U.S. patent application number 10/063794 was filed with the patent office on 2003-11-20 for high current pulse generator.
Invention is credited to Chung, Hsing-Chen, Shiue, Lih-Ren, Sun, Abel.
Application Number | 20030214269 10/063794 |
Document ID | / |
Family ID | 32395427 |
Filed Date | 2003-11-20 |
United States Patent
Application |
20030214269 |
Kind Code |
A1 |
Shiue, Lih-Ren ; et
al. |
November 20, 2003 |
HIGH CURRENT PULSE GENERATOR
Abstract
The present invention provides a high current pulse generator
for DC powered devices. The generator includes batteries as the
power source that charges supercapacitors as well as provides power
to the loads as required. During charging, the supercapacitors are
connected in parallel, but they are switched to series connection
by relays at the moment that the loads demand large currents. No
other controlling means except for relays in the circuit is
employed, so that the electric arrangement is simple, reliable, and
cost-effective. As the batteries are designed to deliver currents
at low discharge rates, the effective use-time of batteries is
prolonged. Furthermore, due to the high power densities of
supercapacitors, the readily available alkaline batteries can be
utilized in the power unit for electric power tools.
Inventors: |
Shiue, Lih-Ren; (Hsinchu,
TW) ; Sun, Abel; (Taipei, TW) ; Chung,
Hsing-Chen; (Hsinchu, TW) |
Correspondence
Address: |
JIANQ CHYUN INTELLECTUAL PROPERTY OFFICE
7 FLOOR-1, NO. 100
ROOSEVELT ROAD, SECTION 2
TAIPEI
100
TW
|
Family ID: |
32395427 |
Appl. No.: |
10/063794 |
Filed: |
May 14, 2002 |
Current U.S.
Class: |
320/166 |
Current CPC
Class: |
H02J 7/345 20130101;
H02J 7/0024 20130101; B25B 21/00 20130101 |
Class at
Publication: |
320/166 |
International
Class: |
H02J 007/00 |
Claims
1. A high current pulse generator as a power unit for DC powered
devices consisting: a DC voltage source; a plurality of capacitors
connected in parallel with each other and with said voltage source,
for storing large static charges provided by said voltage source
and for releasing said charges; a latch coupled to said capacitors,
for initiating storing charges of said capacitors; a power output
sensor coupled to said voltage source, for monitoring a power
output of said voltage source; a switching element for switching
said capacitors into series connection for releasing said charges
to generate electric impulses of high current; and a trigger
coupled to said switching element for initiating switching said
capacitors.
2. The high current pulse generator in accordance with claim 1,
wherein said voltage source is a primary battery.
3. The high current pulse generator in accordance with claim 2,
wherein said primary battery is selected from the following group
consisting of an alkaline battery and a metal-air battery.
4. The high current pulse generator in accordance with claim 1,
wherein said voltage source is a secondary battery.
5. The high current pulse generator in accordance with claim 4,
wherein said secondary battery is selected from the following group
consisting of a nickel-metal hydride battery, a lithium ion
battery, a lithium polymer battery, a lead-acid battery, a
metal-air battery, and a nickel-cadmium battery.
6. The high current pulse generator in accordance with claim 1,
wherein said voltage source is a renewable energy produced by using
a resource selected from the following group consisting of
hydrogen, hydrocarbons alcohol, solar radiation, wind, and
hydraulic waves.
7. The high current pulse generator in accordance with claim 1,
wherein said capacitor is selected from the following group
consisting of a supercapacitor, an ultracapacitor, and an electric
double layer capacitor.
8. The high current pulse generator in accordance with claim 7,
wherein said capacitor has a working voltage of >/=2.5V, a
capacitance of >/=1 F, and ESR </=100 m .OMEGA..
9. The high current pulse generator in accordance with claim 1,
wherein said power output sensor is a solenoid.
10. The high current pulse generator in accordance with claim 1,
wherein said switching element is an electromagnetic relay.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a compact power module for
generating impulses of high current for driving electric motors to
create impulse torque in short duration, thereby energizing
hand-held tools, igniting combustion engines, or actuating
automatic systems. More specifically, the present invention relates
to a switching capacitor without moving parts wherein
supercapacitors, ultracapacitors, or electric double layer
capacitors are configured from parallel connection during charging
phase to series connection at the time of use by electromagnetic
switching elements to discharge for generating the desired
impulses.
[0003] 2. Description of Related Art
[0004] Impulse energy is very useful in numerous industries. For
example, it can be used for crushing stones (U.S. Pat. No.
6,058,029), for vaporizing metal (U.S. Pat. No. 5,359,279), for
removing pollutant particles (U.S. Pat. No. 4,162,417), and for
collecting blood sample (U.S. Pat. No. 5,839,446).
[0005] Many techniques can be used to generate impulse energy, for
example, seawater and membrane used in submarine torpedo launch
systems for producing a high velocity fluid flow in a very short
duration (U.S. Pat. Nos. 5,200,572 and 6,146,114). High energy
pulses can also be generated by using acoustic transducer (U.S.
Pat. No. 4,541,081), piezoelectric transducer (U.S. Pat. No.
6,204,592) and flywheel (U.S. Pa. No. 5,511,715). Nevertheless,
impulse energy is most commonly generated using electrical
circuitry as in U.S. Pat. Nos. 4,258,405; 4,994,160; 5,359,279;
5,729,562; 5,895,584; 6,058,029; 6,063,168 and 6,359,424. Though
capacitor is universally included in the prior art electric impulse
generators, various semiconductor switching devices, such as,
thyratron, thyristor, IGBT or SCR, as well as coil, transformer and
microcontroller of pulse width modulation (PWM) are employed for
switching the capacitor. Because of the chip count in the prior art
electric impulse generators is high, the resultant electrical
arrangements are thus bulky and costly. Moreover, thyratron has a
lifetime problem associated with cathode and anode erosion that can
reduce switching efficiency and voltage hold-off ability of the
semiconductor element.
[0006] Impulse force is also required for operating portable hand
held tools including stapler, nailer, tacker, drill, hammer,
pinner, breaker, nibbler, compactor, hedger, trimmer, and pruner,
etc. Taking nailer or stapler as an example, it is conventionally
pneumatically powered by compressed air (U.S. Pat. No. 6,155,472)
or by pressurized fuel gas (U.S. Pat. No. 5,911,350) to charge the
spring to a compressed position for driving a nail into wood or
concrete surface. The aforementioned tools hence need a job site
compressor or a combustion chamber that impairs the mobility of the
tools. To bestow the portable tools the highest mobility, the tools
should have no string attached thereto or be cordless, and
preferably, the tools are powered by batteries. Similar to AC
powered tools, the DC powered tools utilize solenoid actuators in
driven applications as well. In U.S. Pat. No. 5,105,329 issued to
Goldner, which is included herein by reference, a solid-state
circuitry is provided for driving the armature of a battery
operated electric stapler. As batteries are the sole power source
for a DC stapler, the effective operating lifetime of batteries is
addressed by '329 by means of a complex circuit using a number of
electronic components. Nowadays, many commercial cordless power
tools rely at first on NiCd batteries and then switch to NiMH
batteries on environmental cause for driving the electric motors of
tools. However, batteries are limited to their power densities that
they are unable to deliver the required impulse torque for
heavy-duty jobs, or the effective use-time of batteries is reduced
due to overdraft of power. This invention provides a cost-effective
method using supercapacitors and electromagnetic relays to solve
the foregoing problems related to the electric impulses
generation.
SUMMARY OF INVENTION
[0007] The present invention utilizes supercapacitors as load
leveling for batteries in DC powered devices. Therefore, the number
of batteries required for powering the devices can be reduced, or
the effective operating time of batteries can be prolonged. When
alkaline batteries are employed in the power units of DC powered
devices, no wait time is required for charging batteries so that
the devices can perform immediately.
[0008] The present invention uses a minimum number of batteries,
but sufficient to charge the supercapacitors. When the loads demand
large currents, the supercapacitors will promptly supply the
required power, leaving batteries isolated or under a condition of
low discharge rate.
[0009] The present invention uses only electromagnetic relays as
the switching element to switch the supercapacitors from parallel
connection to series connection for delivering electric impulses.
The relays are small and inexpensive. Thereby, the impulse
generator consisting of supercapacitors and relays is compact and
cost-effective.
[0010] The present invention controls the capacitance and ESR
(equivalent series resistance) of the supercapacitors so that the
magnitude of impulse force (or impulse torque) provided by the
generator is tailor-made.
[0011] These and other features, objectives as well as advantages
in accordance with the present invention will become apparent from
the following detailed description, and from preferred embodiments
with the accompanying drawings.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0014] FIG. 1 is a schematic diagram illustrating that
supercapacitors are connected in parallel during charging and they
are switched to series connection for delivering electric impulses
upon pulling the trigger according to one preferred embodiment of
this invention;
[0015] FIG. 2 is a schematic diagram illustrating that
supercapacitors can discharge to assist battery to meet the power
demand at the request of load according to another one preferred
embodiment of this invention; and
[0016] FIG. 3 is a schematic diagram illustrating the voltage and
current pulses produced by the generator using alkaline batteries
as power source for operating an electric stapler according to
another one preferred embodiment of this invention.
DETAILED DESCRIPTION
[0017] Supercapacitors are energy-storage devices of
electrochemical cells that can store static charges up to thousands
of farads (F) via surface adsorption or surface redox (reduction
and oxidation). For adsorption, the charges stored are termed
double layer capacitance (DLC), while pseudocapacitance (PC) is
given for the charges stored by means of surface redox. Generally,
carbonaceous materials are observed to have DLC only, and metal
oxides are often seen to have both DLC and PC. Because of the
foregoing difference in storing charges, capacitors using carbons
as the electrode materials are named supercapacitors or electric
double layer capacitors, whereas capacitors using metal oxides as
the electrode materials are so called ultracapacitors.
Nevertheless, all of the aforementioned capacitors have high energy
densities compared to the conventional capacitors, and they all
possess high power densities compared to the batteries. Most
importantly, they are all suitable for making the high current
pulse generator as presented in the current invention.
[0018] Due to high energy densities, supercapacitors can be charged
by any magnitude of current as long as the rated voltages (10%
tolerance) of supercapacitors are not exceeded. To serve as an
electric impulse provider, the element employed should be capable
of storing energy and releasing energy in a very short duration at
request. In addition to supercapacitor, flywheel and inductor are
alternative candidates and they are frequently utilized for
delivering energy pulses. However, flywheel requires a driving
motor and other moving parts to operate, while inductor has
hysteresis and is seldom used alone. On the contrary,
supercapacitors receive and release energy in real-time response
without moving parts and delay. Moreover, supercapacitors can
literally perform charging and discharging for years without the
need of maintenance. Therefore, supercapacitors are better devices
than flywheels on delivering electric impulses.
[0019] FIG. 1 is a schematic diagram illustrating that
supercapacitors are connected in parallel during charging and they
are switched to series connection for delivering electric impulses
upon pulling the trigger. FIG. 1 is based on the first preferred
embodiment of the present invention on generating electric impulses
for driven applications such as stapler, nailer, tacker, hammer and
trimmer. The electric impulse generator 10 comprises battery B as a
voltage source, supercapacitors C1 and C2 as an energy storage
unit, and a 4-port (S1 to S4 as common contacts) electromagnetic
relay for switching the supercapacitors to discharge position. Each
port of the relay has a single-pole, double-throw (SPDT). Four sets
of 12 contacts of the relay are normally closed (S1a-S1, S2a-S2,
S3a-S3 and S4a-S4), while the other sets are normally open (S1-S1b,
S2-S2b, S3-S3b and S4-S4b). During charging phase, a DC current
will flow form battery B in power line 12 through contacts S1a and
S3a to charge supercapacitors C1 and C2, respectively. While the
supercapacitors are charged by the battery, motor M is grounded by
way of S4 and S4a. Since C1 and C2 are connected in parallel for
charging, the voltage of battery B is designed to be slightly
larger than that of supercapacitors C1 and C2, but much lower than
the voltage required for driving M. Henceforth, the dimension and
quantity of battery can be reduced. In order to save the energy of
the battery, there is a push-latching button (not shown in FIG. 1)
for initiating the charging of supercapacitors before using the
tools. While the tools are in storage, battery is isolated from the
supercapacitors and the motor. At the time of using the tools, the
latching button is pushed and trigger is pulled to switch the
electromagnetic relay from normally closed to normally open.
Consequently, the supercapacitors C1 and C2, as well as the motor M
are all connected in series. Immediately the supercapacitors
discharge to produce a high current to impart impulse torque to the
motor for driving the spring mechanism suddenly to a
spring-compressed position, in order to drive a staple from a
staple magazine. After firing a staple, the spring mechanism
automatically returns to the original position, ready for the next
operation. In FIG. 1, the diode D is to protect battery B from back
charging, while capacitor C3 is a conventional capacitor used for
absorbing voltage surge that may occur.
[0020] FIG. 2 is a schematic diagram illustrating that
supercapacitors can discharge to assist battery to meet the power
demand at the request of load according to another one preferred
embodiment of this invention. FIG. 2 is based on the second
embodiment of the present invention for generating high current
pulse to meet an increasing power demand of loads, such as, the
motor of power drills, the engine of motorcycles and automobiles,
as well as the actuator of automatic systems. Similar to FIG. 1,
the high current pulses generator 20 also comprises battery B as a
voltage source, supercapacitors C1 and C2 as an energy storage
unit, and a SPDT, 3-port electromagnetic relay for switching the
supercapacitors to discharge position. However, a solenoid S is
included in the generator of FIG. 2, and battery B supplies a DC
current that is within the normal discharge rates of battery for
charging the supercapacitors, as well as for driving the motor M
that requires low power for initial operation. During charging
phase, with the relay at normally closed (S1a-S1, S2a-S2 and
S3a-S3) state the supercapacitors C1 and C2 are connected in
parallel, and the DC current flowing through S is below the turn-on
threshold of the device. As the power demand of M increases, for
example, at the moment when the drill bit of a power drill is
penetrating a work piece or at the ignition of engines of vehicles,
the motors require a large impulse torque demanding more current
output from battery B. Along with an increasing DC current flowing
through S and exceeding the turn-on threshold of S, the switch of S
is closed and the electromagnetic relay is switched from normally
closed to normally open (S1-S1b, S2-S2b and S3-S3b). In a real-time
response, the supercapacitors C1 and C2 are connected in series and
discharge to generate a high current pulse to M in order to meet
the power demand. In the foregoing operation, the discharge of
battery B is kept at low rates. Thus, no abrupt voltage drop will
occur and the effective operating time of battery is prolonged.
EXAMPLE 1
[0021] Using 6 pieces of 1.5V alkaline batteries and 2 pieces of
7.5V.times.6F supercapacitors with ESR of 80-100 m .OMEGA., a high
current pulses generator as depicted by FIG. 1 is arranged for an
electrical stapler that originally relies on 12 pieces of
1.2V.times.1800 mAh NiCd batteries for operation. Soon after the
supercapacitors are charged, the generator can continuously drive 8
pieces of 1/2-inch staple into the surface of plywood. The
discharge curves of voltage and current pulses of the first 5 shot
are shown in FIG. 3. The average current required to operate the
stapler is 20A that is well above the current output of the
aforementioned alkaline batteries. When 6 pieces of the original
NiCd batteries or 6 pieces of NiMH batteries of the same
capacitance as the NiCd are used for the generator, the stapler is
highly energetic and shows no hesitation during operation.
EXAMPLE 2
[0022] Using 6 pieces of 3.6V.times.1600 mAh lithium ion batteries,
which are first grouped in 3 sets of double batteries connected
in-series, and then the 3 sets are connected in-parallel to form a
battery pack of 7.2V.times.4800 mAh, together with 2 pieces of 6.5V
.times.40F supercapacitors with ESR of 30 m .OMEGA., a high current
pulses generator as depicted by FIG. 2 is constructed. The
generator is capable of igniting a 2000-ml combustion engine of a
6-cylinder automobile. Also the generator weighed 1.4 lbs. is
measured to deliver an electric power of 720W (12V.times.60A) for 2
seconds per one full charge of supercapacitors. From the foregoing
two examples, the present invention demonstrated the following
features:
[0023] 1. Primary batteries such as alkaline batteries can be used
to operate electric power tools.
[0024] 2. With the assistance of supercapacitors, rechargeable
batteries of low power density such as NiMH and lithium ion can be
used to replace batteries of high power density such as lead-acid
and NiCd for performing heavy-duty jobs.
[0025] 3. Supercapacitors can enhance the power density of primary
and secondary batteries, as well as renewable energy including the
aforementioned batteries, fuel cells, solar cells, and metal-air
batteries. Furthermore, the power output of the generator
consisting of batteries and supercapacitors can be custom-made by
adjusting the capacitance of supercapacitors.
[0026] The present invention is viable as a power unit for
generating impulses of high current and is advantageous in
performance, convenience, compact, simplicity, reliability,
durability, and cost.
[0027] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *