed designated by a
position into which the dial 26 is rotated. The charge switch 27
specifies whether or not to exercise the battery charge control
(turn ON or OFF a battery charge control function), and outputs a
signal in accordance with a position (OFF position or ON position)
in which the charge switch 27 is placed.
[0047] The arithmetic control section 53 of the inverter device 32
exercises the battery charge control when the key switch 25 is
found to be placed in the OFF position depending on whether a
signal is output from the key switch 25, the charge switch 27 is
found to be placed in the ON position depending on whether a signal
is output from the charge switch 27, and the cable from the
commercial power source 48 is found to be connected depending on
whether a signal is output from a cable connection detection
circuit (not shown). In other words, the arithmetic control section
53 exercises control to close the control change switch 52A and
open the control change switch 52B, and outputs an instruction to
the step-up/step-down transformer 50 to decrease the voltage. In
accordance with the instruction, the step-up/step-down transformer
50 decreases the DC voltage from the rectifier 49 and supplies the
decreased DC voltage to the battery device 7.
[0048] When, for instance, the charge switch 27 is found to be
placed in the OFF position depending on whether a signal is output
from the charge switch 27 while the battery device 7 is being
charged, the arithmetic control section 53 of the inverter device
32 outputs a stop instruction to the step-up/step-down transformer
50. In accordance with the stop instruction, the step-up/step-down
transformer 50 stops a charge process.
[0049] When, for instance, the key switch 25 is found to be placed
in the START position depending on whether a signal is output from
the key switch 25 and the lock lever is found to be placed in the
lock position depending on whether a signal is output from the lock
switch 47, the arithmetic control section 53 of the inverter device
32 initiates the motor drive control. In other words, the
arithmetic control section 53 exercises control to open the control
change switch 52A and close the control change switch 52B, and
outputs an instruction to the step-up/step-down transformer 50 to
increase the voltage. In accordance with the instruction, the
step-up/step-down transformer 50 increases a DC voltage of
approximately 200 V from the battery device 7 to a voltage of
approximately 300 V. The arithmetic control section 53 also outputs
an instruction indicative of a target revolution speed designated
by the dial 26 to the inverter 51. In accordance with the
instruction, the inverter 51 controls the voltage applied to the
electric motor 31 so that the actual revolution speed of the
electric motor 31 agrees with the target revolution speed.
[0050] When, for instance, all hydraulic actuators are found to be
deactivated depending on whether a signal is output from the
pressure switch 45 while the electric motor 31 is being driven and
a preselected period of time (e.g., 4 seconds) elapses in the above
state, the arithmetic control section 53 of the inverter device 32
outputs an instruction to the inverter 51 to indicate a preselected
low revolution speed (idle revolution speed). In accordance with
the instruction, the inverter 51 controls the voltage applied to
the electric motor 31 so that the actual revolution speed of the
electric motor 31 agrees with the preselected low revolution
speed.
[0051] When, for instance, the key switch 25 is found to be placed
in the OFF position depending on whether a signal is output from
the key switch 25 while the electric motor 31 is being driven, the
arithmetic control section 53 of the inverter device 32 outputs a
stop instruction to the inverter 51. In accordance with the stop
instruction, the inverter 51 stops the electric motor 31.
[0052] FIG. 5 is a block diagram illustrating the configuration of
the battery device 7 and related equipment, which are essential
parts of the present embodiment.
[0053] Referring to FIG. 5, the battery device 7 includes a first
battery system 56A and a second battery system 56B. The first
battery system 56A includes, for example, nine series-connected
batteries (namely, modules) 55 (only three representative batteries
are shown in FIG. 5). The second battery system 56B includes, for
example, nine series-connected batteries 55 (only three
representative batteries are shown in FIG. 5). The battery systems
56A, 56B are parallel-connected to each other and connected to the
step-up/step-down transformer 50 of the inverter device 32. The
battery device 7 also includes a first battery controller 54A,
which relates to the first battery system 56A, and a second battery
controller 54B, which relates to the second battery system 56B.
[0054] Although details are not shown, each battery 55 includes a
plurality of cells made, for instance, of lithium ions, and is
provided with a cell controller that monitors the cells. Each cell
controller in the first battery system 56A acquires information
about each battery 55 (or more specifically, the current, voltage,
temperature, and other state quantities) and outputs the acquired
information to the first battery controller 54A. Similarly, each
cell controller in the second battery system 56B acquires
information about each battery 55 and outputs the acquired
information to the second battery controller 54B.
[0055] The positive electrode side of the first battery system 56A
(the right side of FIG. 5) is provided with a first current sensor
57A and a first connection change switch (normally-open contact
relay) 58A. The positive electrode side of the second battery
system 56B (the right side of FIG. 5) is provided with a second
current sensor 57B and a second connection change switch
(normally-open contact relay) 58B. The first current sensor 57A
detects the current of the first battery system 56A and outputs the
detected current to the first battery controller 54A. Similarly,
the second current sensor 57B detects the current of the second
battery system 56B and outputs the detected current to the second
battery controller 54B.
[0056] The first battery controller 54A computes the amount of
electrical power remaining in the first battery system 56A in
accordance with the battery information (voltage, etc.) supplied
from a plurality of cell controllers and transmits the computed
value to the arithmetic control section 53 of the inverter device
32. The first battery controller 54A also determines the level of a
charge state indicated by the computed electrical power remaining
in the first battery system 56A on a scale, for instance, of ten
levels (in which, more specifically, level 0 represents a
fully-discharged state whereas level 10 represents a fully-charged
state), and outputs a display signal indicative of the determined
level to the remaining amount indicator 29A. The remaining amount
indicator 29A illuminates/extinguishes, for example, a 10-segment
bar to indicate the amount of electrical power remaining in the
first battery system 56A on a scale of ten levels.
[0057] Similarly, the second battery controller 54B computes the
amount of electrical power remaining in the second battery system
56B in accordance with the battery information (voltage, etc.)
supplied from a plurality of cell controllers and transmits the
computed value to the arithmetic control section 53 of the inverter
device 32. The second battery controller 54B also determines the
level of a charge state indicated by the computed electrical power
remaining in the second battery system 56B on a scale, for
instance, of ten levels and outputs a display signal indicative of
the determined level to the remaining amount indicator 29B. The
remaining amount indicator 29B illuminates/extinguishes, for
example, a 10-segment bar to indicate the amount of electrical
power remaining in the second battery system 56B on a scale of ten
levels.
[0058] Further, the first battery controller 54A determines in
accordance with the battery information from a plurality of cell
controllers whether the first battery system 56A is abnormal. If
the first battery system 56A is found to be abnormal, the first
battery controller 54A transmits an error signal to the arithmetic
control section 53 of the inverter device 32. Similarly, the second
battery controller 54B determines in accordance with the battery
information from a plurality of cell controllers whether the second
battery system 56B is abnormal. If the second battery system 56B is
found to be abnormal, the second battery controller 54B transmits
an error signal to the arithmetic control section 53 of the
inverter device 32.
[0059] A major feature of the present embodiment is that the
selector switch 28 (see earlier-referenced FIG. 4) selects either
one of the battery systems 56A, 56B in accordance with a manual
operation, and outputs a selection signal indicative of a position
selected by the manual operation. When, for instance, a selection
signal for the first battery system 56A is input from the selector
switch 28 while the motor drive control is being exercised, the
arithmetic control section 53 of the inverter device 32 exercises
control to close the first connection change switch 58A through the
first battery controller 54A and open the second connection change
switch 58B through the second battery controller 54B. This connects
the first battery system 56A to the step-up/step-down transformer
50 of the inverter device 32. Further, when, for instance, a
selection signal for the second battery system 56B is input from
the selector switch 28 while the motor drive control is being
exercised, the arithmetic control section 53 of the inverter device
32 exercises control to open the first connection change switch 58A
through the first battery controller 54A and close the second
connection change switch 58B through the second battery controller
54B. This connects the second battery system 56B to the
step-up/step-down transformer 50 of the inverter device 32.
[0060] The process for exercising the above-described battery
charge control will now be described with reference to FIG. 6. FIG.
6 is a flowchart illustrating the battery charge control process
according to the present embodiment.
[0061] Referring to FIG. 6, in step 100, the arithmetic control
section 53 of the inverter device 32 exercises control to close the
control change switch 52A and open the control change switch 52B.
Processing then proceeds to step 110. In step 110, if, for
instance, the first battery system 56A is selected by the selector
switch 28, the arithmetic control section 53 of the inverter device
32 transmits a close instruction signal to the first battery
controller 54A and transmits an open instruction signal to the
second battery controller 54B. In response to the transmitted
instruction signals, the first battery controller 54A exercises
control to close the first connection change switch 58A whereas the
second battery controller 54B exercises control to open the second
connection change switch 58B. This connects the first battery
system 56A to the step-up/step-down transformer 50 of the inverter
device 32. Next, processing proceeds to step 120. In step 120, the
arithmetic control section 53 of the inverter device 32 outputs an
instruction to the step-up/step-down transformer 50 to decrease the
voltage. The AC voltage of 200 V from the commercial power source
48 is then converted to a DC voltage by the rectifier 49. The
resulting DC voltage is decreased by the step-up/step-down
transformer 50 and supplied to the first battery system 56A to
charge the first battery system 56A.
[0062] In the above instance, the first current sensor 57A detects
the current of the first battery system 56A and transmits a
resulting detection signal to the arithmetic control section 53 of
the inverter device 32 through the first battery controller 54A.
Processing then proceeds to step 130. In step 130, the arithmetic
control section 53 of the inverter device 32 uses the
aforementioned detection signal to verify that the first battery
system 56A is being charged, and outputs a display signal for the
first battery system 56A to the monitor 30. Accordingly, the
monitor 30 indicates that the first battery system 56A is being
charged. While the first battery system 56A is being charged, the
first battery controller 54A successively computes the amount of
electrical power remaining in the first battery system 56A,
transmits the computed value to the arithmetic control section 53
of the inverter device 32, and causes the remaining amount
indicator 29A to display the computed value.
[0063] Next, processing proceeds to step 140. In step 140, the
arithmetic control section 53 of the inverter device 32 determines
whether the first battery system 56A is fully charged. If, for
instance, the first battery system 56A is not yet fully charged,
the condition in step 140 is not met. Therefore, the arithmetic
control section 53 continuously causes the first battery system 56A
to be charged until the condition is met. However, if an error
signal is received from the battery controller 54A or from the
battery controller 54B, the arithmetic control section 53 outputs a
stop instruction to the step-up/step-down transformer 50 to stop a
charge process. In this instance, the arithmetic control section 53
outputs an error display signal to the monitor 30 and outputs a
drive signal to a buzzer (not shown). This causes the monitor 30 to
illuminate its abnormality indicator lamp and the buzzer to
sound.
[0064] When, for instance, the first battery system 56A is fully
charged, the condition in step 140 is met so that processing
proceeds to step 150. In step 150, the arithmetic control section
53 of the inverter device 32 transmits an open instruction signal
to the first battery controller 54A and transmits a close
instruction signal to the second battery controller 54B. In
response to the transmitted instruction signals, the first battery
controller 54A exercises control to open the first connection
change switch 58A whereas the second battery controller 54B
exercises control to close the second connection change switch 58B.
This connects the second battery system 56B to the
step-up/step-down transformer 50 of the inverter device 32. Hence,
the AC voltage of 200 V from the commercial power source 48 is
converted to a DC voltage by the rectifier 49. The resulting DC
voltage is decreased by the step-up/step-down transformer 50 and
supplied to the second battery system 56B to charge the second
battery system 56B.
[0065] In the above instance, the second current sensor 57B detects
the current of the second battery system 56B and transmits a
resulting detection signal to the arithmetic control section 53 of
the inverter device 32 through the second battery controller 54B.
Processing then proceeds to step 160. In step 160, the arithmetic
control section 53 of the inverter device 32 uses the
aforementioned detection signal to verify that the second battery
system 56B is being charged, and outputs a display signal for the
second battery system 56B to the monitor 30. Accordingly, the
monitor 30 indicates that the second battery system 56B is being
charged. While the second battery system 56B is being charged, the
second battery controller 54B successively computes the amount of
electrical power remaining in the second battery system 56B,
transmits the computed value to the arithmetic control section 53
of the inverter device 32, and causes the remaining amount
indicator 29B to display the computed value.
[0066] Next, processing proceeds to step 170. In step 170, the
arithmetic control section 53 of the inverter device 32 determines
whether the second battery system 56B is fully charged. If, for
instance, the second battery system 56B is not yet fully charged,
the condition in step 170 is not met. Therefore, the arithmetic
control section 53 continuously causes the second battery system
56B to be charged until the condition is met. However, if an error
signal is received from the battery controller 54A or from the
battery controller 54B, the arithmetic control section 53 outputs a
stop instruction to the step-up/step-down transformer 50 to stop a
charge process. In this instance, the arithmetic control section 53
outputs an error display signal to the monitor 30 and outputs a
drive signal to the buzzer. This causes the monitor 30 to
illuminate its abnormality indicator lamp and the buzzer to
sound.
[0067] When, for instance, the second battery system 56B is fully
charged, the condition in step 170 is met so that processing
proceeds to step 180. In step 180, the arithmetic control section
53 of the inverter device 32 transmits an open instruction signal
to the second battery controller 54B. In response to the
transmitted instruction signal, the second battery controller 54B
exercises control to open the second connection change switch 58B.
This disconnects the battery systems 56A, 56B from the
step-up/step-down transformer 50 of the inverter device 32, thereby
terminating the battery charge control.
[0068] The process for exercising the above-described motor drive
control will now be described with reference to FIG. 7. FIG. 7 is a
flowchart illustrating the motor drive control process according to
the present embodiment.
[0069] Referring to FIG. 7, in step 200, the arithmetic control
section 53 of the inverter device 32 exercises control to open the
control change switch 52A and close the control change switch 52B.
Processing then proceeds to step 210. In step 210, if, for
instance, the first battery system 56A is selected by the selector
switch 28, the arithmetic control section 53 of the inverter device
32 transmits a close instruction signal to the first battery
controller 54A and transmits an open instruction signal to the
second battery controller 54B. In response to the transmitted
instruction signals, the first battery controller 54A exercises
control to close the first connection change switch 58A whereas the
second battery controller 54B exercises control to open the second
connection change switch 58B. This connects the first battery
system 56A to the step-up/step-down transformer 50 of the inverter
device 32. Next, processing proceeds to step 220. In step 220, the
arithmetic control section 53 of the inverter device 32 outputs an
instruction to the step-up/step-down transformer 50 to increase the
voltage. Processing then proceeds to step 230. In step 230, the
arithmetic control section 53 of the inverter device 32 outputs an
instruction indicative of a target revolution speed to the inverter
51. The DC voltage from the first battery system 56A is then
increased by the step-up/step-down transformer 50. Next, an AC
voltage is generated by the inverter 51 based on the increased DC
voltage and is supplied to the electric motor 31 to drive the
electric motor 31.
[0070] In the above instance, the first current sensor 57A detects
the current of the first battery system 56A and transmits a
resulting detection signal to the arithmetic control section 53 of
the inverter device 32 through the first battery controller 54A.
Processing then proceeds to step 240. In step 240, the arithmetic
control section 53 of the inverter device 32 uses the
aforementioned detection signal to verify that the first battery
system 56A is being discharged, and outputs a display signal for
the first battery system 56A to the monitor 30. Accordingly, the
monitor 30 indicates that the first battery system 56A is being
discharged. While the first battery system 56A is being discharged,
the first battery controller 54A successively computes the amount
of electrical power remaining in the first battery system 56A,
transmits the computed value to the arithmetic control section 53
of the inverter device 32, and causes the remaining amount
indicator 29A to display the computed value.
[0071] Next, processing proceeds to step 250. In step 250, the
arithmetic control section 53 of the inverter device 32 determines
whether no electrical power remains in the first battery system 56A
(that is, whether the first battery system 56A is fully
discharged). If, for instance, the first battery system 56A is not
yet fully discharged, the condition in step 250 is not met.
Therefore, the arithmetic control section 53 continuously causes
the electric motor 31 to be driven (that is, causes the first
battery system 56A to be discharged) until the condition is met.
However, if an error signal is received from the battery controller
54A or from the battery controller 54B, the arithmetic control
section 53 outputs a stop instruction to the step-up/step-down
transformer 50 and to the inverter 51 to stop the electric motor
31. In this instance, the arithmetic control section 53 outputs an
error display signal to the monitor 30 and outputs a drive signal
to the buzzer. This causes the monitor 30 to illuminate its
abnormality indicator lamp and the buzzer to sound.
[0072] When, for instance, the first battery system 56A is fully
discharged, the condition in step 250 is met so that processing
proceeds to step 260. In step 260, the arithmetic control section
53 of the inverter device 32 transmits a display signal to the
remaining amount indicator 29A through the first battery controller
54A to indicate that the first battery system 56A is fully
discharged. To give such an indication in accordance with the
display signal, the remaining amount indicator 29A, for example,
blinks only the both ends of the 10-segment bar. Processing then
proceeds to step 270. In step 270, the arithmetic control section
53 of the inverter device 32 outputs a stop instruction to the
inverter 51 to stop the electric motor 31 (motor stop means). In
this instance, a drive signal is output to the buzzer to sound the
buzzer.
[0073] Next, processing proceeds to step 280. In step 280, the
selection signal from the selector switch 28 is used to determine
whether the selector switch 28 is operated to select the second
battery system 56B. If, for instance, the selector switch 28 is not
operated and the second battery system 56B is not selected, the
condition in step 280 is not met. Therefore, processing returns to
step 270 to repeat the above-described steps.
[0074] When, for instance, the selector switch 28 is operated to
select the second battery system 56B, the condition in step 280 is
met so that processing proceeds to step 290. In step 290, the
arithmetic control section 53 of the inverter device 32 transmits
an open instruction signal to the first battery controller 54A and
transmits a close instruction signal to the second battery
controller 54B. In response to the transmitted instruction signals,
the first battery controller 54A exercises control to open the
first connection change switch 58A whereas the second battery
controller 54B exercises control to close the second connection
change switch 58B. This connects the second battery system 56B to
the step-up/step-down transformer 50 of the inverter device 32.
Next, processing proceeds to step 300. In step 300, an instruction
indicative of a target revolution speed is output to the inverter
51. Hence, the DC voltage from the second battery system 56B is
increased by the step-up/step-down transformer 50. An AC voltage is
then generated by the inverter 51 based on the increased DC voltage
and supplied to the electric motor 31 to drive the electric motor
31.
[0075] In the above instance, the second current sensor 57B detects
the current of the second battery system 56B and transmits a
resulting detection signal to the arithmetic control section 53 of
the inverter device 32 through the second battery controller 54B.
Processing then proceeds to step 310. In step 310, the arithmetic
control section 53 of the inverter device 32 uses the
aforementioned detection signal to verify that the second battery
system 56B is being discharged, and outputs a display signal for
the second battery system 56B to the monitor 30. Accordingly, the
monitor 30 indicates that the second battery system 56B is being
discharged. While the second battery system 56B is being
discharged, the second battery controller 54B successively computes
the amount of electrical power remaining in the second battery
system 56B, transmits the computed value to the arithmetic control
section 53 of the inverter device 32, and causes the remaining
amount indicator 29B to display the computed value.
[0076] In the present embodiment configured as described above, the
battery device 7 includes the two battery systems 56A, 56B so that
either one of them supplies electrical power to drive the electric
motor 31. In other words, only one battery system is used at a
time. Therefore, even if the electrically-operated hydraulic
excavator stops because the battery system supplying electrical
power to the electric motor 31 is exhausted without the knowledge
of the operator, the selector switch 28 can be manually operated to
switch to the other battery system and let the other battery system
supply electrical power to the electric motor 31. This makes it
possible to operate the electrically-operated hydraulic excavator.
Consequently, as the electrically-operated hydraulic excavator can
travel by using its battery power, it is possible to avoid a
situation where charging is difficult to achieve.
[0077] In the present embodiment, if a battery system supplying
electrical power to the electric motor 31 is exhausted, the
electrically-operated hydraulic excavator is stopped until the
operator operates the selector switch 28. This ensures that the
operator certainly becomes aware of the exhausted battery system.
Further, the operator can feel the length of time during which the
excavator is available, that is, the interval between the instant
at which a battery system is fully charged and the instant at which
it is fully discharged. Therefore, after switching from one battery
system to another, the operator can predict the maximum length of
time during which the currently selected battery system can be
used. This makes it possible to plan the timing of charging.
[0078] Furthermore, only one of the two battery systems 56A, 56B
can be fully charged to operate the electrically-operated hydraulic
excavator. This make is possible to reduce the time required for
charging. Moreover, the length of time of use and the number of
charge and discharge processes vary from one battery system to
another. This causes battery replacement periods to vary from one
battery system to another. Therefore, unlike the case where all the
batteries are series-connected so that their replacement periods
are the same, it is possible to decrease the number of batteries to
be replaced at a time and reduce the replacement cost of each
battery.
[0079] The foregoing preferred embodiment has been described on the
assumption that the connection status of each battery system 56A,
56B is changed in accordance with a manual operation of the
selector switch 28. However, the present invention is not limited
to such a battery system connection status change. For example, an
alternative is to stop the electric motor 31 when a battery system
supplying electrical power to the electric motor 31 is exhausted,
and then after the elapse of a preselected period of time,
automatically switch to another battery system. A motor drive
control process according to such a modified embodiment will now be
described with reference to FIG. 8. FIG. 8 is a flowchart
illustrating the motor drive control process according to the
modified embodiment. FIG. 9 is a block diagram illustrating the
configuration of an inverter device 32A and related equipment
according to the modified embodiment. Portions equal to those of
the foregoing preferred embodiment will not be redundantly
described.
[0080] In the modified embodiment, as is the case with the
foregoing preferred embodiment, an arithmetic control section 53A
of the inverter device 32A determines in step 250 whether the first
battery system 56A is exhausted (namely, fully discharged). If, for
instance, the first battery system 56A supplying electrical power
to the electric motor 31 is fully discharged, the condition in step
250 is met so that processing proceeds to step 260. In step 260,
the arithmetic control section 53A of the inverter device 32A
causes the remaining amount indicator 29A to indicate that the
first battery system 56A is fully discharged. The arithmetic
control section 53A of the inverter device 32A then proceeds to
step 270 and stops the electric motor 31. Next, the arithmetic
control section 53A of the inverter device 32A proceeds to step 320
and determines whether a preselected period of time has elapsed.
Before the elapse of the preselected period of time, the condition
in step 320 is not met so that the arithmetic control section 53A
of the inverter device 32A returns to step 270 and repeats the same
steps.
[0081] When the preselected period of time has elapsed, the
condition in step 320 is met so that processing proceeds to step
290. In step 290, the arithmetic control section 53A of the
inverter device 32A transmits an open instruction signal to the
first battery controller 54A and transmits a close instruction
signal to the second battery controller 54B. In response to the
transmitted instruction signals, the first battery controller 54A
exercises control to open the first connection change switch 58A
whereas the second battery controller 54B exercises control to
close the second connection change switch 58B. This connects the
second battery system 56B to the step-up/step-down transformer 50
of the inverter device 32A. Next, processing proceeds to step 300.
In step 300, an instruction indicative of a target revolution speed
is output to the inverter 51. Hence, the DC voltage from the second
battery system 56B is increased by the step-up/step-down
transformer 50. An AC voltage is then generated by the inverter 51
based on the increased DC voltage and supplied to the electric
motor 31.
[0082] The above-described modified embodiment also avoids a
situation where charging is difficult to achieve due to the
exhaustion of all batteries, as is the case with the foregoing
preferred embodiment. In addition, in the modified embodiment, the
electrically-operated hydraulic excavator remains stopped for a
predetermined period of time when a battery system supplying
electrical power to the electric motor 31 is exhausted. This
ensures that the operator certainly becomes aware of the exhausted
battery system.
[0083] Further, the battery device 7 according to the foregoing
preferred embodiment is configured so that the battery systems 56A,
56B have the same number of batteries 55. However, the present
invention is not limited to such a battery device configuration.
Alternatively, the battery systems 56A, 56B may differ in the
number of batteries 55. For example, the first battery system 56A
may include twelve series-connected batteries 55 whereas the second
battery system 56B may include six series-connected batteries 55.
Furthermore, the battery device 7 according to the foregoing
preferred embodiment has been described on the assumption that it
includes two battery systems 56A, 56B. However, the present
invention is not limited to such a battery device configuration.
Alternatively, the battery device 7 may include three or more
battery systems. For example, the battery device 7 may include
three battery systems that each have six series-connected batteries
55. The modified embodiment described above provides the same
advantages as the foregoing preferred embodiment.
[0084] In the foregoing description, it is assumed that the
electrically-operated hydraulic excavator includes, for instance,
the left and right travel hydraulic motors 13A, 13B and the turning
hydraulic motor as hydraulic actuators other than the work machine
hydraulic actuators (or more specifically, the boom hydraulic
cylinder 19, the arm hydraulic cylinder 20, and the bucket
hydraulic cylinder 21). However, the present invention is not
limited to such a configuration. For example, the
electrically-operated hydraulic excavator may include left and
right travel electric motors, which are driven by electrical power
supplied from the battery device 7, instead of the left and right
travel hydraulic motors 13A, 13B. Further, the
electrically-operated hydraulic excavator may include a turning
electric motor, which is driven by electrical power supplied from
the battery device 7, instead of the turning hydraulic motor. The
above-described modified embodiment also provides the same
advantages as the foregoing preferred embodiment. Moreover, it is
obvious that the present invention is applicable not only to the
electrically-operated hydraulic excavator but also to the other
electric construction machines.
DESCRIPTION OF REFERENCE NUMERALS
[0085] 7 . . . Battery device [0086] 13A . . . Left travel
hydraulic motor [0087] 13B . . . Right travel hydraulic motor
[0088] 19 . . . Boom hydraulic cylinder [0089] 20 . . . Arm
hydraulic cylinder [0090] 21 . . . Bucket hydraulic cylinder [0091]
28 . . . Selector switch (manual selection means) [0092] 30 . . .
Monitor (display means) [0093] 31 . . . Electric motor [0094] 32 .
. . Inverter device (connection change control means, motor stop
control means) [0095] 32A . . . Inverter device (connection change
control means, motor stop control means, automatic selection means)
[0096] 33 . . . Hydraulic pump [0097] 54A . . . First battery
controller (remaining battery power amount acquisition means)
[0098] 54B . . . Second battery controller (remaining battery power
amount acquisition means) [0099] 55 . . . Battery [0100] 56A . . .
First battery system [0101] 56B . . . Second battery system [0102]
58A . . . First connection change switch (connection change control
means) [0103] 58B . . . Second connection change switch (connection
change control means)
* * * * *