U.S. patent application number 17/074698 was filed with the patent office on 2021-02-04 for engine kill switch and control assembly.
The applicant listed for this patent is Walbro LLC. Invention is credited to Martin N. Andersson, Cyrus M. Healy, Gerald J. LaMarr, JR., George M. Pattullo.
Application Number | 20210033036 17/074698 |
Document ID | / |
Family ID | 1000005152653 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210033036 |
Kind Code |
A1 |
Andersson; Martin N. ; et
al. |
February 4, 2021 |
ENGINE KILL SWITCH AND CONTROL ASSEMBLY
Abstract
A speed regulating circuit in communication with an ignition
circuit having a primary coil coupled to an ignition member to
cause an ignition event within an engine, the speed regulating
circuit being arranged to selectively prevent energy from the
primary coil from being discharged to the ignition member to
selectively prevent an ignition event. In at least some
implementations, the speed regulating circuit includes a
bidirectional or bilateral triode thyristor having an anode coupled
to the primary coil and an anode coupled to ground, and an input
gate that may be selectively actuated to route to ground energy
received at the triode thyristor from the primary coil to inhibit
transfer of energy from the primary coil to the ignition member.
The triode thyristor may be selectively actuated, for example, as a
function of engine speed, such as an engine speed above a threshold
speed.
Inventors: |
Andersson; Martin N.; (Caro,
MI) ; Healy; Cyrus M.; (Ubly, MI) ; LaMarr,
JR.; Gerald J.; (Bay City, MI) ; Pattullo; George
M.; (Caro, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Walbro LLC |
Tucson |
AZ |
US |
|
|
Family ID: |
1000005152653 |
Appl. No.: |
17/074698 |
Filed: |
October 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16072309 |
Jul 24, 2018 |
10844800 |
|
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PCT/US2017/014057 |
Jan 19, 2017 |
|
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17074698 |
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62364348 |
Jul 20, 2016 |
|
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62286691 |
Jan 25, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01H 2300/028 20130101;
F02P 1/086 20130101; F02D 41/26 20130101; F02D 41/04 20130101; A01D
34/76 20130101; F02P 5/1502 20130101; F02D 41/042 20130101; A01D
2034/907 20130101; F02P 9/002 20130101; H01H 23/16 20130101; F02N
11/08 20130101 |
International
Class: |
F02D 41/04 20060101
F02D041/04; F02D 41/26 20060101 F02D041/26; F02N 11/08 20060101
F02N011/08; F02P 1/08 20060101 F02P001/08; F02P 5/15 20060101
F02P005/15; F02P 9/00 20060101 F02P009/00; H01H 23/16 20060101
H01H023/16; A01D 34/76 20060101 A01D034/76 |
Claims
1. A speed regulating circuit in communication with an ignition
circuit having a primary coil coupled to an ignition member to
cause an ignition event within an engine, the speed regulating
circuit arranged to selectively prevent energy from the primary
coil from being discharged to the ignition member to selectively
prevent an ignition event, wherein the speed regulating circuit
includes a bidirectional or bilateral triode thyristor having an
anode coupled to the primary coil and an anode coupled to ground,
and an input gate that may be selectively actuated so that energy
received at the triode thyristor from the primary coil PRI is
routed to ground thereby inhibiting or preventing transfer of
energy from the primary coil to the ignition member.
2. The circuit of claim 1 wherein a microcontroller is communicated
with the input gate to control actuation of the triode
thyristor.
3. The circuit of claim 2 wherein the triode thyristor is actuated
when the engine speed is above a threshold speed.
4. The circuit of claim 1 which also includes a charge coil adapted
to have induced therein an alternating current, and a
microcontroller coupled to the charge coil and powered by a
negative portion of the alternating current, and wherein the
microcontroller provides a negative voltage signal to the input
gate of the triode thyristor.
5. The circuit of claim 2 which includes a charge coil adapted to
have induced therein an alternating current, and a power circuit,
the power circuit includes a capacitor, a diode and a transistor,
wherein an emitter of the transistor is coupled to both the
microcontroller and a capacitor, a collector of the transistor is
coupled between a resistor and the diode, and a base of the
transistor is coupled to the resistor, and wherein, negative
portions of the alternating current flow through the emitter and
the base and the capacitor is charged by the negative portions of
the alternating current, and wherein the capacitor is coupled to
the microcontroller to power the microcontroller.
6. The circuit of claim 5 wherein the microcontroller provides a
negative voltage signal to the input gate of the triode
thyristor.
7. The circuit of claim 6 wherein the triode thyristor is arranged
to pass through to ground both positive and negation portions of
the alternating current.
8. The circuit of claim 2 which includes a kill switch that is
coupled to the microcontroller and when the kill switch is actuated
the microcontroller actuates the triode thyristor to prevent at
least one ignition event.
9. The circuit of claim 8 wherein the kill switch is coupled to
ground and two resistors that are coupled to different inputs of
the microcontroller.
10. The circuit of claim 9 wherein the resistors are arranged as a
voltage divider.
11. The circuit of claim 1 which includes an alternating current
signal input and wherein the anode coupled to the primary coil is
coupled to the alternating current signal input and not directly to
the primary coil.
Description
REFERENCE TO CO-PENDING APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 16/072,309 filed on Jul. 24, 2018 which is a National
Phase Application of PCT/US2017/014057 filed on Jan. 19, 2017 and
claims the benefit of U.S. Provisional Application Nos. 62/364,348
filed on Jul. 20, 2016 and 62/286,691 filed on Jan. 25, 2016. The
entire contents of these priority applications are incorporated
herein by reference in their entireties.
TECHNICAL FIELD
[0002] The present disclosure relates generally to internal
combustion engines and more particularly to control systems for
such engines.
BACKGROUND
[0003] Small or utility internal combustion engines are used to
power a wide variety of various products such as electric
generators, air compressors, water pumps, power washers, lawn and
garden equipment such as garden tractors, tillers, chain saws, leaf
blowers, lawn mowers, lawn edgers, grass and weed trimmers, and the
like. Many of these engines are single cylinder two-stroke or
four-stroke and gasoline powered with a spark plug and an ignition
control module connected by two wires to the terminals of an engine
stop or kill switch. The kill switch is manually operable by an
operator to terminate supplying an electric current to the spark
plug and thus stopping operation of a running engine. Typically
these products do not have a separate battery for supplying an
electric current to the spark plug and instead utilize a magneto
system with magnets mounted on a flywheel of the engine to generate
electric power for a capacitive discharge ignition system which
often includes a microcontroller which typically varies and
controls ignition timing of the current at a high potential voltage
supplied to the spark plug of the operating engine. Typically these
engines are manually cranked for starting by an automatic recoil
rope starter.
SUMMARY
[0004] In at least some implementations, a kill switch assembly
includes an electric switch manually operated by an operator to
provide an engine kill or stop signal to the ignition control
system of an operating engine and circuitry for performing at least
one additional function such as receiving engine performance data
from its microcontroller to be stored in a kill switch
microcontroller, sending data to or receiving data from a computer,
sending temperature information to the engine microcontroller,
receiving a signal from the engine microcontroller to provide a
visually observable signal to the product operator, receiving a
signal from an external control circuitry for sending a signal to
the engine microcontroller to initiate a routine or process
programmed therein, and the like.
[0005] In at least some implementations, a kill switch assembly for
an internal combustion engine with an engine microcontroller
includes a housing, a first terminal carried by the housing and
configured for connection to a ground, a second terminal carried by
the housing and configured for connection to an engine
microcontroller, and an electric kill switch carried by the
housing, electrically connected to the first and second terminals,
and manually operable by an operator to change the state of the
electric switch to provide an engine stop signal to the engine
microcontroller. The assembly may also include an electronic
circuit carried by the housing, connected to the first and second
terminals, and communicating with the engine microcontroller. In at
least some implementations, the communication may occur wirelessly,
such as via bluetooth protocol.
[0006] A speed regulating circuit in communication with an ignition
circuit having a primary coil coupled to an ignition member to
cause an ignition event within an engine, the speed regulating
circuit being arranged to selectively prevent energy from the
primary coil from being discharged to the ignition member to
selectively prevent an ignition event. In at least some
implementations, the speed regulating circuit includes a
bidirectional or bilateral triode thyristor having an anode coupled
to the primary coil and an anode coupled to ground, and an input
gate that may be selectively actuated so that energy received at
the triode thyristor from the primary coil PRI is routed to ground
thereby inhibiting or preventing transfer of energy from the
primary coil to the ignition member. In at least some
implementations, the input gate may be coupled to a microcontroller
that selectively actuate the triode thyristor as a function of
engine speed, for example, an engine speed above a threshold
speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The following detailed description of certain embodiments
and best mode will be set forth with reference to the accompanying
drawings, in which:
[0008] FIG. 1 is a fragmentary perspective view of a grass and weed
trimmer with an engine kill switch assembly embodying the invention
and with some of the trimmer housing removed;
[0009] FIG. 2 is an enlarged fragmentary perspective view of a
portion of the trimmer housing carrying a kill switch assembly
embodying the invention;
[0010] FIG. 3 is a schematic diagram illustrating a capacitor
discharge ignition system and control module of an engine;
[0011] FIG. 4 is a schematic diagram of electronic circuitry of the
engine control module;
[0012] FIG. 5 is an enlarged sectional side view of the kill switch
assembly with its switch in its open position;
[0013] FIG. 6 is an enlarged sectional side view of the kill switch
assembly with its switch in its closed position;
[0014] FIG. 7 is an enlarged side view of a rocker button of the
kill switch assembly;
[0015] FIG. 8 is an enlarged bottom view of the rocker button taken
on line 8-8 of FIG. 7;
[0016] FIG. 9 is a sectional view taken on line 9-9 of FIG. 5;
[0017] FIG. 10 is a schematic diagram of circuitry with a
microcontroller of the kill switch assembly;
[0018] FIG. 11 is a schematic diagram of circuitry with a
modification of the circuitry of FIG. 10;
[0019] FIG. 12 is a schematic diagram of a modification of the
circuitry of FIG. 10 providing a data terminal of the kill switch
assembly;
[0020] FIG. 13 is a schematic diagram of circuitry adding a signal
light and a temperature sensor to the circuitry in FIG. 10 of the
kill switch assembly;
[0021] FIG. 14 is a schematic diagram of circuitry powered by a
battery of the kill switch assembly;
[0022] FIG. 15 is a schematic diagram of circuitry with a data
communication port or terminal of the kill-switch assembly;
[0023] FIG. 16 is a schematic diagram of a modification of the
circuitry of FIG. 15 so that a computer can communicate with the
microcontroller of the kill switch assembly when the engine is not
running;
[0024] FIG. 17 is a sectional side view of the kill switch assembly
illustrating a modification of its rocker button to receive a male
connector plug;
[0025] FIG. 18 is a schematic diagram with a signal switch function
of the kill switch assembly;
[0026] FIG. 19 is an enlarged sectional side view of the kill
switch assembly to include a signal switch which is shown in the
closed position;
[0027] FIG. 20 is an enlarged sectional side view of the kill
switch assembly of FIG. 19 with the signal switch releasably
retained in an open position by a fixture;
[0028] FIG. 21 is an enlarged sectional side view of the kill
switch assembly of FIG. 19 with the signal switch releasably
retained in an open position by a tool removably received in the
rocker button;
[0029] FIG. 22 is a schematic diagram of an alternative circuit
with a signal switch of the kill switch assembly;
[0030] FIG. 23 is a bottom view with a portion broken away of the
kill switch assembly of FIG. 22;
[0031] FIG. 24 is a schematic diagram of a circuit including a kill
switch and a wireless transmitter and/or receiver;
[0032] FIG. 25 is a schematic diagram of circuitry like that of
FIG. 24 powered by a battery of the kill switch assembly;
[0033] FIG. 26 is a schematic diagram of circuitry for limiting
engine speed; and
[0034] FIG. 27 is a schematic diagram of circuitry for limiting
engine speed and including a kill switch
DETAILED DESCRIPTION
[0035] FIGS. 1 and 2 illustrate a handheld power tool or product in
the form of a grass and weed string trimmer 20 powered by a small
or light duty internal combustion engine 22. Typically, this engine
is a single cylinder two-stroke or four-stroke gasoline powered
internal combustion engine. In this engine, a single piston is
slidably received for reciprocation in a cylinder and connected by
a tie rod to a crankshaft 24 attached to a flywheel 26. Typically,
this engine has a capacitive discharge ignition system (CDI) module
28 for supplying a high voltage ignition pulse to a spark plug 30
for igniting an air-fuel mixture in the engine cylinder combustion
chamber. This module 28 varies and controls the ignition timing
relative to the top dead center position of the piston in response
to changing engine operating conditions.
[0036] Typically, this engine does not have any battery supplying
an electric current to the spark plug or powering the control
module 28 which typically includes a microcontroller. Typically,
this engine is manually cranked for starting with an automatic
recoil rope starter.
[0037] The term "light-duty combustion engine" broadly includes all
types of non-automotive combustion engines including two and
four-stroke gasoline powered engines used in various products
including portable electric generators, air compressors, water
pumps, power washers, snow blowers, personal watercraft, boats,
snowmobiles, motorcycles, all terrain vehicles, lawn and garden
equipment such as garden tractors, tillers, chainsaws, edgers,
grass and weed trimmers, air blowers, leaf blowers, etc.
[0038] As shown in FIGS. 1 and 2, the engine has a carburetor 32
having a throttle valve 34, typically a rotary barrel or butterfly
valve, connected by a Bowden wire 36 to a manually operable
throttle lever 38 pivotally mounted 40 in a handle housing 42 of
the trimmer. The throttle lever has a manually engageable trigger
44 extending outwardly of the handle housing and an arm 46
extending generally radially relative to the pivot 40 and
preferably at about a right angle to the trigger 44. At its distal
end, this arm has a generally axially extending dog 48 releasably
engageable with a stop 50 on a safety release latch 52 pivotally
mounted adjacent its other end in the handle housing on a pivot
axis 54 preferably parallel to the pivot axis 40 of the throttle
lever 38. The safety latch 52 retains the throttle lever 38 in its
idle position (FIG. 3) until the safety latch is manually depressed
to disengage its stop 50 from the dog 48 to thereby permit manually
moving the trigger 44 and thus the throttle lever 38 from its idle
position toward and to its wide open throttle (WOT) position to
move the wire 56 of the flexible Bowden cable assembly 36 to move
the carburetor throttle valve 34 from its idle position toward and
to its wide open position. The safety latch 38 is yieldably biased
to its latched position by a leaf spring 58.
[0039] FIG. 3 schematically illustrates a magneto system 156, the
control module 28 and a kill switch assembly 60 of the trimmer 20.
The kill switch assembly 60 has a kill switch 64 (FIGS. 5-9) and
circuitry discussed in detail here after. This magneto system
includes a permanent magnet element 160 with pole shoes 162, 164
and a permanent magnet 166 mounted on the flywheel 26 such that
when rotating it induces a magnetic flux in a nearby stator
assembly 168 of the module 28 as the magnet element passes
thereby.
[0040] The stator assembly 168 may include a lamstack 170 having a
first leg 172 and a second leg 174 (separated from the rotating
flywheel by a relatively small and measured air gap which may be
about 0.3 mm), a charge coil winding 176, an ignition primary coil
winding 178 and a secondary coil winding 180 which may all be
wrapped around a single leg of the lamstack. The lamstack 170 may
be a generally U-shaped ferrous armature made from a stack of iron
plates and may be in a module housing located on the engine. The
ignition primary and secondary coil windings 178, 180 may provide a
step-up transformer and as is well known by those skilled in the
art, the primary winding 178 may have a comparatively few turns of
a relatively heavy gauge wire, while the secondary ignition coil
winding 180 may have many turns of a relatively fine wire. The
ratio of turns between the primary and secondary ignition windings
generates a high voltage potential in the secondary winding that is
used to fire the spark plug 30 of the engine 22 to provide an
electric arc or spark and consequently ignite an air-fuel mixture
in the engine combustion chamber.
[0041] As shown in FIG. 4, the power charge coil 176 and the
ignition primary and secondary coils 178, 180 are coupled to an
ignition and control circuit 182 of the control module 28. The term
"coupled" broadly encompasses all ways in which two or more
electrical components, devices, circuits, etc. can be in electrical
communication with one another; this includes, but is not limited
to, a direct electrical connection and a connection via an
intermediate component, device, circuit, etc. This circuit 182
includes an energy storage and ignition discharge capacitor 184, an
electronic ignition switch 186 preferably in the form of a
thyristor, such as a silicon controlled rectifier (SCR), and a
microcontroller 188. One end of the power charge coil 176 is
connected through a diode 190 to the ignition capacitor 184. A
resistor 192 may be coupled in parallel with the capacitor. The
other end of the coil is connected through a diode 194 to the
circuit ground 196. A majority of the energy induced in the power
charge winding 176 is supplied to the capacitor 184 which stores
this energy until the microcontroller 188 changes the switch 186 to
a conductive state to discharge the capacitor 184 through the
primary coil 178 of the transformer which induces in the secondary
coil 180 a high voltage potential which is applied to the spark
plug 30 to provide a combustion initiating arc or spark. More
specifically, when the ignition switch 186 is turned "on" (in this
case, becomes conductive), the switch 186 provides a discharge path
for the energy stored on ignition discharge capacitor 184. This
rapid discharge of the ignition capacitor 184 causes a surge in
current through the primary ignition coil 178, which in turn,
creates a fast-rising electromagnetic field in the primary ignition
coil. The fast-rising electromagnetic field induces a high voltage
ignition pulse in the secondary ignition coil 180. The high voltage
ignition pulse travels to spark plug 30 which, assuming it has the
requisite voltage, provide a combustion-initiating arc or spark.
Other sparking techniques, including flyback techniques, may be
used instead.
[0042] The microcontroller 188 may include a memory 198 which can
store a look-up table, algorithm and/or code to determine and vary
the engine ignition timing relative to top dead center of the
piston in the cylinder for various engine operating speeds and
conditions. In some applications, the microcontroller 188 may also
vary and control the fuel-to-air ratio of the air-and-fuel mixture
supplied to the cylinder of the operating engine in response to
various engine operating speeds and conditions. Various
microcontrollers or microprocessors may be used as is known to
those skilled in the art. Suitable commercially available
microcontrollers include Atmel ATtiny series and Microchip PIC 12
family. Examples of how microcontrollers can implement ignition
timing systems can be found in U.S. Pat. Nos. 7,546,846 and
7,448,358, the disclosures of which are incorporated herein by
reference. The memory 198 may be a reprogrammable or flash EEPROM
(electrically erasable, programmable read-only memory). In other
instances, memory 198 may be external of and coupled to the
microcontroller 188. The memory 198 should be construed broadly to
include other types of memory such as RAM (random access memory),
ROM (read-only memory), EPROM (erasable, programmable read-only
memory), or any other suitable non-transitory computer readable
medium.
[0043] As shown in FIG. 4, the microcontroller 188 includes eight
pins. Pin 8 of the microcontroller can be coupled to a voltage
source (Vcc) which supplies the microcontroller with power. To
power this microcontroller, the circuit 182 has a diode 200,
capacitors 202, 204, a zener diode 206, and resistors 208 and 210
electrically connected in the circuit to the power coil and to pin
8. In this example, pin 1 is a reset pin that is connected through
a diode 212 to pin 8. Pin 2 is coupled to the gate of ignition
switch 186 via resistor 214, which is wired in the circuit with a
zener diode 216, and transmits from the microcontroller 188 an
ignition signal which controls the state of the switch 186. When
the ignition signal on pin 2 is low, the ignition switch 186 is
nonconductive and capacitor 184 is allowed to charge. When the
ignition signal is high, the ignition switch 186 is conductive and
the ignition capacitor 184 discharges through primary ignition coil
178, thus causing a high-voltage ignition pulse to be induced in
secondary ignition coil 180 and applied to the spark plug 30. Thus,
the microcontroller can govern the discharge of capacitor 184 by
controlling the conductive state of the switch 186.
[0044] Pin 3 is a general purpose input or output program port
which is not used. Pin 4 is a ground which is connected to the
circuit ground.
[0045] Pin 6 is a signal input connected to the charge winding 176
via resistors 218 and 220, zener diode 222, and capacitor 224 to
receive an electronic signal representative of the position of an
engine piston in its combustion chamber usually relative to the top
dead center (TDC) position of the piston. This signal can be
referred to as a timing signal. The microcontroller 188 can use
this timing signal to determine engine speed (RPM), the timing of
an ignition pulse relative to the piston(s) TDC position (usually
from a look-up table), and whether or not and, if so, when to
activate an ignition pulse.
[0046] Pin 7 is an output signal pin which is connected to input
pin 5 through resistors 226 and 228. So that pin 5 is not affected
by noise and radio frequency interference (RFI) produced by the
spark plug 30, pin 5 is also connected through a capacitor 230 to
the circuit ground 196.
[0047] In use, the spade connector terminal 72 of the kill switch
64 is connected to the ground 196 of the circuit. The other
connector spade terminal 70 of the kill switch is connected to the
junction 232 between the first and second resistors 226 and 228.
Preferably the first resistor 226 has a resistance value which is
in the range of 2 to 20 kOhms, desirably 2 to 12 kOhms, and
preferably 2 to 4 kOhms. Desirably, the second resistor 228 has a
resistance value in the range of 2 to 2.5 kOhms and preferably 2.2
kOhms. Preferably, the capacitor 230 has a capacitance of about 1
nanofarad.
[0048] When the engine is operating, the microcontroller 188 is
powered up to receive a signal through pin 6 from which it
determines the engine speed or RPM and the position of the piston
normally relative to top dead center. Through pin 3, the
microcontroller controls the state of the SCR switch 186 to charge
the capacitor 184, and typically uses a look-up table stored in
memory 198 to determine ignition timing, and changes the state of
the ignition switch 186 to discharge the capacitor to produce a
spark or arc in the gap of the spark plug 30 to initiate combustion
of the fuel-to-air fuel mixture in the engine cylinder. When the
kill switch 64 is open (as shown in FIGS. 4 and 5), the
microcontroller 188 produces on pin 5 an alternating signal of zero
volts and 5 volts.
[0049] Whenever the kill switch 64 is closed, the input at pin 5 is
zero volts which the microcontroller interprets as a command to
shut down the engine and "turns on" and "holds on" the ignition
switch 186 to prevent further high potential voltage pulses being
supplied to the spark plug 30 and thus terminating ignition of the
fuel mixture in the cylinder until the engine stops or ceases
operation.
[0050] In accordance with a feature of this invention, a kill
switch assembly 60 has a circuit board 62 and an engine kill switch
64 both in the same housing 66. Preferably, housing 66 is mounted
in the same location 68 in the handle housing as a conventional
engine kill switch. This kill switch assembly 60 has two preferably
spade connector terminals 70, 72 one of which is connected to a
ground wire 74 and the other is connected to a an engine module
communication wire 76 for the purposes of the circuitry of the
assembly 60 communicating through these wires with the
microcontroller 188 of the engine module 28 and to send another
signal to kill or stop the running engine when the operator
manually actuates a rocker button 78 of the kill switch 64 to stop
operation of the engine. In prior art trimmers and the like, a
manually actuated conventional rocker switch only provides a signal
to kill or stop the operating engine typically by a control circuit
microcontroller discontinuing or stopping the application of the
high potential voltage to the spark plug so that it does not ignite
any air-fuel mixture in the engine cylinder. The kill switch
housing 66 is electrically non-conductive and insulative and may be
a plastic housing.
[0051] As shown in FIGS. 5 and 6, the switch assembly 60 has a pair
of spaced-apart electrically conductive posts 80, 82 fixed in a
bottom wall 86 of the switch housing and adjacent one end
projecting into a pocket 88 in this housing to provide a pair of
spaced-apart contacts 90, 92 and adjacent the other end projecting
exteriorly of the housing to provide the pair of spaced-apart
terminals 70, 72, such as spade terminals, each of which is
connected to a separate one of the wires 74, 76 such as through
push-on female spade electrical connectors 94, 96. The manually
movable rocker button 78 is pivotally mounted in the housing to
pivot or see-saw about its pivots 98. An electrically conductive
connector bar 100 is received in a slot 102 through the button and
has projecting tabs 104 slidably received in spaced-apart blind
slots 106 in the rocker button. The connector bar 100 can see-saw
about a pivot pin 108 slidably received in a blind bore 109 (FIG.
11) in the rocker button and yieldably biased by a spring 110 into
contact with the connector bar and toward the distal end of the
slots and the bottom of the rocker button. As shown in FIGS. 8 and
9, in assembly, a recess 112 in the rocker button is slidably
received over a guide rib 114 of the switch housing and yieldably
biased to an open position (shown in FIG. 5) in which the connector
bar does not engage at least one or both of the contacts 90, 92 and
thus the kill switch 64 is in an open condition. The kill switch is
biased to its open position by a spring 116 received in a blind
pocket 118 in the rocker button and bearing on a portion of the
guide rib 114. When the portion of the rocker button projecting
outwardly from the housing is manually depressed, the button pivots
clockwise from a first position (FIG. 5) to a second position (FIG.
6) which moves the connector bar 100 into engagement with both of
the contacts 90, 92 to close the switch for as long as the rocker
button is manually depressed and when released the spring 116
returns the rocker button to the first position in which the
connector bar is disengaged from at least one of the contacts to
open the switch as shown in FIG. 5.
[0052] As shown in FIG. 9 the kill switch assembly 60 has a circuit
board 130 carried by and preferably within the housing 66 which
contains electronic circuitry connected to the terminals 70 and 72.
The configuration of this circuitry may vary depending on the
function it performs. Suitable circuits for performing various
different functions are described hereinafter and as will be
apparent to one of ordinary skill in the art these circuits have
many of the same components many of which are arranged in the same
configuration in most of these circuits. In these various circuits
the same component has the same reference number and will be
described in detail only once and its disclosure will not be
repeated and is incorporated by reference in the disclosure and
description of the other circuits to avoid unnecessary
repetition.
[0053] FIG. 10 illustrates a circuit 300A which may receive current
and/or historical performance data via terminal 70 and wire 74 from
the engine microcontroller 188 and its memory 198. This circuit
300A has a microcontroller 302 with 8 pins and a memory 304 in
which data may be stored and from which data may be retrieved.
While the engine is running the microcontroller 302 is powered by
the engine module 28 through a diode 306 and resistor 308 connected
to pin 4 of the microcontroller 302 and terminal 70. A capacitor
310 and a zener diode 312 connected across the resistor 306 and to
the circuit ground 314 filter out the circuit noise and limit the
voltage applied to pin 4. Pin 7 is connected by a resistor 316 to
terminal 7 and terminal 70 to transmit data to and receive data
from the engine microcontroller 188 through wire 74. The kill
switch 64 is connected to terminal 70 and through the ground 314 to
terminal 72. The microcontroller ground pin 6 is connected to
ground 314 and through terminal 72 and wire 76 to the ground 196 of
the engine control circuit 182.
[0054] FIG. 11 illustrates a modified circuit 300B which is the
same as the circuit 300A except that the pin 8 of the
microcontroller is connected by a resistor 318 to terminal 70 to
thereby use pin 8 to transmit data from the microcontroller 302 and
its memory and to the engine microcontroller 188 and its memory and
to use pin 7 to receive data from it.
[0055] FIG. 12 illustrates a circuit 300C which is the same as the
circuit 300B except that pins 7 and 8 of the microcontroller 302
are also connected (respectively through resistors 316 and 318) to
a separate data port or terminal 320 for communicating with the
engine microcontroller 188 of the module 28. This port 320 can be
carried by the housing 60 and be accessible from the exterior of
the housing.
[0056] FIG. 13 illustrates a circuit 300D which is the same as the
circuit 300A with the addition of a light emitting diode 322
connected through a resistor 324 to pin 1 of the microcontroller
302 and a temperature sensor thermistor 326 connected to pin 5 of
the microcontroller. The microcontroller 302 can receive a signal
from the engine microcontroller 188 of the module 28 to provide the
operator with a visual indication of something occurring or that
has occurred in either the engine module 28 and/or the operation of
the engine. The thermistor 326 can provide to the engine
microcontroller 188 of the module 28 an indication of the ambient
temperature in which the engine is operating since in at least most
products the kill switch assembly 60 is sufficiently distal from
the engine that it is not significantly affected by the heat
produced by the operating engine and/or the engine exhaust. The
light emitting diode 322 and/or the thermistor 326 can be added to
any of the circuits of the kill switch assembly 60.
[0057] FIG. 14 illustrates a circuit 330 in which the
microcontroller 302 is powered by a battery 332 connected to pin 4
of the microcontroller. The remaining components of the circuitry
330 having the same reference number as those of the circuit 300A
and are connected in the same relationship to the microprocessor
302, terminals 70 and 72, and switch 64 as those described in
connection with circuit 300A. The battery 332 may be used to power
the microcontroller 302 in any of its circuits in lieu of the diode
306, and resistor 308 connected to pin 4, and the capacitor 310 and
zener diode 312 connected across the resistor 308.
[0058] FIG. 15 illustrates a circuit 300D which is the same as the
circuit 300A except that a data terminal 334 has been added which
is connected through resistors 336 and 338 to pins 2 and 3
respectively of the microcontroller 302 for the purpose of
transmitting data to or receiving data from the microcontroller 302
and its memory 304 and/or through the microcontroller 302
transmitting data or a signal to or receiving data or a signal from
the engine microcontroller 188 and its memory 198. The port or
terminal 334 can be carried by the housing 66 of the kill switch
assembly 60 and be accessible from the exposed exterior of the
housing.
[0059] FIG. 16 illustrates a circuit 300E which may be connected to
and powered by a personal computer so that data can be received
from the microcontroller 302 and its memory 304 and/or data can be
transmitted to the microcontroller 302 and its memory 304 to
reprogram them, when the engine is not running. For connecting the
computer this circuit has a port 342 with a connector or terminal
344 connected to the micrcontroller transmission pin 2, a terminal
346 connected to data receiving pin 3, a terminal 348 connected to
power pin 4, and a terminal 350 connected to the circuit ground
314.
[0060] FIG. 17 illustrates a modified rocker button 78' that allows
an electric connector plug 352 to be directly connected with the
terminal 70 through the connector bar 100. The connector plug has a
body 354 with a cylindrical shank or pin 356 slidably received in a
bore 360 through the rocker button 78'. The connector plug has an
electrically conductive tip 360 which bears on and engages the
conductor bar 100 and is connected to an electric wire 362 through
which signals can be sent and received via the conductor 100,
terminal 70 and wire 74 directly to engine microcontroller 188 of
the module 28. This connector plug 352 may be used to send a signal
from an external control circuit with an electric switch manually
operable by an operator to change its state to send a signal to the
engine microcontroller 188 to start and execute a process or
routine stored in the microcontroller 188 and its memory. An
example of one such routine is a process which tests the
air-to-fuel ratio of an air-fuel mixture supplied to an operating
engine and if need be changes the air-to-fuel ratio to improve
engine performance and/or to meet exhaust emission
requirements.
[0061] FIG. 18 illustrates a circuit 300F which is the same as
circuit 300B except that a signal switch 370 manually actuatable by
an operator has been added to cause the microcontroller 302 to send
a signal to the engine microcontroller 188 to initiate and execute
a process or routine stored in its memory 198. One terminal 312 of
the normally closed switch 370, is connected to pin 1 and through a
resistor 374 to pin 4 of the microcontroller. The other terminal
376 of the signal switch is connected through a resistor 378 to
ground 314, and thus, to terminal 72. When switch 370 is manually
opened by the operator it sends a signal to pin 1 which causes the
microcontroller 302 to send a start signal to the engine
microcontroller 188 to initiate and execute a process or routine
such as the air-to-fuel ratio test noted above. Of course it could
initiate other processes or routines.
[0062] FIGS. 19 and 20 illustrate one form of the signal switch 370
in the kill switch assembly 60 in which a conductor pin 379 is
carried by the housing 60 and underlying the connector bar 100
provides the contact 376 and the contact 90 and its terminal 70
also provide the signal switch contact 372. The signal switch 370
is closed when the rocker button 78 is in its normal position to
which is it is yieldably placed by a spring 116 as shown in FIG.
19. As shown in FIG. 20 when the rocker button 78 is moved to its
middle position it disengages the connector bar 100 from the pin
379 and thereby opens the signal switch 370. A special fixture or
tool 380 with a recess 386 can be disposed over the rocker button
with its stop surface 384 bearing on the face 386 of the housing 66
to reliably move the rocker button to its center position and
thereby open the switch 370.
[0063] FIG. 21 illustrates an alternate tool 388 for moving and
positioning the rocker button 78 in its middle position. Tool 388
has a cylindrical shaft 390 with a generally conical tip 392
slidably received in a bore 394 through the rocker button and a
generally right angle member 396 with a first leg 398 fixed to and
projecting radially outwardly from the shank and bearing on a
peripheral edge of the rocker button 78 and a second leg 400 with a
free end 402 providing a stop bearing on the outer face 386 of the
housing 66.
[0064] FIG. 22 illustrates an alternative circuit 410 in which the
signal switch 370 is manually operable by the operator to send a
start signal to the microcontroller 302 to cause it to send a start
or control signal to the engine microcontroller 188 to start and
execute a routine or process stored in it and its memory. The
contact 372 of signal switch 370 is connected to terminal 70 and
the contact 376 is connected through resistor 378 to ground 314.
Thus, as shown in FIG. 23 the resistor 23 is connected to terminal
72 and conductor pin 379 in the housing 66 of the kill switch
assembly 60.
[0065] The functions and features of the kill switch circuitry may
also be transmitted wirelessly, received wirelessly or both, as
shown in FIG. 24 which illustrates one example of a control circuit
450 having a wireless module 452. In the example shown the wireless
module 452 is a transceiver that utilizes the Bluetooth standard,
although any suitable wireless protocol or standard may be used.
The transceiver 452 has power 454, transmitter 456 and receiver 458
connections, respectively, to the microcontroller 460 and a ground
connection 462. The remainder of the circuit 450 may be as set
forth in and described with reference to the circuit 300A of FIG.
10, or otherwise arranged as desired and similar reference numerals
denote similar components for ease of description. Engine operating
data, control logic for the microcontroller 460 and other features
and functions that could be done via a wired connection may thus be
communicated wirelessly between the circuit 450 and a device
external to the tool, such as a computer, smartphone, tablet,
engine diagnostic tool, or the like. In addition, the wireless
transmission of a signal from the circuit 450 may permit additional
functions, such as providing a location of the tool including the
circuit to, for example, facilitate finding a lost or stolen
device. FIG. 25 illustrates a similar circuit 470 that includes a
battery 472 to power the circuit 470 and so does not need power
supply components 306, 308, 310 or 312, but otherwise may be the
same as the circuit of FIG. 24 and similar reference numbers have
been used to denote similar components for ease of description. The
battery 472 may permit communication with the wireless module 452
or microcontroller 460 even when the engine is not operating and
power is not supplied from the magneto-capacitive circuit as noted
herein.
[0066] Providing the wireless communication module near the kill
switch 64 or as part of the kill switch assembly may improve the
operation of the device, at least in applications wherein the kill
switch is located remotely from and not on or immediately adjacent
to the engine and/or flywheel which may create EMF interference
that makes detection of transmitted signals more difficult. For
example, in the application of a weed trimmer or lawn edger, the
kill switch may be provided on a handle that is spaced 6 inches or
more from the engine or flywheel. Locations closer to the engine
may also be used, but signal detection may be more difficult
because of interference associated with such locations.
[0067] A control circuit 500 of FIG. 26 may be used to limit engine
speed, such as by preventing delivery of a spark, or other ignition
initiating event from an ignition member, to prevent combustion for
one or more engine cycles. This may be done, for example, to
prevent an engine from exceeding a maximum speed, which may vary
depending upon the application, the use of the engine, ambient
temperature or any other desired factor. The circuit 500 may
include a speed regulating circuit 502 (for limiting the engine
speed), a power circuit 504 (for powering a microprocessor 510
while protecting the microprocessor from overvoltage scenarios), a
clock circuit 506 (for synchronizing the microprocessor 510 to the
engine speed), and a programming circuit 508 (for programming a
microcontroller 510--e.g., for programmable RPM rates and the
like).
[0068] The speed regulating circuit 502 is configured to
selectively prevent energy at the primary coil (PRI) from being
discharged which in turn would otherwise create a spark at the
ignition member (e.g. a spark plug). In the current embodiment, the
speed regulating circuit 502 includes the microprocessor 510
coupled at pin 5 to an input gate of a bidirectional or bilateral
triode thyristor 512 (sometimes called a TRIAC) via a resistor 514.
The anodes of the TRIAC are coupled to the primary coil (PRI) and
to system ground (GND), respectively. Thus, when the microprocessor
510 selectively actuates or triggers the input gate of the TRIAC
512, energy received at the TRIAC from the primary coil PRI is
driven to ground GND, thereby inhibiting sparking at the spark plug
and consequently slowing the engine speed. Later, the
microprocessor 510 may selectively actuate higher engine speed by
ceasing to actuate or trigger the TRIAC gate; consequently, primary
coil energy PRI will not be driven to ground GND, the spark plug
will fire again, and the engine speed will increase.
[0069] In the present implementation, the microprocessor 510 also
receives data associated with the speed of the engine via pin
6--pin 6 being coupled to AC_IN (or node N.sub.1) via resistor 516.
Using the voltage (or current) received at pin 6 and a known value
of resistor 516, the microprocessor 510 is configured to calculate
current engine speed. Thus, when the engine speed exceeds a desired
maximum threshold, the microprocessor 510 selectively may trigger
the TRIAC 512 to dump power to ground GND. Likewise, when the
microprocessor 510 determines the engine speed has fallen below a
desired minimum threshold, the microprocessor 510 may cease
triggering the TRIAC 512 so that the TRIAC no longer drains power
to GND.
[0070] In at least one embodiment, the power circuit 504 includes a
diode 520, a transistor 522 (e.g., a PNP transistor having emitter
E, collector C, and base B), and a protection circuit 524. The
emitter E is coupled to both pin 8 (or mGND) of the microprocessor
510 and a capacitor 526 (which in turn is coupled to node N.sub.3
or ground GND). In this circuit embodiment, pin 8 (mGND) may be
some negative voltage (e.g., approximately -4V), while pin 1 (Vcc
or GND) may be approximately 0V.
[0071] The collector C is coupled between a resistor 528 and an
anode of diode 520--a cathode of the diode 520 being coupled to
node N.sub.1. Base B (node N.sub.2) is coupled to an opposite end
of resistor 528 and also a cathode of a thyristor 530 of circuit
524. In operation, current may flow through the emitter E and base
B (and ultimately diode 520) during negative portions of the AC
signal--e.g., drawn through diode 520 by the AC signal. And in
general, capacitor 526 becomes charged by the AC signal and the
voltage of capacitor 526 serves as the input voltage to pin 8 of
the microprocessor 510. Consequently, the microprocessor 510 may be
configured to thereby provide a negative voltage trigger signal to
the TRIAC 512. A negative trigger at the TRIAC may enable the TRIAC
to pass through to ground GND both positive and negative portions
of the AC voltage received at the primary coil PRI; if the TRIAC
512 were triggered by a positive voltage, then, in some
implementations, both positive and negative portions of the AC
voltage might not be shorted.
[0072] Protection circuit 524 includes the thyristor 530, a zener
diode 532, and the capacitor 526. A cathode of the zener diode 532
is coupled to ground GND (or node N.sub.3), whereas an anode
thereof is coupled to an input gate of the thyristor 530 (via a
resistor 536) so that when the voltage across zener diode 532
exceeds the so-called breakdown voltage or threshold, the thyristor
530 is triggered. In operation, when the charge on the capacitor
526 exceeds the breakdown threshold (e.g., about -4V), then the
thyristor 530 is triggered and current can flow through the
thyristor 530 (anode to cathode), thereby inhibiting further charge
on capacitor 526. During this time, the charge of capacitor 526 may
not charge, but may drain--e.g. powering the microprocessor 510
until the voltage of capacitor 526 is less than the breakdown
voltage, at which time the thyristor 530 once again may inhibit
current flow (anode to cathode)--e.g., the thyristor 530 may be a
"gate turn-off" or GTO thyristor. Thus, the power circuit 504
provides power to the microprocessor 510, and the protection
circuit 524 prevents the microprocessor 510 from a potentially
damaging overvoltage scenario.
[0073] The clock circuit 506 includes an external oscillator 540
coupled to the microprocessor 510 at pins 2, 3 and 8 for improved
clocking to aid in detecting engine speed, although this
arrangement is optional and may be omitted (see for example FIG. 27
discussed below).
[0074] The programming circuit 508 is configured to tune the
microprocessor 510 to operate with a different desired engine
speed. For example, currently the microprocessor 510 will trigger
the TRIAC 512 at a predetermined engine speed; however, in some
embodiments a different predetermined engine speed may be desired
instead. Thus, circuit 508 enables programmability of the engine
speed used to trigger the TRIAC 512. The programming circuit 508 is
optional and also may be omitted.
[0075] As discussed above, the microcontroller 510 may provide a
negative voltage to the gate of the TRIAC 512 when it is desired to
prevent a spark event which prevents a combustion event within the
engine and has the effect of reducing engine power and speed. The
microcontroller 510 may monitor engine speed as a function of AC_IN
signal generated by magnets associated with the engine flywheel.
When an engine speed above a threshold is determined, the output
may be provided to the TRIAC gate to short the primary coil PRI and
pass energy therein to ground, and this is accomplished without a
battery and without a relay which can be expensive and not reliable
over time. The engine speed may be limited in this way for any
desired reason, including prevention of damage to the engine or
otherwise. The primary coil PRI may be grounded in this way for all
or any at least some engine cycles (e.g. every 1 out of 3 cycles or
the like) until the engine speed is at or below the threshold
speed, or until some other engine speed is attained, as
desired.
[0076] FIG. 27 illustrates another embodiment of the circuit shown
in FIG. 26; however, circuit 500' in FIG. 27 includes, among other
things, a kill switch circuit 550. As described below, when the
kill switch circuit 550 is activated, further ignition events are
prevented so that the engine will cease operating. More
particularly, circuit 550 includes an actuatable switch 554 coupled
to ground GND and two resistors 556, 558, wherein resistor 556 is
coupled to pin 2 of microprocessor 510 and resistor 558 is coupled
to pin 3 thereof. The resistors 556, 558 may be arranged as a
voltage divider so that when switch 554 is closed, the voltage at
pin 2 or pin 3 indicates a power OFF condition at the
microprocessor 510, and consequently, the microprocessor 510
actuates the TRIAC 512 at pin 5 (via resistor 514').
[0077] As illustrated in FIG. 27, the TRIAC 512 in circuit 500' is
coupled directly to the AC_IN via node N.sub.1 (e.g., instead of
the primary coil PRI, as it was in FIG. 26). Thus, when the
microprocessor 510 triggers or actuates the TRIAC 512, the TRIAC
drives the AC_IN to ground GND (e.g., instead of driving the
primary coil PRI to ground). In some implementations, it may be
desirable to trigger TRIAC 512 intermittently--e.g., in order
ensure the microprocessor 510 remains powered until the AC_IN
voltage drops to zero. For example, it may be desirable to provide
some power to the power circuit 504 while the crankshaft slows
down. It should be appreciated that if the TRIAC 512 is driven to
ground GND without intermittent triggering, all current by-passes
circuit 504; therefore, the microprocessor 510 may become unpowered
once capacitor 526 rises above a predetermined threshold (recall:
microprocessor 510 is powered by a negative voltage). Thus, by
intermittently triggering TRIAC 512, the power circuit 504 may
continue to charge and microprocessor 510 may be sufficiently
powered to control the TRIAC 512 until the ignition circuit ceases
to generate power and the engine is unpowered or `killed.` Of
course, once the AC_IN also drops below a predetermined voltage,
the power circuit 504 also will have insufficient power to keep the
microprocessor 510 powered on, and consequently, the microprocessor
510 will power OFF as well.
[0078] Circuit 500' may include additional features as well. For
example, circuits 560, 562 are adapted to provide filtering
characteristics to improve operation of the microprocessor 510
(e.g., smoothing the AC signal, minimizing undesirable noise,
etc.). For example, circuit 560 includes a resistor and capacitor
arranged in parallel between node N.sub.5 (which powers the
microprocessor at pin 8) and node N.sub.6 (e.g., pin 1 (Vcc) or
GND). Similarly, circuit 562 includes a resistor and capacitor
arranged in parallel between node N.sub.5 and node N.sub.7 (which
is coupled to pin 6 of the microprocessor 510 and also node N.sub.1
(via resistor 516)). These filtering circuits may or may not be
required in all embodiments.
[0079] While the forms of the invention herein disclosed constitute
presently preferred embodiments, many others are possible. It is
not intended herein to mention all the possible equivalent forms or
ramifications of the invention. It is understood that the terms
used herein are merely descriptive, rather than limiting, and that
various changes may be made without departing from the spirit or
scope of the invention.
* * * * *