U.S. patent application number 09/911396 was filed with the patent office on 2002-03-14 for remaining charge detection device for power storage unit.
This patent application is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Araki, Kazuhiro, Maruno, Naoki, Yamada, Yasuo.
Application Number | 20020030494 09/911396 |
Document ID | / |
Family ID | 18723089 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020030494 |
Kind Code |
A1 |
Araki, Kazuhiro ; et
al. |
March 14, 2002 |
Remaining charge detection device for power storage unit
Abstract
A remaining charge detection device for a power storage unit
including a current detection unit which detects the current value
of a charging current and a discharging current of a power storage
unit; a voltage detection unit which detects the voltage value of a
terminal voltage of the power storage unit; and a current
accumulation remaining charge calculation means which accumulates
the current value detected by the current detection unit to obtain
an accumulated charging current and discharging current and
calculates a remaining charge of the power storage unit. The
remaining charge detection device further includes a no-load state
detection unit which detects a no-load state of the power storage
unit, and a remaining charge for calibration calculation unit which
calculates a remaining charge for calibration for the remaining
charge of the power storage unit.
Inventors: |
Araki, Kazuhiro; (Wako-shi,
JP) ; Maruno, Naoki; (Wako-shi, JP) ; Yamada,
Yasuo; (Wako-shi, JP) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN
1050 CONNECTICUT AVENUE, N.W.
SUITE 600
WASHINGTON
DC
20036
US
|
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha
|
Family ID: |
18723089 |
Appl. No.: |
09/911396 |
Filed: |
July 25, 2001 |
Current U.S.
Class: |
324/427 |
Current CPC
Class: |
G01R 31/374 20190101;
G01R 31/3828 20190101; G01R 31/3835 20190101; G01R 31/392
20190101 |
Class at
Publication: |
324/427 |
International
Class: |
G01N 027/416 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 28, 2000 |
JP |
P2000-230074 |
Claims
1. A remaining charge detection device for a power storage unit
including: a current detection unit which detects the current value
of a charging current and a discharging current of a power storage
unit; a voltage detection unit which detects the voltage value of a
terminal voltage of said power storage unit; and a current
accumulation remaining charge calculation means which accumulates
the current value detected by said current detection unit to obtain
an accumulated charging current and an accumulated discharging
current and, based on said accumulated charging current and said
accumulated discharging current, calculates a remaining charge of
said power storage unit, said remaining charge detection device
further comprising: a no-load state detection unit which detects a
no-load state of said power storage unit; and a remaining charge
for calibration calculation unit which calculates, according to the
voltage value detected in the no-load state of said power storage
unit, a remaining charge for calibration with respect to said
remaining charge of said power storage unit.
2. A remaining charge detection device for a power storage unit
according to claim 1, further comprising: a standard remaining
charge calibration unit which calibrates, based on said remaining
charge for calibration calculated by said remaining charge for
calibration calculation unit, a predetermined standard remaining
charge which may be used when said remaining charge of said power
storage unit is expressed as a percentage with respect to said
predetennined standard remaining charge.
3. A control device for a hybrid vehicle including an engine which
outputs a driving force for the hybrid vehicle, a motor which
assists an output of the engine in accordance with a driving state
of the hybrid vehicle, and a power storage unit which stores energy
generated by the motor used as a generator and regenerative energy
obtained by a regenerative operation of said motor when said hybrid
vehicle is decelerating, said control device for a hybrid vehicle
comprising: a remaining charge detection device for said power
storage unit, including: a current detection unit which detects the
current value of a charging current and a discharging current of
said power storage unit; a voltage detection unit which detects the
voltage value of a terminal voltage of said power storage unit; a
current accumulation remaining charge calculation means which
calculates the accumulation of the current value detected by said
current detection unit to obtain an accumulated charging current
and an accumulated discharging current and, based on said
accumulated charging current and said accumulated discharging
current, calculates a remaining charge of said power storage unit;
a no-load state generation unit which creates a no-load state of
said power storage unit by terminating the output assistance of
said engine by said motor and the regenerative operation of said
motor; a no-load state detection unit which detects the no-load
state of said power storage unit; and a remaining charge for
calibration calculation unit which calculates, according to the
voltage value detected in the no-load state of said power storage
unit, a remaining charge for calibration with respect to said
remaining charge of said power storage unit.
4. A control device for a hybrid vehicle according to claim 3,
wherein p1 said current accumulation remaining charge calculation
means calculates a remaining charge of said power storage unit
while said hybrid vehicle is in a running mode.
5. A control device for a hybrid vehicle according to claim 3,
further comprising: a remaining charge correction unit which
retains a predetermined remaining charge that has been set in
accordance with a predetermined voltage value, current value, and
temperature for said power storage unit, said remaining charge
correction unit being capable of setting, when said voltage value
detected by said voltage detection unit reaches said predetermined
voltage value, said predetermined remaining charge as said
remaining charge of said power storage unit, wherein said no-load
state generation unit creates the no-load state of said power
storage unit when said remaining charge of said power storage unit
is corrected by said remaining charge correction unit.
6. A control device for a hybrid vehicle according to claim 3,
further comprising: a remaining charge for correction calibration
unit which calibrates said predetermined remaining charge based on
said remaining charge for calibration calculated by said remaining
charge for calibration calculation unit.
7. A control device for a hybrid vehicle according to claim 3,
further comprising: a standard remaining charge calibration unit
which calibrates, based on said remaining charge for calibration
calculated by said remaining charge for calibration calculation
unit, a predetermined standard remaining charge which may be used
when said remaining charge of said power storage unit is expressed
as a percentage with respect to said predetermined standard
remaining charge.
8. A control device for a hybrid vehicle according to claim 4,
further comprising: a standard remaining charge calibration unit
which calibrates, based on said remaining charge for calibration
calculated by said remaining charge for calibration calculation
unit, a predetermined standard remaining charge which may be used
when said remaining charge of said power storage unit is expressed
as a percentage with respect to said predetermined standard
remaining charge.
9. A control device for a hybrid vehicle according to claim 5,
further comprising: a standard remaining charge calibration unit
which calibrates, based on said remaining charge for calibration
calculated by said remaining charge for calibration calculation
unit, a predetermined standard remaining charge which may be used
when said remaining charge of said power storage unit is expressed
as a percentage with respect to said predetermined standard
remaining charge.
10. A control device for a hybrid vehicle according to claim 6,
further comprising: a standard remaining charge calibration unit
which calibrates, based on said remaining charge for calibration
calculated by said remaining charge for calibration calculation
unit, a predetermined standard remaining charge which may be used
when said remaining charge of said power storage unit is expressed
as a percentage with respect to said predetermined standard
remaining charge.
11. A hybrid vehicle provided with a remaining charge detection
device for a power storage unit including: a current detection unit
which detects the current value of a charging current and a
discharging current of a power storage unit; a voltage detection
unit which detects the voltage value of a terminal voltage of said
power storage unit; and a current accumulation remaining charge
calculation means which accumulates the current value detected by
said current detection unit to obtain an accumulated charging
current and an accumulated discharging current and, based on said
accumulated charging current and said accumulated discharging
current, calculates a remaining charge of said power storage unit,
said remaining charge detection device further comprising: a
no-load state detection unit which detects a no-load state of said
power storage unit; and a remaining charge for calibration
calculation unit which calculates, according to the voltage value
detected in the no-load state of said power storage unit, a
remaining charge for calibration with respect to said remaining
charge of said power storage unit.
12. A hybrid vehicle according to claim 11, wherein said remaining
charge detection device for a power storage unit further
comprising: a standard remaining charge calibration unit which
calibrates, based on said remaining charge for calibration
calculated by said remaining charge for calibration calculation
unit, a predetermined standard remaining charge which may be used
when said remaining charge of said power storage unit is expressed
as a percentage with respect to said predetermined standard
remaining charge.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a remaining charge
detection device for a power storage unit, such as a battery. More
specifically, the present invention relates to a remaining charge
detection device for a power storage unit, which utilizes a
technique of calibrating the remaining charge calculated based on a
current accumulation method.
[0003] 2. Description of Related Art
[0004] As a method for detecting the remaining charge of a power
storage unit (e.g., a battery) which is provided in, for instance,
a hybrid car, one is generally known in which the accumulated
charge amount and the accumulated discharge amount of the battery
are calculated by estimating the charging current and the
discharging current of the battery for each given period of time,
and adding or subtracting the accumulated charge amount/the
accumulated discharge amount to/from the initial charge or the
remaining charge of the battery prior to the charging-discharging
processes, since the remaining charge of the battery corresponds to
the total amount of electric charge retained in the battery.
[0005] However, in the above-mentioned method, for instance,
measurement errors in the current detector accumulate when the
accumulated charge amount and the accumulated discharge amount are
calculated, and errors contained in the calculated remaining charge
may be increased.
[0006] Because of the problems described above, as a remaining
charge detection device for a battery, which is capable of
calibrating the remaining charge calculated based on the
above-mentioned current accumulation method to an accurate value at
a suitable timing, Japanese Unexamined Patent Application, First
Publication No. 10-132911, for instance, discloses a battery
remaining charge detector in which predetermined relational
expressions or maps for current values, voltage values, and
remaining charges for the battery are stored. The battery remaining
charge detector calculates the remaining charge of the battery
based on the current value and the voltage value of the
charging/discharging current of the battery detected by a current
detector and a voltage detector, respectively, and carries out a
calibration of the calculated remaining charge based on the stored
relational expressions or maps.
[0007] However, since the predetermined relational expressions or
maps retained in the above-mentioned battery remaining charge
detector are prepared based on the voltage characteristic of a
battery in its stationary state (i.e., the battery has not
deteriorated), there is a difference between the actual remaining
charge of the battery and the remaining charge of the battery
calculated based on the predetermined maps or relational
expressions, and the difference may be increased when the internal
resistance of the battery is increased by, for instance, the
deterioration of the battery. If a value which contains an error is
detected as the remaining charge of a battery, the battery may be
used exceeding its limit and the life of the battery may be
shortened.
[0008] Also, when the remaining charge of a battery is defined as a
percentage with respect to a predetermined standard charge of the
battery and such a percentage value is used for controlling a motor
or an engine, problems may arise in controlling the motor or engine
and they may not be properly controlled if the degree of
deterioration of the battery is not reflected to the standard
charge of the battery.
SUMMARY OF THE INVENTION
[0009] The present invention is achieved in consideration of the
above situation, and its objectives include the provision of a
remaining charge detection device for a power storage unit, which
enables calculation, even if the power storage unit has
deteriorated, of an accurate remaining charge thereof based on an
accumulated charge amount and an accumulated discharge amount
obtained by estimating a charging current and a discharging
current.
[0010] Accordingly, the present invention provides a remaining
charge detection device for a power storage unit (for instance, a
battery 14 in an embodiment of the invention which will be
described later) including: a current detection unit (for instance,
a current detector 26 in an embodiment of the invention which will
be described later) which detects the current value of a charging
current and a discharging current of a power storage unit; a
voltage detection unit (for instance, a voltage detector 28 in an
embodiment of the invention which will be described later) which
detects the voltage value of a terminal voltage of the power
storage unit; and a current accumulation remaining charge
calculation means (for instance, step S02 in an embodiment of the
invention which will be described later) which accumulates the
current value detected by the current detection unit to obtain an
accumulated charging current and an accumulated discharging current
and, based on the accumulated charging current and the accumulated
discharging current, calculates a remaining charge (for instance, a
detected remaining charge SOC in an embodiment of the invention
which will be described later) of the power storage unit; wherein
the remaining charge detection device further includes: a no-load
state detection unit (for instance, a current consumer releasing
unit 23 in an embodiment of the invention which will be described
later) which detects a no-load state of the power storage unit; and
a remaining charge for calibration calculation unit (for instance,
a remaining charge for calibration calculation unit 25 in an
embodiment of the invention which will be described later) which
calculates, according to the voltage value detected in the no-load
state of the power storage unit (for instance, OCV in an embodiment
of the invention which will be described later), a remaining charge
for calibration (for instance, a remaining charge SOC.sub.OCV in an
embodiment of the invention which will be described later) with
respect to the remaining charge of the power storage unit.
[0011] According to the above remaining charge detection device for
a power storage unit, the upper limit and the lower limit of the
remaining charge of the power storage unit are determined, for
instance, from the viewpoint of protecting the power storage unit,
so that the remaining charge calculated by the current accumulation
method varies within a predetermined range. Also, predetermined
map(s) which show the relationships between the temperature,
current, and voltage of the power storage unit corresponding to the
upper limit and the lower limit of the remaining charge are
provided. The maps are constructed based on a stationary state of
the power storage unit having no deterioration, e.g., based on the
initial state of the power storage unit.
[0012] When an internal resistance of the power storage unit
increases due to such factors as the deterioration thereof, it may
be erroneously determined that the actual remaining charge of the
power storage unit has reached the upper limit, which, in fact, it
has not, because the detected terminal voltage of the power storage
unit has reached the upper limit voltage corresponding to the map
of the upper limit remaining charge. According to the present
invention, however, a no-load state of the power storage unit is
forcibly created by disconnecting the load, such as a motor, from
the power storage unit at this stage, and the terminal voltage at
the load-release state is measured after a certain period of time.
The characteristics of the remaining charge with respect to the
terminal voltage at the load-release state are not related to the
deterioration of the power storage unit, i.e., the increase in the
internal resistance thereof, and they are almost the same as those
in a power storage unit having no deterioration, e.g., at the
initial state thereof. For this reason, the remaining charge of the
power storage unit may be obtained with high accuracy by providing
a predetermined relational expression or map which shows the
relationship between the terminal voltage and the remaining charge
at the load-release state, and by searching the relational
expression or map.
[0013] In this manner, it becomes possible to calibrate the
remaining charge detected at the load-connected state by using the
remaining charge which is accurately detected at the load-release
state. Accordingly, the remaining charge may be calculated with
high accuracy even if the power storage unit is in the
load-connected state by setting, for instance, correction
coefficients for calibration.
[0014] In accordance with another aspect of the invention, the
remaining charge detection device for a power storage unit further
includes a standard remaining charge calibration unit (for
instance, a remaining charge correction unit 22 in an embodiment of
the invention which will be described later) which calibrates,
based on the remaining charge for calibration calculated by the
remaining charge for calibration calculation unit, a predetermined
standard remaining charge (for instance, a standard charge SOCf in
an embodiment of the invention which will be described later) which
may be used when the remaining charge of the power storage unit is
expressed as a percentage with respect to the predetermined
standard remaining charge.
[0015] The present invention also provides a control device for a
hybrid vehicle including an engine (for instance, an engine 12 in
an embodiment of the invention which will be described later) which
outputs a driving force for the hybrid vehicle, a motor (for
instance, a motor 11 in an embodiment of the invention which will
be described later) which assists an output of the engine in
accordance with a driving state of the hybrid vehicle, and a power
storage unit which stores energy generated by the motor used as a
generator and regenerative energy obtained by the regenerative
operation of the motor when the hybrid vehicle decelerates, wherein
the control device for a hybrid vehicle includes a remaining charge
detection device for the power storage unit, having a current
detection unit which detects the current value of a charging
current and a discharging current of the power storage unit, a
voltage detection unit which detects the voltage value of a
terminal voltage of the power storage unit, a current accumulation
remaining charge calculation means which accumulates the current
value detected by the current detection unit to obtain an
accumulated charging current and an accumulated discharging current
and, based on the accumulated charging current and the accumulated
discharging current, calculates a remaining charge of the power
storage unit, a no-load state generation unit (for instance, a
current consumer releasing unit 23 in an embodiment of the
invention which will be described later) which creates a no-load
state for the power storage unit by terminating the output
assistance for the engine by the motor and the regenerative
operation of the motor; a no-load state detection unit (for
instance, also a current consumer releasing unit 23 in an
embodiment of the invention which will be described later) which
detects the no-load state of the power storage unit; and a
remaining charge for calibration calculation unit which calculates,
according to the voltage value detected in the no-load state of the
power storage unit, a remaining charge for calibration with respect
to the remaining charge of the power storage unit.
[0016] According to the above control device for a hybrid vehicle,
it becomes possible to generate a no-load state of the power
storage unit by forcibly creating a state in which the output
assistance level and the amount of power regeneration are decreased
to zero by inhibiting an output assist operation for the engine by
the motor or a regeneration operation of the motor when a hybrid
vehicle is decelerated.
[0017] In accordance with another aspect of the invention, the
current accumulation remaining charge calculation means calculates
a remaining charge of the power storage unit while the hybrid
vehicle is in a running mode.
[0018] In accordance with another aspect of the invention, the
control device for a hybrid vehicle further includes a remaining
charge correction unit (for instance, a correction determination
voltage calculation unit 21 in an embodiment of the invention which
will be described later) which retains a predetermined remaining
charge (for instance, an upper limit remaining charge SOC.sub.MAP
and a lower limit remaining charge SOC.sub.MAP in an embodiment of
the invention which will be described later) that has been set in
accordance with a predetermined voltage value (for instance, a
voltage value V, an upper limit map voltage value Vmu, or a lower
limit map voltage value Vmd in an embodiment of the invention which
will be described later), current value (for instance, a current
value I in an embodiment of the invention which will be described
later), and temperature (for instance, a temperature T in an
embodiment of the invention which will be described later) for the
power storage unit, the remaining charge correction unit being
capable of setting, when the voltage value detected by the voltage
detection unit reaches the predetermined voltage value (for
instance, the upper limit map voltage value Vmu or the lower limit
map voltage value Vmd in an embodiment of the invention which will
be described later), the predetermined remaining charge as the
remaining charge of the power storage unit, wherein the no-load
state generation unit creates the no-load state for the power
storage unit when the remaining charge of the power storage unit is
corrected by the remaining charge correction unit.
[0019] According to the above control device for a hybrid vehicle,
a predetermined map for correcting the remaining charge is prepared
for correcting the remaining charge calculated by the current
accumulation method, and when the condition of the power storage
unit is matched with a condition indicated in the map for
correcting the remaining charge, a no-load state for the power
storage unit may be forcibly generated.
[0020] That is, the map for correcting the remaining charge is set
for a predetermined remaining charge and, for instance, when the
detected value of the terminal voltage of the power storage unit
reaches a predetermined voltage value which is set by the map for
correcting the remaining charge, a no-load state may be forcibly
created in the hybrid vehicle by decreasing the level of output
assistance for the engine and the amount of power regeneration to
zero. After a certain period of time which is required for
stabilizing the no-load state of the power storage unit, the
remaining charge of the power storage unit is calculated based on
the terminal voltage thereof in the no-load state, and the
remaining charge calculated by the current accumulation method is
calibrated by using the remaining charge in the no-load state.
[0021] In this manner, it becomes possible to avoid stopping the
engine output assistance or the regeneration operation of the motor
while the vehicle is running, and therefore, to prevent
uncomfortableness in driving the vehicle.
[0022] In yet another aspect of the invention, the control device
for a hybrid vehicle further includes a remaining charge for
correction calibration unit (for instance, a remaining charge
correction unit 22 in an embodiment of the invention which will be
described later) which calibrates the predetermined remaining
charge based on the remaining charge for calibration calculated by
the remaining charge for calibration calculation unit.
[0023] According to the above control device for a hybrid vehicle,
the predetermined remaining charge with respect to the remaining
charge correction map is calibrated based on the remaining charge
in the no-load state. That is, a correction coefficient is
calculated based on the remaining charge in the no-load state and
the predetermined remaining charge with respect to the remaining
charge correction map, and the correction coefficient is applied
to, for instance, the voltage value with respect to the remaining
charge correction map to renew the remaining charge correction map.
For example, for the remaining charge correction map which is set
for a predetermined upper limit remaining charge, the correction
coefficient may be applied to the upper limit voltage so that the
upper limit voltage is increased corresponding to the deterioration
of the power storage unit caused by, for instance, the increase in
the internal resistance thereof. In this manner, it becomes
possible to accurately detect the remaining charge of the power
storage unit by, for instance, preventing the detected terminal
voltage from reaching the upper limit voltage before the actual
remaining charge of the power storage unit reaches the
predetermined upper limit remaining charge.
[0024] In yet another aspect of the invention, the control device
for a hybrid vehicle further includes a standard remaining charge
calibration unit (for instance, also the remaining charge
correction unit 22 in an embodiment of the invention which will be
described later) which calibrates, based on the remaining charge
for calibration calculated by the remaining charge for calibration
calculation unit, a predetermined standard remaining charge (for
instance, a standard charge SOCf in an embodiment of the invention
which will be described later) which may be used when the remaining
charge of the power storage unit is expressed as a percentage with
respect to the predetermined standard remaining charge.
[0025] According to the above control device for a hybrid vehicle,
when the remaining charge of the power storage unit is expressed as
a percentage with respect to the predetermined standard remaining
charge, i.e., as a relative value, from the viewpoint of
comfortableness in controlling devices, such as a motor or an
engine, which are driven by electric power supplied from the power
storage unit, a correction coefficient is calculated based on the
remaining charge in the no-load state and the predetermined
remaining charge with respect to the remaining charge correction
map and applied to the standard charge. In this manner, it becomes
possible to accurately calculate the remaining charge of the power
storage unit regardless of the increase in the internal resistance
associated with the deterioration of the power storage unit when,
for instance, a remaining charge which is calculated by a current
accumulation is expressed as a percentage with respect to the
standard charge.
[0026] The present invention also provides a hybrid vehicle
provided with a remaining charge detection device for a power
storage unit. The remaining charge detection device includes a
current detection unit which detects the current value of a
charging current and a discharging current of a power storage unit;
a voltage detection unit which detects the voltage value of a
terminal voltage of the power storage unit; and a current
accumulation remaining charge calculation means which calculates
the accumulation of the current value detected by the current
detection unit to obtain an accumulated charging current and an
accumulated discharging current and, based on the accumulated
charging current and the accumulated discharging current,
calculates a remaining charge of the power storage unit. The
remaining charge detection device further includes a no-load state
detection unit which detects a no-load state of the power storage
unit; and a remaining charge for calibration calculation unit which
calculates, according to the voltage value detected in the no-load
state of the power storage unit, a remaining charge for calibration
with respect to the remaining charge of the power storage unit.
[0027] In accordance with another aspect of the invention, the
remaining charge detection device for a power storage unit of a
hybrid vehicle further includes a standard remaining charge
calibration unit which calibrates, based on the remaining charge
for calibration calculated by the remaining charge for calibration
calculation unit, a predetermined standard remaining charge which
may be used when the remaining charge of the power storage unit is
expressed as a percentage with respect to the predetermined
standard remaining charge.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Some of the features and advantages of the invention have
been described, and others will become apparent from the detailed
description that follows and from the accompanying drawings, in
which:
[0029] FIG. 1 is a block diagram showing the schematic
configuration of a remaining charge detection device for a power
storage unit according to an embodiment of the invention;
[0030] FIG. 2 is a flowchart for showing an operation of the
remaining charge detection device shown in FIG. 1;
[0031] FIG. 3A is a graph showing changes in the level of
regeneration when a current accumulation remaining charge SOC.sub.I
is corrected with respect to, for instance, a battery in which a
charging state has been maintained since the initial state
thereof;
[0032] FIG. 3B is a graph showing changes in the terminal voltage
when a current accumulation remaining charge SOC.sub.I is corrected
with respect to, for instance, a battery in which a charging state
has been maintained since the initial state thereof; and
[0033] FIG. 3C is a graph showing changes in the remaining charge
when a current accumulation remaining charge SOC.sub.I is corrected
with respect to, for instance, a battery in which a charging state
has been maintained since the initial state thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The invention summarized above and defined by the enumerated
claims may be better understood by referring to the following
detailed description, which should be read with reference to the
accompanying drawings. This detailed description of a particular
preferred embodiment, set out below to enable one to build and use
one particular implementation of the invention, is not intended to
limit the enumerated claims, but to serve as a particular example
thereof.
[0035] FIG. 1 is a block diagram showing the schematic
configuration of a remaining charge detection device 10 for a power
storage unit according to an embodiment of the invention.
[0036] The remaining charge detection device 10 for a power storage
unit according to this embodiment of the invention (hereinafter
simply referred to as the remaining charge detection device 10) may
be used, for instance, for a hybrid vehicle and, as shown in FIG.
1, may be connected to a hybrid control unit 13 which controls a
motor 11 and an engine 12. The remaining charge detection device 10
detects the remaining charge of a power storage unit, such as a
battery 14, which stores energy generated by the motor 11 used as a
generator and regenerative energy obtained by a regenerative
operation of the motor 11 when the vehicle is decelerating.
[0037] The remaining charge detection device 10 includes a
deterioration determination unit 20, a correction determination
voltage calculation unit 21, a remaining charge correction unit 22,
a current consumer releasing unit 23, an internal resistance
calculation unit 24, and a remaining charge for calibration
calculation unit 25. The remaining charge detection device 10, for
instance, estimates the charging current and the discharging
current of the battery 14 to calculate the accumulated charge
amount and the accumulated discharge amount, and carries out a
calibration process for the remaining charge (i.e., the current
accumulation remaining charge SOC.sub.I) of the battery 14, which
is obtained by adding/subtracting the accumulated charge amount and
the accumulated discharge amount to/from the initial remaining
charge/the remaining charge just before the charging- discharging
process (i.e., the initial detection SOCi). The remaining charge
detection device 10 then outputs the signal of the calibrated
remaining charge to, for instance, the hybrid control unit 13 or a
remaining charge display device (not shown in the figure) provided
with a display panel for an occupant.
[0038] The remaining charge detection device 10 according to an
embodiment of the present invention receives a signal of the
current value I output from a current detector 26 which detects the
discharging current supplied from the battery 14 to a load member,
such as the motor 11 and a generator, and the charging current
supplied from a loading device to the battery 14, a signal of the
temperature T output from a temperature detector 27 which detects
the temperature of the battery 14, and a signal of the voltage
value V output from a voltage detector 28 which detects the
terminal voltage Vb of the battery 14.
[0039] Note that the remaining charge detection device 10 includes
a memory unit 29 which stores a deterioration correction
coefficient .alpha. that is referred to when the calibration of the
current accumulation remaining charge SOC.sub.I is carried out.
[0040] The deterioration determination unit 20, as will be
described later, determines the deterioration of the battery 14 by
determining if the difference between a remaining charge
SOC.sub.OCV calculated for the battery 14 in the no-load state and
the remaining charge thereof with respect to predetermined
remaining charge correction maps (for instance, an upper limit
remaining charge SOC.sub.MAP and a lower limit remaining charge
SOC.sub.MAP) exceeding a predetermined threshold value.
[0041] The correction determination voltage calculation unit 21
includes a remaining charge correction map which is, for instance,
prepared by using the voltage characteristic of the battery 14 at a
stationary state and without any deterioration (e.g., at an initial
state thereof), i.e., a map showing the relationship among the
current value I, the voltage value V, and the temperature T at a
predetermined remaining charge of the battery 14.
[0042] Also, the correction determination voltage calculation unit
21, for instance, refers to each remaining charge correction map
for the predetermined upper limit remaining charge SOC.sub.MAP and
the lower limit remaining charge SOC.sub.MAP, which are provided
from the viewpoint of protecting and prolonging the life of the
battery 14, and obtains, by searching the map, an upper limit map
voltage value Vmu, at which the current accumulation remaining
charge SOC.sub.I calculated by the current accumulation method
reaches a predetermined upper limit remaining charge SOC.sub.MAP,
and a lower limit map voltage value Vmd, at which the current
accumulation remaining charge SOC.sub.I reaches a predetermined
lower limit remaining charge SOC.sub.MAP.
[0043] The remaining charge correction unit 22 carries out a
correction operation of the current accumulation remaining charge
SOC.sub.I based on the remaining charge for calibration calculated
by the remaining charge for calibration calculation unit 25 (which
will be described later), i.e., based on the remaining charge
SOC.sub.OCV in the no-load state.
[0044] The current consumer releasing unit 23 forcibly creates the
no-load state of the battery 14, for instance, in a hybrid vehicle,
by decreasing an output assistance level for the engine 12 by the
motor 11 and the amount of regenerative power generation by the
motor 11 to zero.
[0045] The internal resistance calculation unit 24, as will be
described later, corrects the internal resistance R which is
increased by the deterioration of the battery 14 by using the
deterioration correction coefficient .alpha. which is determined
based on the remaining charge SOC.sub.OCV in the no-load state and
the predetermined upper limit remaining charge SOC.sub.MAP or the
lower limit remaining charge SOC.sub.MAP with respect to the
remaining charge correction map.
[0046] The remaining charge for calibration calculation unit 25
calculates the remaining charge SOC.sub.OCV in the no-load state
based on the terminal voltage OCV of the battery 14 in the no-load
state, by searching a map showing the relationship between the
terminal voltage OCV and the remaining charge SOC.sub.OCV, which is
prepared, for instance, by using the voltage characteristic of the
battery 14 in the no-load state without any deterioration (e.g., at
an initial state thereof).
[0047] Next, operation of the remaining charge detection device 10
for a power storage unit according to an embodiment of the present
invention having the above-mentioned structure will be explained
with reference to the attached drawings.
[0048] FIG. 2 is a flowchart for showing the operation of the
remaining charge detection device 10. FIGS. 3A through 3C are
graphs showing changes in the level of regeneration (FIG. 3A),
changes in the terminal voltage (FIG. 3B), and changes in the
remaining charge (FIG. 3C) when the current accumulation remaining
charge SOC.sub.I is corrected with respect to, for instance, the
battery 14 in which a charging state has been maintained since the
initial state thereof.
[0049] In the remaining charge calculation process shown in FIG. 2,
a series of steps may be started, for instance, by turning on the
ignition switch to start the engine 12.
[0050] In step S01, the deterioration correction coefficient
.alpha. is read from the memory unit 29. Note that "1" may be set
as the initial value of the deterioration correction coefficient
.alpha. for the first process of the battery 14 (i.e., in its
initial state, etc.).
[0051] Next in step S02, an ampere-hour current Ah (for instance, a
positive value with respect to the charging current), which
includes the accumulated charge amount and the accumulated
discharge amount, is calculated by estimating, for instance, the
current value I of the charging current and the discharging current
of the battery 14 using the equation (1) shown below. The
ampere-hour current Ah may be expressed as a percentage with
respect to the standard charge SOCf, which will be described later,
and added to the initial state of the battery 14 or the remaining
charge of the battery 14 detected just before the
charging-discharging operation, i.e., the initial detection value
SOCi, to obtain the detected remaining charge SOC.
SOC=SOCi+Ah.times.100/SOCf (1)
[0052] Note that the standard charge SOCf is a value which is
obtained by multiplying a rated charge SOCr of the battery 14 by
the deterioration correction coefficient .alpha., as will be
described later. The standard charge SOCf is equal to the rated
charge SOCr when the battery 14 is in a non-deteriorated state.
[0053] In step S03, the terminal voltage Vb of the battery 14 is
detected by the voltage detector 28.
[0054] In step S04, it is determined if the battery 14 is in its
charging state or discharging state.
[0055] If it is determined that the battery 14 is in its charging
state, the process proceeds to step S05. On the other hand, if it
is determined that the battery 14 is in its discharging state, the
process proceeds to step S14, which will be described later.
[0056] In step S05, the upper limit map voltage value Vmu is
calculated by searching the upper limit remaining charge map which
is set for the predetermined upper limit remaining charge
SOC.sub.MAP. In this case, as shown in the equation (2) below, the
value of the upper limit map voltage value Vmu, for example, is
varied so as to correspond to the increase in the internal
resistance R associated with the deterioration of the battery 14 by
multiplying the internal resistance R by an inverse of the
deterioration correction coefficient a so that the deterioration
correction coefficient a is reflected in the upper limit map
voltage value Vmu. Note that in equation (2), the current value I
indicates the charging current.
Vmu=OCV-I.times.R/.alpha. (2)
[0057] Next, in step S06, it is determined if the terminal voltage
Vb of the battery 14 is greater than the upper limit map voltage
Vmu.
[0058] If the result of the determination is "YES", then the
process proceeds to step S07 whereas if the result of the
determination is "NO", then the operation described in step S02 and
thereafter will be carried out.
[0059] In step S07, a forcible loading process is carried out for a
predetermined period of time (for instance, one second). That is,
in a hybrid vehicle, for instance, the amount of regenerative power
generation is decreased to zero, and the no-load state of the
battery 14 is forcibly created.
[0060] Next, in step S08, the terminal voltage OCV of the battery
14 in the no-load state is measured.
[0061] In step S09, based on the detected terminal voltage OCV of
the battery 14 in the no-load state, for instance, the remaining
charge SOC.sub.OCV in the no-load state is calculated by searching
the map which is prepared based on the voltage characteristic of
the battery 14 in the no-load state (i.e., the battery 14 is
without any deterioration (e.g., in the initial state thereof)).
The map shows the relationship between the terminal voltage OCV and
the remaining charge SOC.sub.OCV.
[0062] In step S10, it is determined if the absolute value of the
difference between the detected remaining charge SOC and the
remaining charge SOC.sub.OCV in the no-load state is greater than a
predetermined value (for instance, 5%).
[0063] If the determination result is "YES", then the process
proceeds to step S11. On the other hand, if the determination
result is "NO", then the operation described in step S02 and
thereafter will be performed.
[0064] Next, in step S11, a value obtained by dividing the
remaining charge SOC.sub.OCV in the no-load state by the
predetermined upper limit remaining charge SOC.sub.MAP with respect
to the upper limit remaining charge map, or by the predetermined
lower limit remaining charge SOC.sub.MAP with respect to the lower
limit remaining charge map, is set as the deterioration correction
coefficient .alpha..
[0065] Then, in step S12, the obtained deterioration correction
coefficient .alpha. is stored in the memory unit 29.
[0066] In step S13, a value obtained by multiplying the rated
charge SOCr of the battery 14 by the deterioration correction
coefficient .alpha. is set as the standard charge SOCf, and the
series of above-mentioned operations are terminated.
[0067] On the other hand, in step S14, the lower limit map voltage
Vmd is calculated by searching the lower limit remaining charge map
which is set for the predetermined lower limit remaining charge
SOC.sub.MAP. In this case, as shown in the equation (3) below, for
instance, the value of the lower limit map voltage value Vmd is
varied so as to correspond to the increase in the internal
resistance R associated with the deterioration of the battery 14 by
multiplying the internal resistance R by an inverse of the
deterioration correction coefficient .alpha. so that the
deterioration correction coefficient .alpha. is reflected in the
lower limit map voltage value Vmd. Note that in equation (3), the
current value I indicates the discharging current.
Vmd=OCV-I.times.R/.alpha. (3)
[0068] Next, in step S15, it is determined if the terminal voltage
Vb of the battery 14 is smaller than the lower limit map voltage
Vmd.
[0069] If the result of determination is "YES", then the process
proceeds to step S16 whereas the result of determination is "NO",
then the operation described in step S02 and thereafter will be
carried out.
[0070] In step S16, a forcible loading process is carried out for a
predetermined period of time (for instance, one second). That is,
in a hybrid vehicle, for instance, the output assistance level of
the engine 12 is decreased to zero, and the no-load state of the
battery 14 is forcibly created.
[0071] Next, in step S17, the terminal voltage OCV of the battery
14 in the no-load state is measured.
[0072] In step S18, based on the detected terminal voltage OCV in
the no-load state, for instance, the remaining charge SOC.sub.OCV
in the no-load state is calculated by searching the map which is
prepared based on the voltage characteristic of the battery 14 in
the no-load state (i.e., the battery 14 has no deterioration (e.g.,
at its initial state thereof)) and shows the relationship between
the terminal voltage OCV and the remaining charge SOC.sub.OCV.
[0073] In step S19, it is determined if the absolute value of the
difference between the detected remaining charge SOC and the
remaining charge SOC.sub.OCV in the no-load state is greater than a
predetermined value (for instance, 5%).
[0074] If the determination result is "YES", then the process
proceeds to step S11. On the other hand, if the determination
result is "NO", then the operation described in step S02 and
thereafter will be performed.
[0075] That is, for instance, as shown in FIGS. 3A through 3C, if
the current accumulation remaining charge SOC (i.e., SOC.sub.I
shown in FIG. 3C as a solid line) is calculated by the current
accumulation method for the battery 14 in which the charging state
has been maintained since its initial state and the internal
resistance R of the battery 14 is increased due to deterioration,
the upper limit map voltage value Vmu in the upper limit remaining
charge map which is set for the predetermined upper limit remaining
charge SOC.sub.MAP is decreased in accordance with the
equation:
Vmu=OCV-I.times.R
[0076] and the terminal voltage Vb of the battery 14 detected by
the voltage detector 28 reaches the upper limit map voltage value
Vmu at time t before the actual remaining charge SOC reaches the
predetermined upper limit remaining charge SOC.sub.MAP.
[0077] Accordingly, if the current accumulation remaining charge
SOC.sub.I is calibrated by using the upper limit remaining charge
SOC.sub.MAP in this state, the resulting calibrated current
accumulation remaining charge SOC.sub.I would be different from the
actual remaining charge SOC.
[0078] Thus, the no-load state of the battery 14 is created by, for
instance, forcibly stopping the regenerative operation at time t.
Then, after a predetermined time .DELTA.t (for instance, one
second) which is required for the stabilization of the no-load
state of the battery 14, the terminal voltage OCV of the battery 14
in the no-load state is measured to calculate the remaining charge
SOC.sub.OCV with respect to the terminal voltage OCV.
[0079] Since the SOC.sub.OCV is almost equal to the value of the
battery 14 having no deterioration and in the no-load state (e.g.,
in its initial state) regardless of the increase in the internal
resistance R associated with the deterioration of the battery 14,
the remaining charge SOC of the battery 14 may be detected with
high accuracy by calibrating the current accumulation remaining
charge SOC.sub.I using the remaining charge SOC.sub.OCV in the
no-load state.
[0080] Also, by correcting the upper limit remaining charge map
based on the remaining charge SOC.sub.OCV in the no-load state, the
current accumulation remaining charge SOC.sub.I may be calibrated
with high accuracy by the upper limit remaining charge
SOC.sub.MAP.
[0081] When the upper limit remaining charge map is corrected, the
upper limit map voltage value Vmu is increased by reflecting the
deterioration correction coefficient .alpha., which is the ratio of
the remaining charge SOC.sub.OCV in the no-load state to the upper
limit remaining charge SOC.sub.MAP as mentioned above, to the
internal resistance R so that the actual remaining charge SOC
reaches the predetermined upper limit remaining charge SOC.sub.MAP
at the same time that the detected terminal voltage Vb of the
battery 14 reaches the upper limit map voltage value Vmu at time
t.
[0082] As mentioned above, according to the remaining charge
detection device 10 of an embodiment of the present invention, the
remaining charge SOC may be detected, with high accuracy, by
correcting the current accumulation remaining charge SOC.sub.I
based on the remaining charge SOC.sub.OCV of the battery 14 in the
no-load state even if the difference between the current
accumulation remaining charge SOC.sub.I and the actual remaining
charge SOC of the battery 14 is increased by, for instance, an
increase in the internal resistance R of the battery 14 due to, for
example, a low temperature or the deterioration of the battery, a
transient state of the battery 14 in which current drifting is
frequently generated, or a high level output period in which the
amount of discharging current is increased.
[0083] Also, the current accumulation remaining charge SOC.sub.I
may be calibrated with high accuracy using the upper and lower
limit remaining charges SOC.sub.MAP by correcting the voltage value
V for the predetermined remaining charge correction map (for
instance, the upper limit map voltage Vmu and the lower limit map
voltage Vmd) which is used for correcting the current accumulation
remaining charge SOC.sub.I, such as the upper limit remaining
charge map and the lower limit remaining charge map, based on the
remaining charge SOC.sub.OCV for the battery 14 in the no-load
state.
[0084] Moreover, for the case where the remaining charge SOC of the
battery 14 is expressed as a percentage (%) with respect to the
standard charge SOCf due to a convenience for controlling, for
instance, the motor 11 and the engine 12, it becomes possible to
appropriately control the motor 11 and the engine 12 by using the
remaining charge SOC of high accuracy even if the battery 14 has
deteriorated because the standard charge SOCf is corrected based on
the remaining charge SOC.sub.OCV of the battery 14 in the no-load
state.
[0085] Note that although the value which is obtained by dividing
the remaining charge SOC.sub.OCV in the no-load state by the upper
limit or the lower limit remaining charge SOC.sub.MAP is used as
the deterioration correction coefficient .alpha. in the
above-mentioned embodiment of the present invention, it is not
limited as such and it is possible to correct, for instance, the
voltage value V and the remaining charge with respect to the
predetermined remaining charge correction map and the standard
remaining charge SOCf by using another coefficient which may be
converted into the deterioration correction coefficient
.alpha..
[0086] For example, although the upper limit map voltage Vmu and
the lower limit map voltage Vmd are corrected by multiplying the
inverse of the deterioration correction coefficient .alpha. by the
internal resistance R in the above-mentioned embodiment, it is
possible to correct the voltage value, for instance, by using the
correction coefficient .alpha.1 shown in the equation (4) below,
and setting the value obtained by multiplying the correction
coefficient .alpha.1 by the upper limit map voltage Vmu and the
lower limit map voltage Vmd, respectively, as a new upper limit map
voltage Vmu and a lower limit map voltage Vmd: 1 1 = ( SOCocv -
SOCmap SOCmap ) + 1.0 ( 4 )
[0087] Having thus described an exemplary embodiment of the
invention, it will be apparent that various alterations,
modifications, and improvements will readily occur to those skilled
in the art. Such alterations, modifications, and improvements,
though not expressly described above, are nonetheless intended and
implied to be within the spirit and scope of the invention.
Accordingly, the foregoing discussion is intended to be
illustrative only; the invention is limited and defined only by the
following claims and equivalents thereto.
* * * * *