U.S. patent application number 11/260158 was filed with the patent office on 2006-05-11 for dual type vehicle power-supply apparatus.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Shinya Goto, Tetsuya Kobayashi.
Application Number | 20060097576 11/260158 |
Document ID | / |
Family ID | 36315602 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060097576 |
Kind Code |
A1 |
Kobayashi; Tetsuya ; et
al. |
May 11, 2006 |
Dual type vehicle power-supply apparatus
Abstract
The dual type vehicle power-supply apparatus includes a
bidirectional power transmission unit capable of performing
bidirectional electric power transmission between a high voltage
source of a high power-supply voltage supply system and a low
voltage source of a low power-supply voltage supply system, and a
power transmission controller controlling the bidirectional power
transmission unit to perform the bidirectional electric power
transmission. The power transmission controller has a function of
detecting a surplus amount of electric power in the low
power-supply voltage supply system, a function of detecting a
shortage amount of electric power in the high power-supply voltage
supply system, and a function of commanding the bidirectional power
transmission unit to transmit electric power from the low voltage
source to the high voltage source by an mount equal to the detected
shortage amount when the detected surplus amount is larger than the
detected shortage amount.
Inventors: |
Kobayashi; Tetsuya;
(Anjo-shi, JP) ; Goto; Shinya; (Gifu-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
36315602 |
Appl. No.: |
11/260158 |
Filed: |
October 28, 2005 |
Current U.S.
Class: |
307/9.1 |
Current CPC
Class: |
B60L 2200/26 20130101;
B60L 58/20 20190201; Y02T 10/70 20130101; B60L 2210/10 20130101;
Y02T 10/92 20130101; Y02T 10/72 20130101 |
Class at
Publication: |
307/009.1 |
International
Class: |
B60L 1/00 20060101
B60L001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2004 |
JP |
2004-325003 |
Claims
1. A dual type vehicle power-supply apparatus comprising: a high
power-supply voltage supply system having a high voltage source
supplying a high power-supply voltage to a high voltage electrical
load; a low power-supply voltage supply system having a low voltage
source supplying a low power-supply voltage lower than said high
power-supply voltage to a low voltage electrical load; a
bidirectional power transmission unit capable of performing
bidirectional electric power transmission between said high voltage
source and said low voltage source; and a power transmission
controller controlling said bidirectional power transmission unit
to perform said bidirectional electric power transmission, wherein,
said power transmission controller includes: a first function of
detecting a surplus amount of electric power in said low
power-supply voltage supply system; a second function of detecting
a shortage amount of electric power in said high power-supply
voltage supply system; and a third function of commanding said
bidirectional power transmission unit to transmit electric power
from said low voltage source to said high voltage source by an
amount equal to said detected shortage amount when said detected
surplus amount is larger than said detected shortage amount.
2. The dual type vehicle power-supply apparatus according to claim
1, wherein said first function is configured to detect said surplus
amount on the basis of an electric power supply capacity of said
low voltage source of said low power-supply voltage supply system,
and an electric power amount which said low voltage electrical load
requires for a certain time period after electric power
transmission from said high voltage source to said low voltage
source by said bidirectional power transmission unit is
stopped.
3. The dual type vehicle power-supply apparatus according to claim
1, wherein said second function is configured to detect said
shortage amount on the basis of an electric power supply capacity
of said high voltage source of said high power-supply voltage
supply system, and an amount of an impending electric power demand
by said high voltage electrical load.
4. The dual type vehicle power-supply apparatus according to claim
3, wherein said high voltage source includes a main battery charged
by a generator driven by a vehicle engine, and said low voltage
source includes an auxiliary battery charged by said bidirectional
power transmission unit.
5. The dual type vehicle power-supply apparatus according to claim
4, wherein said power transmission controller includes a fourth
function of detecting a degree of degradation of said auxiliary
battery, and a fifth function of increasing a charging level of
said main battery if said degree of degradation of said auxiliary
battery detected by said fourth function is lower than a
predetermined degree, and increasing a charging level of said
auxiliary battery if said degree of degradation of said auxiliary
battery detected by said fourth function is not lower than said
predetermined degree, to thereby make said first function larger
than said shortage amount detected by said second function.
6. The dual type vehicle power-supply apparatus according to claim
4, wherein said second function is configured to determine an
electric power amount needed for starting said vehicle engine as
said amount of said impending electric power demand by said high
voltage electrical load.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to Japanese Patent Application
No. 2004-325003 filed on Nov. 9, 2004, the contents of which are
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a dual type vehicle
power-supply apparatus including a high power-supply voltage supply
system and a low power-supply voltage supply system.
[0004] 2. Description of Related Art
[0005] A dual type vehicle power-supply apparatus including two
batteries providing different power supply voltages is used in a
hybrid vehicle, for example. The high power-supply voltage supply
system of such a dual type vehicle power-supply apparatus is
intended to supply electric power to large electrical loads which
are turned on and off at frequent intervals. By supplying electric
power to such large electrical loads in high voltage, advantages of
reduction of size and weight of a power feeding system and
electrical loads, reduction of power transmission losses, and
increase of the cycle life of the power supply apparatus can be
obtained. The low power-supply voltage supply system is intended to
supply electric power to electrical loads which require relatively
small power in low voltage, such as electronic devices. Generally,
a lead-acid vehicle battery, which is low in price and easy to
replace, is used for the low power-supply voltage supply
system.
[0006] It is common that the dual type vehicle power-supply
apparatus is configured to generate a high voltage for its high
power-supply voltage supply system, and produces a low voltage for
its low power-supply voltage supply system by stepping down the
generated high voltage by use of a DC-DC converter, for
example.
[0007] In a hybrid vehicle, the high power-supply voltage supply
system must supply a large amount of electric power for starting a
vehicle engine very often. Accordingly, there is known a technique
for transmitting electric power back to the high power-supply
voltage supply system from the low voltage power-supply supply
system to thereby increase the feeding capacity of the high
power-supply voltage supply system before starting the engine, as
disclosed in Japanese Patent Application Laid-open No. 2002-176704
filed by the same inventors of the present application. Such a
technique makes it possible to downsize the high power-supply
voltage supply system.
[0008] However, although the backward power transmission technique
described above makes it possible to use a high power-supply
voltage supply system having a smaller feeding capacity (smaller
discharging capacity), it invites a problem that the lead-acid
battery of the low power-supply voltage supply system, which is low
in price and has a relatively short cycle life, reaches the end of
its useful life too soon. In addition, the backward power
transmission technique has another problem in that the fuel
consumption of a vehicle is lowered by the power transmission loss
produced during the backward power transmission.
SUMMARY OF THE INVENTION
[0009] The invention provides a dual type vehicle power-supply
apparatus including:
[0010] a high power-supply voltage supply system having a high
voltage source supplying a high power-supply voltage to a high
voltage electrical load;
[0011] a low power-supply voltage supply system having a low
voltage source supplying a low power-supply voltage lower than the
high power-supply voltage to a low voltage electrical load;
[0012] a bidirectional power transmission unit capable of
performing bidirectional electric power transmission between the
high voltage source and the low voltage source; and
[0013] a power transmission controller controlling the
bidirectional power transmission unit to perform the bidirectional
electric power transmission,
[0014] wherein,
[0015] the power transmission controller includes:
[0016] a first function of detecting a surplus amount of electric
power in the low power-supply voltage supply system;
[0017] a second function of detecting a shortage amount of electric
power in the high power-supply voltage supply system; and
[0018] a third function of commanding the bidirectional power
transmission unit to transmit electric power from the low voltage
source to the high voltage source by an amount equal to the
detected shortage amount when the detected surplus amount is larger
than the detected shortage amount.
[0019] With the dual type vehicle power-supply apparatus of the
invention configured to transmit electric power only by a required
minimum amount when there is, or there is expected a power supply
shortage in the high power-supply voltage supply system, the
degradation of the auxiliary battery of the low power-supply system
can be suppressed, and accordingly the electric power transmission
loss caused by performing the backward stepup power transmission
can be reduced to thereby improve the fuel consumption of the
vehicle, because it is possible to avoid the backward stepup power
transmission from being performed uselessly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In the accompanying drawings:
[0021] FIG. 1 is a diagram showing a configuration of a dual type
vehicle power-supply apparatus according to an embodiment of the
invention;
[0022] FIG. 2 is a flowchart showing the operation of a backward
stepup power transmission routine performed by the dual type
vehicle power-supply apparatus;
[0023] FIG. 3 is a flowchart showing the operation of a main
battery state checking subroutine included in the backward stepup
power transmission routine;
[0024] FIG. 4 is a flowchart showing the operation of an auxiliary
battery state checking subroutine included in the backward stepup
power transmission routine; and
[0025] FIG. 5 is a flowchart showing the operation of an engine
restart preparing subroutine included in the backward stepup power
transmission routine.
PREFERRED EMBODIMENTS OF THE INVENTION
[0026] FIG. 1 is a diagram showing a configuration of a dual type
vehicle-power supply apparatus according to an embodiment of the
invention.
[0027] The dual type vehicle power-supply apparatus includes a main
battery 1 having a rated output of about 300V, a bidirectional
power transmission unit 2 of the input/output insulation type, an
auxiliary battery 3 having a rated output of about 14V, and a
battery monitor 5 for monitoring the state of the main battery 1.
Reference numeral 4 denotes low voltage electrical loads, and 6
denotes a vehicle ECU (Engine Control Unit).
[0028] The main battery 1 constitutes a high power-supply voltage
supply system together with an engine starter including an
engine-driven/engine-starting generator/motor (not shown) and a
vehicle-driving motor/generator (not shown). The high power-supply
voltage supply system is connected to high voltage electrical loads
(not shown) consuming relatively large amounts of electrical
power.
[0029] The auxiliary battery 3, which is a conventional lead-acid
vehicle battery, constitutes a low power-supply voltage supply
system together with the low voltage electrical loads 4.
[0030] The bidirectional power transmission unit 2, which is
capable of performing two-way electrical power transmission between
the high power-supply voltage supply system and the low
power-supply voltage supply system, includes a bidirectional DC-DC
converter 7, a voltage detector 8a detecting an input voltage of
the DC-DC converter 7 (the voltage supplied from the main battery
1), a voltage detector 8b detecting an output voltage of the DC-DC
converter 7 (the voltage supplied to the auxiliary battery 3), an
output voltage command receiver 8c receiving an output voltage
command sent from the ECU 6, a stepup/stepdown command receiver 8d
receiving a stepup/stepdown command sent from the ECU 6, and a
controller 8e for controlling the entire operation of the
bidirectional power transmission unit 2.
[0031] The battery monitor 5 has, in addition to a conventional
function of measuring the voltage, load current and temperature of
the main battery 1 and informing the ECU 6 of the measured results,
a battery management function of detecting overcharging and
overdischarging of the main battery 1 for each of the battery
modules of the main battery 1 and informing the ECU 6 of the
detection results. The battery monitor 5 is constituted by a
current detector 5a detecting a load current of the main battery 1,
a voltage detector 5b detecting the terminal voltage of the main
battery 1, a temperature detector 5c detecting the temperature of
the main battery 1, and a microcomputer 5d controlling the entire
operation of the battery monitor 5.
[0032] The ECU 6, which is a microcomputer-based controller, has,
in addition to a conventional function of detecting the state of
the vehicle and controlling the operation of the vehicle in
accordance with the detected vehicle state, a function of
controlling the power transmission operation of the bidirectional
DC-DC converter 7 through the controller 8e on the basis of the
state of the main battery 1 detected by the battery monitor 5 and
the state of the low power-supply voltage supply system which the
ECU 6 itself detects. The ECU 6 includes a current detector 6a
detecting a load current of the auxiliary battery 3, a voltage
detector 6b detecting the terminal voltage of the auxiliary battery
3, a temperature detector 6c detecting the temperature of the
auxiliary battery 3, and a microcomputer 6d controlling the entire
operation of the ECU 6. The microcomputer 6d of the ECU 6
calculates a target terminal voltage of the auxiliary battery 3 on
the basis of the state of the auxiliary battery 1 (the actual
terminal voltage, load current, and temperature of the auxiliary
battery 3) and the state of the main battery 3 (the terminal
voltage, load current, and temperature of the main battery 3), and
sends the calculated target terminal voltage to the bidirectional
power transmission unit 2 as the output voltage command.
[0033] The controller 8e controls the bidirectional DC-DC converter
7 to perform a forward stepdown power transmission such that the
terminal voltage of the auxiliary battery 3 becomes equal to the
target terminal voltage in response to the output voltage command.
Since the configuration of the bidirectional DC-DC converter 7 and
the forward stepdown power transmission operation thereof are well
known, no further explanation is made here.
[0034] Next, explanation is made about the operation of the dual
type vehicle power-supply apparatus of this embodiment when it
performs the backward stepup power transmission. The backward
stepup power transmission routine is performed before restarting
the engine after the vehicle is idle-stopped. In the case of a
hybrid vehicle, preferably, the backward stepup power transmission
routine is performed periodically after the ignition key is turned
on.
[0035] As shown in FIG. 2, when the backward stepup power
transmission routine is initiated, the main battery 1 is checked by
a main battery checking subroutine SR100. Subsequently, the
auxiliary battery 3 is checked by an auxiliary battery checking
subroutine SR200. Finally, preparation for the engine restart in
terms of electric power supply is made by an engine restart
preparing subroutine SR300.
[0036] FIG. 3 is a flowchart showing the operation of the main
battery checking subroutine SR100. As shown in this figure, when
the main battery checking subroutine SR100 is initiated, the state
of the main battery 1 (the terminal voltage, load current, and
temperature of the main battery 1) are read at step S102.
Subsequently, the SOC (State Of Charge) of the main battery 1 is
calculated at step S104 as a measure representing a suppliable
electric power amount of the main battery 1 on the basis of the
state of the main battery 1. Alternatively the SOC may be
calculated by integrating the load current of the main battery 1.
Next, an amount of an impending electric power demand by the high
voltage electrical loads is calculated at step S106. Finally,
before returning to the main routine (the backward stepup power
transmission routine), a prospective shortage amount of electric
power in the high power-supply voltage supply system is calculated
at step S108 by subtracting the amount of the impending electric
power demand from the SOC (suppliable electric power amount) of the
main battery 1.
[0037] In this embodiment, the SOC of the main battery 1 means an
amount of practically dischargeable electric energy stored in the
main battery 1 and not the absolute capacity of the main battery 1.
And the amount of the impending electrical power demand means an
electric power amount needed for restarting the engine. Since the
electric power amount needed for restarting the engine depends on
the temperature of the engine, it is desirable to provide a map
containing a relationship between the engine temperature and the
required electric power amount.
[0038] FIG. 4 is a flowchart showing the operation of the auxiliary
battery checking subroutine SR200. As shown in this figure, when
the auxiliary battery checking subroutine SR200 is initiated, the
state of the auxiliary battery 3 (the terminal voltage, load
current and temperature of the auxiliary battery 3) is read at step
S202. Subsequently, the SOC of the auxiliary battery 3 is
calculated at step S203 as a measure representing a suppliable
electric power amount of the auxiliary battery 3 on the basis of
the state of the auxiliary battery 3. After that, a surplus amount
of electric power is calculated at step S204 by subtracting, from
the calculated suppliable electric power amount of the auxiliary
battery 3, an amount of electric power which the low voltage
electrical loads 4 needs for a certain time period after the
forward stepdown power transmission from the high power-supply
voltage supply system to the low power-supply voltage supply system
is stopped, and multiplying the subtraction result by the power
transmission efficiency of the bidirectional DC-DC converter 7 when
it performs the backward stepup power transmission.
[0039] After that, a degree of degradation of the auxiliary battery
3 is checked at step S206. If it is determined at the subsequent
step S 208 that the checked degree of the degradation is such that
the amount of the actually dischargeable electric power of the
auxiliary battery 3 is substantially smaller than the calculated
suppliable electric power corresponding to the SOC of the auxiliary
battery 3, a degradation flag is set to 1 at step S212, and if not,
the degradation flag is reset to 0 at step S210 before returning to
the main routine.
[0040] The degree of degradation of the auxiliary battery 3 can be
detected, for example, by measuring the time elapsed until the
terminal voltage of the auxiliary battery 3 which is supplying
electric power to the low voltage electrical loads 4 falls to a
certain value after the forward stepdown power transmission is
stopped.
[0041] FIG. 5 is a flowchart showing the operation of the engine
restart preparing subroutine SR300. As shown in this figure, when
the engine restart preparing subroutine SR300 is initiated, it is
checked at step S302 whether or not the surplus amount of electric
power in the low power-supply voltage supply system obtained
through the auxiliary battery checking subroutine SR200 is larger
than the prospective shortage amount of electric power in the high
power-supply voltage supply system obtained through the main
battery checking subroutine SR100. If the check result at step S302
is negative, it is checked whether the degradation flag is in the
set state or in the reset state. If it is found that the
degradation flag is in the set state, the main battery 1 is charged
at step S306 to such a level as to remove the prospective shortage
amount of electric power. If it is found that the degradation flag
is in the reset state, the auxiliary battery 3 is charged at step
S308 to such a level as to remove the prospective shortage amount
of electric power by performing the forward stepdown power
transmission. However, if the terminal voltage of the auxiliary
battery 3 exceeds a certain allowable limit while it is charged,
the forward stepdown power transmission is stopped halfway, and the
main battery 1 is charged to make up for the rest. After the main
battery 1 or auxiliary battery 3 is charged, it is checked again at
step S307 whether or nor the surplus amount of electric power is
larger than the prospective shortage amount of electric power.
[0042] If the check result at step S307 is affirmative, it is
checked whether or not the engine idle stop operation is on its way
at step S310. If the check result at step S310 is affirmative,
before returning to the main routine, the backward stepup power
transmission is carried out for transmitting electric power from
the low power-supply voltage supply system to the high power-supply
voltage supply system by an amount equal to the calculated
prospective shortage amount of electric power plus a certain
margin. This margin is determined to cover the charging and
discharging losses of the main battery 1 and electrical power
transmission losses. The amount of the electric power being
transmitted through the backward stepup power transmission can be
calculated on the basis of the output current and output voltage of
the DC-DC converter 7, or the load current and the terminal voltage
of the main battery 1 or the auxiliary 3.
[0043] On the other hand, if the check result at step S307 is
negative, the idle stop operation is prohibited from being
performed at step S309, and after that, return to the main routine
is made.
[0044] The above engine restart preparing subroutine SR300 may be
added with a step at which, if it is determined at step S307 that
the surplus amount of electric power in the low power-supply
voltage supply system is not larger than the prospective shortage
amount of electric power in the high power-supply voltage supply
system, the prospective shortage amount of electric power is
temporarily reduced, or the surplus amount of electric power is
temporarily increased. The temporal reduction of the prospective
shortage amount of electric power can be made by temporarily
interrupting supply of electric power to high voltage electrical
loads not essential for the engine restart operation. Likewise, the
temporal increase of the surplus amount of electric power can be
made by temporarily interrupting supply of electric power to low
voltage electrical loads not essential for the engine restart
operation such as head lights.
[0045] As explained above, the dual type vehicle power-supply
apparatus according to the embodiment of the invention is
configured to transmit electric power only by a required minimum
amount when there is, or there is expected a power supply shortage
in the high voltage supply stem. Accordingly, with this dual type
vehicle power-supply apparatus, the degradation of the auxiliary
battery can be suppressed, and accordingly the electric power
transmission loss caused by performing the backward stepup power
transmission can be reduced to thereby improve the fuel consumption
of the vehicle, because it is possible to avoid the backward stepup
power transmission from being performed uselessly.
[0046] It is needless to say that many modifications can be made in
the above described embodiment as described below.
[0047] The bidirectional DC-DC converter 7 may be replaced by a
pair of unidirectional DC-DC converters.
[0048] The battery monitor 5 may be so configured as to monitor the
state of the auxiliary battery 3 in place of the ECU 6.
[0049] The battery monitor 5 may be integrated with the
bidirectional power transmission unit 2.
[0050] Although the present embodiment is directed to a hybrid
vehicle having the idle-stop function, the present invention can be
applied to any normal vehicle having the idle-stop function.
[0051] The control of the backward stepup power transmission may be
performed by hardware process instead of software process by the
microcomputer.
[0052] The above explained preferred embodiments are exemplary of
the invention of the present application which is described solely
by the claims appended below. It should be understood that
modifications of the preferred embodiments may be made as would
occur to one of skill in the art.
* * * * *