U.S. patent number 3,651,793 [Application Number 05/009,282] was granted by the patent office on 1972-03-28 for arrangement for limiting the speed of internal combustion engines.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Gerd Hohne, Jorg Issler, Helmut Roth, Gerhard Sohner.
United States Patent |
3,651,793 |
Roth , et al. |
March 28, 1972 |
ARRANGEMENT FOR LIMITING THE SPEED OF INTERNAL COMBUSTION
ENGINES
Abstract
An arrangement through which the speed of an internal combustion
engine is limited by inhibiting the generation of ignition or fuel
injection pulses. An alternating current voltage generator is
driven from the crank shaft of the engine and provides a voltage
signal which is dependent upon the speed of the engine. A
monitoring unit connected to the voltage generator provider pulses
with amplitudes or pulse levels dependent upon the speed of the
engine. When the amplitudes of the pulses exceed a predetermined
magnitude corresponding to a predetermined engine speed, an
electronic switch becomes actuated so that electrical pulses used
for ignition and fuel injection are inhibited. Inhibition of the
pulses takes place during a time interval determined by a
monostable multivibrator, with the time interval being at least as
long as necessary for suppressing the next oncoming pulse used for
ignition or fuel injection purposes. BACKGROUND OF THE INVENTION
The present invention resides in an internal combustion engine with
a monitoring arrangement for limiting the rotational speed of the
engine. The arrangement has, furthermore, a unit for ignition and
fuel injection, which are rendered ineffective when the maximum
permissible rotational speed is exceeded. The internal combustion
engine becomes provided, for this reason, with a monitoring unit
for purpose of limiting the rotational speed. This arrangement is
intended to avoid the destruction of parts as a result of
overloading due to increase rotational speed. An internal
combustion engine is known in the art which has a monitoring unit
for limiting the rotational speed through a centrifugal force
regulator which actuates a short-circuiting switch. This switch
lies in the circuit of the ignition interrupter or circuit breaker,
and becomes closed when the maximum permissible speed is exceeded.
In this conventional case, no further ignition prevails, since the
ignition circuit breaker or interrupter is short-circuited and is
rendered, thereby, ineffective. When the engine has a plurality of
cylinders, the short-circuiting switch is connected in series with
a control switch which provides for suppression of the ignition in
only a few of the available cylinders, so that a relatively soft
limiting of the rotational speed is realized. In the preceding
conventional monitoring arrangement for the regulation of speed of
an engine, it is possible that when opening the short-circuiting
switch, an ignition cycle is produced at the improper instant of
time, so that damaging effects result. Furthermore, the monitoring
function can be easily interfered with through soiling and wear of
the switching contacts. Finally, the setting of the centrifugal
regulator corresponding to the maximum permissible speed is a
complex procedure, and as a result the desired limiting effect
cannot be attained with assurance and reliability in each case.
Accordingly, it is an object of the present invention to provide an
internal combustion engine which has means for ignition and fuel
injection, and which is provided with a monitoring unit for
limiting the rotational speed, so that the disadvantages of the
aforementioned conventional arrangement are avoided. The object of
the present invention is achieved by providing a control voltage
generator from which a monitoring pulse may be derived for the
initiating of each ignition or fuel injection cycle. The amplitude
of the monitoring pulse is made dependent upon the rotational
speed. When this amplitude of the monitoring pulse corresponds to a
level which exceeds the maximum permissible rotational speed, an
electronic protective circuit path is actuated in the monitoring
arrangement. When thus actuated, the monitoring pulse is
intercoupled with the ignition or fuel injection arrangement. A
monostable multivibrator maintains the protective circuit path in
actuated state, so that within the period of the monostable
multivibrator, the time of the multivibrator coincides with the
following pulses for initiating the ignition of fuel injection
cycles. SUMMARY OF THE INVENTION An arrangement for limiting the
speed of an internal combustion engine by inhibiting the ignition
or fuel injection pulses. A voltage generator in the form of an
alternating current generator is mechanically coupled to the engine
and produces a cyclic voltage from which monitoring pulses are
derived. The amplitudes of the monitoring pulses are made dependent
upon the rotational speed of the engine, and when the speed exceeds
a predetermined magnitude, the level of the pulses also exceed a
predetermined magnitude. A transistor switch becomes actuated when
the monitoring pulses exceed the predetermined magnitude in
amplitude, and thereby prevents the application of further ignition
or fuel injection pulses by short-circuiting the alternating
current generator. A monostable multivibrator is also actuated so
that inhibition of the ignition or fuel injection pulses is
realized for at least a time interval corresponding to the
prevalence of the next oncoming ignition or fuel injection pulse.
The alternating current generator may be one in which the rotor is
unsymmetrically mounted with respect to the stator poles. The novel
features which are considered as characteristic for the invention
are set forth in particular in the appended claims. The invention
itself, however, both as to its construction and its method of
operation, together with additional objects and advantages thereof,
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawing.
Inventors: |
Roth; Helmut (Stuttgart O,
DT), Sohner; Gerhard (Geradstetten, DT),
Hohne; Gerd (Ludwigsburg, DT), Issler; Jorg
(Stuttgart, DT) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DT)
|
Family
ID: |
5724968 |
Appl.
No.: |
05/009,282 |
Filed: |
February 6, 1970 |
Foreign Application Priority Data
|
|
|
|
|
Feb 12, 1969 [DT] |
|
|
P 19 06 883.8 |
|
Current U.S.
Class: |
123/335;
123/352 |
Current CPC
Class: |
F02D
9/00 (20130101); F02D 41/0205 (20130101); F02D
2700/0238 (20130101) |
Current International
Class: |
F02D
9/00 (20060101); F02D 41/02 (20060101); F02d
011/10 () |
Field of
Search: |
;123/102,32AE,148E,198D,198DA,198DB |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Claims
What is claimed as new and desired to be protected by Letters
Patent is:
1. An arrangement for limiting the speed of an internal combustion
engine, comprising, in combination, oscillating-voltage generator
means coupled with a shaft driven by said engine, and adapted to
provide an oscillating voltage whose amplitude is representative of
engine speed; combustion control means connected with said
generator means and adapted to produce combustion control signals,
timed with rotation of said shaft, for producing combustion in the
engine; electronic protective circuit means adapted, when actuated,
to turn off said combustion control means; threshold-detecting
means adapted to produce threshold signals in response to
generation by said generator means of a voltage beyond a
predetermined value, said predetermined value corresponding to the
maximum engine speed permissible; trigger means adapted to produce
trigger pulses in response to said threshold signals; and timing
means actuated in response to some of said trigger pulses and
serving to switch on said protective circuit means.
2. An arrangement as defined in claim 1; and further comprising
differentiating means associated with said trigger means and
adapted to produce trigger pulses having the form of voltage
spikes.
3. The arrangement as defined in claim 1, wherein said combustion
control means comprises ignition pulse generating means for
igniting the fuel-air mixture within the cylinders of said
engine.
4. The arrangement as defined in claim 1, wherein said combustion
control means comprises fuel injection pulse generating means for
the injection of fuel into said engine.
5. The arrangement as defined in claim 1 wherein said timing means
comprises a monostable multivibrator.
6. The arrangement as defined in claim 1 wherein said protective
circuit means comprises a transistor with emitter-collector path in
parallel with said voltage generating means and base connected to
said timing means, said emitter-collector path being in the
conducting state during said interval of said timing means.
7. The arrangement as defined in claim 1, including diode means
connected in series with said emitter-collector path of said
transistor.
8. The arrangement as defined in claim 1 including a source of DC
voltage; and voltage stabilizing means associated with said
threshold-detecting means and connected to said source of DC
voltage for providing a source of constant voltage.
9. The arrangement as defined in claim 1 wherein said timing means
comprises a monostable multivibrator with adjustable resistor means
for varying the on time duration of said protective circuit.
10. The arrangement as defined in claim 1 including at least one
diode connected to said threshold detecting means.
11. The arrangement as defined in claim 1 wherein said detecting
means comprises at least one zener diode.
12. The arrangement as defined in claim 1 wherein said threshold
means comprises at least one diode connected in series with a zener
diode.
13. The arrangement as defined in claim 1 including at least one
adjustable resistor connected to said threshold detecting
means.
14. The arrangement as defined in claim 1 including at least one
temperature dependent resistor connected to said threshold
detecting means.
15. The arrangement as defined in claim 1 wherein said temperature
dependent resistor controls the cylinder temperature of said
engine.
16. The arrangement as defined in claim 1 wherein said threshold
detecting means comprises a plurality of switching elements with
different threshold values; and selector means for selecting a
predetermined one of said threshold elements with a predetermined
threshold value.
17. The arrangement as defined in claim 1 wherein said voltage
generating means comprises an alternating current generator whereby
a plurality of pulses are generated for one revolution of said
alternating current generator, said plurality of pulses during one
revolution of said rotor having different amplitudes for a
predetermined speed of said engine.
18. The arrangement as defined in claim 1 wherein said voltage
generating means comprises an alternating current generator with
magnetic field generated through at least one oxide magnet.
19. An arrangement for limiting the speed of an internal combustion
engine, comprising, in combination, voltage generating means
coupled to the crank shaft of said engine and providing a voltage
signal with amplitude dependent upon the speed of said engine, said
amplitude exceeding a predetermined level when said speed exceeds a
predetermined magnitude; electronic switching means connected to
said voltage generating means and actuated when said amplitude
exceeds said predetermined level, said switching means providing
upon being actuated a regulating signal representing that the speed
of said engine is above said predetermined magnitude; engine
control means connected to said voltage generating means and
applying controlling pulses from said voltage signal to said engine
for controlling the speed of said engine, the speed of said engine
being dependent on the pulse repetition frequency of said
controlling pulses; inhibiting means connected between said
switching means and said engine control means and actuated by said
regulating signal, said inhibiting means inhibiting the application
of said controlling pulses to said engine when actuated by said
regulating signal; and timing means connected to said switching
means for maintaining said switching means actuated for an interval
so that at least the next controlled pulse to be applied to said
engine is inhibited, whereby inhibiting the application of said
controlling pulses to said engine reduces the speed of said engine,
said voltage generating means comprising an alternating current
generator providing an alternating current having a cycle
constituted of two half-waves, the leading half-wave being the
source for said signal amplitude for actuating said switching means
means and the trailing half-wave being the source of said
controlling pulses.
20. An arrangement for limiting the speed of an internal combustion
engine, comprising, in combination, voltage generating means
coupled to the crank shaft of said engine and providing a voltage
signal with amplitude dependent upon the speed of said engine, said
amplitude exceeding a predetermined level when said speed exceeds a
predetermined magnitude; electronic switching means connected to
said voltage generating means and actuated when said amplitude
exceeds said predetermined level, said switching means providing
upon being actuated a regulating signal representing that the speed
of said engine is above said predetermined magnitude; engine
control means connected to said voltage generating means and
applying controlling pulses from said voltage signal to said engine
for controlling the speed of said engine, the speed of said engine
being dependent on the pulse repetition frequency of said
controlling pulses; inhibiting means connected between said
switching means and said engine control means and actuated by said
regulating signal, said inhibiting means inhibiting the application
of said controlling pulses to said engine when actuated by said
regulating signal; and timing means connected to said switching
means for maintaining said switching means actuated for an interval
so that at least the next controlling pulse to be applied to said
engine is inhibited, whereby inhibiting the application of said
controlling pulses to said engine reduces the speed of said engine,
said voltage generating means comprising an alternating current
generator whereby a plurality of pulses are generated for one
revolution of said alternating current generator, said plurality of
pulses during one revolution of said rotor having different
amplitudes for a predetermined speed of said engine, the rotor of
said current generator being unsymmetrically mounted with respect
to the stator poles of said alternating current generator, the
radial lengths from the rotational axis of said rotor to the stator
poles of said generator being different for each pole of the
stator.
Description
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a circuit diagram and shows the monitoring arrangement
for limiting the speed of an internal combustion engine;
FIG. 2 is an isometric view with partial cross section of a voltage
generator used in conjunction with the arrangement of FIG. 1;
and
FIG. 3 is a circuit diagram for using the monitoring arrangement of
FIG. 1 in conjunction with a fuel injection arrangement.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawing and in particular to FIG. 1, an internal
combustion engine B is used for driving a motor vehicle, not shown,
and a monitoring unit W is used to limit the speed of the engine.
The limiting of the speed is accomplished in a manner whereby
combustion control means, e.g., an ignition arrangement Z,
associated with the internal combustion engine B is disconnected or
rendered inoperative through the monitoring unit W, when the speed
exceeds a predetermined maximum permissible value.
The internal combustion engine B is, for example, equipped with a
conventional coil ignition arrangement. This ignition arrangement Z
has a circuit junction 11 which leads to the positive terminal of a
DC current source 14, by way of the circuit path 12 and the switch
13 in the form of an operating switch. The DC current supply 14 is
provided with a battery of the motor vehicle. The negative terminal
of this DC current source or battery 14 is connected to ground
potential. A negative circuit path 15 applies ground potential to
the circuit junction or terminal 16 of the ignition arrangement Z.
Connected between the circuit junctions or terminals 11 and 16 of
the ignition arrangement Z, is a series combination of the
emitter-collector path 17-18 of a transistor 19 and the primary
winding 20 of an ignition coil 21. One terminal of the secondary
winding 22 of the ignition coil 21, is connected to both the
circuit junction 16 and to one terminal of a spark plug 23. The
second terminal of the secondary winding 22 is connected, on the
other hand, to the other terminal of the spark plug 23. A
monostable multivibrator 24 is, furthermore, connected across the
terminals or circuit junctions 11 and 16. The control input 25 of
the ignition arrangement Z is applied to the monostable
multivibrator 24, through the circuit path 26 which, in turn, leads
to the base 27 of the transistor 19.
The control input 25 of the ignition arrangement Z is connected to
the output 29 of a control voltage generator 30 which has one
terminal 31 connected to ground potential through the circuit path
32.
A substantially small alternating current generator is used for the
control voltage generator 30, and is coupled to the crank shaft K
of the engine B through linkage denoted in the drawing by dash-dot
lines. The alternating current generator provides an AC voltage
with amplitude dependent upon the rotational speed of the crank
shaft. The positive half-wave 34 is used, in this embodiment, for
providing the ignition pulse, whereas the negative half-wave 33 is
used as a monitoring pulse in the monitoring unit W.
The principle of the speed regulation through the monitoring unit W
resides on the basis that when the monitoring pulse has an
amplitude exceeding the maximum permissible level, corresponding to
the maximum permissible speed, an electronic protection circuit H
is actuated. In the actuated state of the circuit H, the ignition
arrangement Z is interconnected, so that the ignition pulse for
this ignition arrangement is held up through a predetermined state
of a monostable timing means, such as a multivibrator, M. This
ignition pulse is thus held up for a period of time extending at
least for the duration of the ignition pulse.
The monitoring unit W has a first power supply line 35 provided
with a circuit junction or terminal 36, and a second power supply
line 37 provided with a circuit terminal or junction 38. The
circuit junction 36 of the first power supply line 35 is
connectable to the positive terminal of the direct current source
14, through the operating switch 13. The circuit terminal 38, on
the other hand, and associated with the second power supply line
37, is connected to ground potential.
In order to provide for constant voltage supply, the monitoring
unit W is equipped with a voltage stabilizer G at its input. This
voltage stabilizer G includes a zener diode 39 with anode connected
to the circuit junction or terminal 38 of the second power supply
line 37. The cathode of the zener diode, on the other hand, leads
to the circuit junction 36, through a resistor 40. In addition, the
voltage stabilizer G includes a stabilizing transistor 41 with base
42 connected to the cathode of the zener diode 39. The
emitter-collector path 43-44 of the transistor 41, is connected in
series with the power supply line 35. The emitter 43 of the
transistor is connected in series with a capacitor 45 leading, in
turn, to the power supply line 37.
The monitorin unit W contains, moreover, a threshold-detecting
control input branch E which has one terminal connected to the
first power supply line 35, and another terminal connected to the
circuit junction 46. The circuit junction 46 is connected directly
to the output terminal 29 of the voltage generator 30. At least one
threshold-detecting switching element 47 is provided in the control
branch E, and has a predetermined threshold value. This switching
element 47 is switched to the conducting state when the applied
voltage to the monitoring pulse exceeds the threshold value
associated with this switching element. The threshold value of this
element 47 is made such that it corresponds to maximum permissible
rotational speed.
In an exemplary case, the switching element 47 with a predetermined
threshold value is in the form of a zener diode. The switching
element can, however, also be constructed through a plurality of
series connected zener diodes 47, 47' and 47", as represented by
dashed lines in the drawing. Aside from this, it is also possible
to use a single diode 48 or a chain of series-connected diodes 48,
48', 48" which are also shown in dashed or broken lines.
Assume that the engine B drives a load L through a conventional
gear shift arrangement R, as is the usual case in motor vehicles.
Under these conditions, it is possible to link the gear shift R to
a switching arrangement which includes of number of switching
elements 47, 47a, 47b . . . which exhibit different threshold
values. The arrangement is such that when the gear shift R shifts
to another gear stage, a different one of the switching elements
47a, 47b . . . becomes correspondingly switched into the circuit.
The rotational speed can then become limited in another manner
through the individual gear stages. The switching function can be
accomplished whereby a selector switch 49 is used with a movable
contact arm 50 denoted by dash-dot lines. This movable arm 50 is
connected to the shifting lever 51 used to shift gears. At the same
time, the movable arm 50 may be brought into electrical contact
with a plurality of fixed contacts 52, 52a, and 52b which are, in
turn, connected to respective switching elements 47, 47a, 47b. The
other terminals of these switching elements are connected jointly
and to the circuit junction 46, and the movable contact arm 50 also
leads to the second power supply line 35.
It is further desirable to provide a monitoring resistor 53 in the
form of an adjustable resistor, in the threshold-detecting control
branch E. This adjustable resistor 53 allows precise setting of the
level corresponding to the maximum permissible speed. In a
particular case, it is also possible to couple the sliding contact
54 of the adjustable resistor 53, to the shifting lever 51 for
regulation purposes.
It is also possible to provide a temperature dependent resistor 55
in the control input branch E. This temperature dependent resistor
55 is situated so that it is influenced preferably from the thermal
state of the internal combustion engine B. As a result of such an
arrangement, the speed limitation or regulation is attained whereby
such speed regulation is made dependent upon the temperature of the
engine B.
The control branch E is connected to the first power supply line 35
to a resistor 56 which is also in the form of an adjustable
resistor and establishes the circuit potential P at the base 60 of
the transistor 57.
In the simplest case, the monostable multivibrator M can be
directly controlled from the circuit point P. It is, however, more
advantageous to connect the monostable multivibrator M to the
circuit point P, through a trigger stage T subjected to
rectangular-shaped trigger pulses, and a differential network D.
With this arrangement, each monitoring pulse from the monitoring
arrangement W can be processed with reliability.
The trigger stage T has a first triggering transistor 57, a second
transistor 58, and a control transistor 59. The base 60 of the
first triggering transistor 57 is connected to the circuit point P,
whereas the emitter of this transistor is connected to the second
power supply line 37. The collector 62 of this transistor 57 is
connected directly to the base 63 of the second trigger transistor
58, while it is simultaneously connected to a resistor 64 leading
to the first power supply line 35. The second triggering transistor
58 has its emitter 65 also connected to the second power supply
line 37, whereas the collector 66 is directly connected to the base
67 of the control transistor 59, as well as to a resistor 68
leading to the first power supply line 35. The control transistor
59 has its collector 69 connected to the first power supply line
35, whereas its emitter 70 leads to the second power supply line 37
through a resistor 71.
The differentiating network D is formed through a capacitor 72
having one electrode connected to the emitter 70 of the control
transistor 59. The other electrode of this capacitor 72 is joined
to a circuit junction F. Connected to this circuit junction F, is
the monostable multivibrator M. The arrangement is such that when
the trigger pulse is differentiated, the voltage spike resulting
from the trailing edge, switches the monostable multivibrator M to
the "on" state. The spike voltage resulting from the
differentiating process of the leading edge of the trigger pulse,
on the other hand, terminates the "on" state of the monostable
multivibrator when the latter has not already returned to its
initial state.
The monostable multivibrator M contains a first switching
transistor 73 and a second switching transistor 74. The base 75 of
the first transistor 73 is connected to the circuit junction F to
which also a resistor 76 is connected. The other terminal of this
resistor 76 is joined to the second power supply line 37. The
circuit junction F and hence the base 75 of the transistor 73 is
also connected to the collector 78 of the second transistor 74,
through a resistor 77. The emitter 79 of the first transistor 73 is
connected also to the circuit junction F through a capacitor 80
which serves to bypass disturbing pulse signals. This emitter 79,
at the same time, leads to the second voltage supply line 37
through a resistor 81. The collector 82 of the first switching
transistor 73 is joined to the first power supply line 35, through
a resistor 83, while this collector is coupled to the base 85 of
the transistor 74, through a coupling capacitor 84. Aside from
this, the base 85 of the second switching transistor 74 also leads
to the first power supply line 35 through a resistor 86. This
resistor 86 forms a timing network together with a coupling
capacitor 84, which has a duration corresponding to the duration of
the interval of the monostable multivibrator. The resistor 86 is
made variable or adjustable so that the time interval may be
precisely set in a simple manner. The second switching transistor
74 has its emitter 87 directly connected to the second power supply
line 37, while the collector 78 of this transistor 74 is connected
to the first supply line 35, through a resistor 88.
The electronic protective circuit path H for limiting the
rotational speed, is formed from a transistor 91 having an
emitter-collector path 89-90. The base 92 of the transistor 91 is
directly connected to the emitter 79 of the switching transistor
73, whereas the emitter 89 is connected to the second power supply
line 37 and hence to ground potential. The collector 90 of the
transistor 91 is connected in series with a diode 93 which, in
turn, is connected directly to the control output terminal 29 of
the voltage generator 30, by being connected to the terminal 46 of
the control input branch E.
In operation of the arrangement of FIG. 1, the operating switch 13
becomes closed for the purpose of operating the driving engine B,
and as a result voltage from the DC source 14 is applied to the
ignition arrangement Z with terminals 11 and 16, as well as the
monitoring unit with terminals 36 and 38 used to monitor and
regulate the rotational speed. The emitter-collector path 17-18 of
the pnp switching transistor 19 is normally conducting in the
ignition arrangement Z. Accordingly, current flows, in this state
of operation, through the primary winding 20 of ignition coil 21.
At the instant of ignition, the positive half-wave 34 appears at
the control output terminal 29 of the voltage generator 30. This
half-wave 34 reaches, in the form of an actuating pulse, to the
control input 25 of the ignition arrangement Z, through the circuit
path 28. From there, the actuating pulse reaches the base 27 of the
switching transistor 19, through the monostable multivibrator 24
lying within the circuit path 26. The applied signal to the base 27
causes the potential of this base to become positive to the extent
that its emitter-collector path 17-18 of the transistor 19 becomes
cutoff or nonconducting. Current flow in the primary winding 20 of
the ignition coil 21 becomes thereby interrupted, and as a result a
high voltage pulse is generated in the secondary winding 22. Due to
the high voltage pulse induced in the secondary winding 22, an
igniting spark appears across the spark plug 23, and the compressed
fuel-air mixture within the cylinder becomes thereby ignited. With
the aid of the monostable multivibrator 24, the emitter-collector
path 17-18 of the switching transistor 19 is maintained
nonconducting until the high voltage pulse has again become
terminated.
The negative half-wave 33 which precedes the positive half-wave 34
at the control output terminal 29 of the generator 30 described
above, reaches the terminal 46 of the control input branch E of the
monitoring arrangement W, and serves as a monitoring pulse. For
purposes of simplicity and maintaining the description of the
embodiment in clarified form, the switching element with
predetermined threshold value is used only in the form of a single
zener diode 47.
If, now, the internal combustion engine B has exceeded the maximum
permissible rotational speed, the control voltage generator 30
provides a monitoring pulse which gives rise to a signal exceeding
the threshold value of the zener diode 47. As a result, the zener
diode 47 becomes conducting and the circuit point P becomes thereby
negative, so that the base 60 of the first NPN trigger transistor
57 also becomes negative. During the duration of the conducting
state of the zener diode 47, the emitter-collector path 61-62 of
this transistor 57 becomes cutoff or nonconducting, and the base 63
of the second NPN trigger transistor 58 becomes positive, through
the resistor 64, to the extent that the emitter-collector path
65-66 of the last-mentioned transistor 58 becomes switched to the
conducting state. Since the switching takes place very rapidly, a
substantially rectangular-shaped pulse is produced across the
resistor 68.
This pulse across the resistor 68 appears at the resistor 71 in the
form of a trigger pulse due to the use of the NPN control
transistor 59. At the same time, the emitter-collector path 65-66
of the second trigger transistor 58 conducts, and the base 67 of
the control transistor 59 becomes negative to the extent that the
emitter-collector path 70-69 attains the cutoff state. By
differentiating the trigger pulse through the differentiating
capacitor 72, a negative and afterward a positive voltage spike is
realized at the circuit junction F. If the monostable multivibrator
M is in its stable state, then this negative voltage spike has no
effect upon the multivibrator M. The monostable multivibrator is in
its stable state when the emitter-collector path 79-82 of the first
NPN transistor 73 is cutoff and the emitter-collector path 87-78 of
the second NPN transistor 74 is conducting. When, however, the
positive voltage spike appears, the potential at the base 75 of the
first transistor 73 rises briefly in positive direction to the
extent that the emitter-collector path 79-82 becomes conducting.
Following the discharge of the coupling capacitor 84, the base 85
of the second transistor 74 acquires negative potential, so that
the emitter-collector path 87-78 is cutoff or nonconducting. A
feedback effect then appears through the resistor 77 and to the
base 75 of the first switching transistor 73, whereby a rapid
switching of the multivibrator M takes place to the astable state,
as well as back to the stable state.
The duration of the switching process, or the duration in which the
emitter-collector path 79-82 of the first switching transistor 73
conducts and the emitter-collector path 87-78 of the second
switching transistor 74 is cutoff or nonconducting, is determined
by the discharging of the coupling capacitor 84 through its
capacitance value, and the magnitude of the resistor 86. When the
discharge of the coupling capacitor 84 has terminated or become
ended, the emitter-collector path 87-78 of the second switching
transistor 74 becomes again conducting, and the emitter-collector
path 79-82 of the first switching transistor 73 becomes again
cutoff or nonconducting.
Since the first switching transistor 73 conducts through its
emitter-collector path 79-82 during the preceding switching
process, the NPN transistor 91 acquires positive potential at its
base 92, so that the protective path through the emitter-collector
path 89-90 is also in the conducting state. The positive half-wave
voltage 34 can, consequently, not be effective for initiating the
ignition process during the switching step of the multivibrator M,
since this positive half-wave voltage 34 is conducted away from the
diode 93 and the emitter-collector path 89-90 of the protective
path H. Thus, the half-wave 34 is conducted to ground. Since the
fuel-air mixture in the engine B cannot be further ignited, the
rotational speed also cannot assume higher values.
When, now, the further negative half-wave voltage of the generator
30 produces a monitoring pulse with amplitude also again exceeding
the threshold value of the zener diode 47, a new trigger pulse
appears across the resistor 71 in a manner described above. Should
the switching state of the multivibrator M not yet be terminated,
whereby the first transistor 73 with its emitter-collector path
79-82 is still in the conducting state, the negative voltage spike
resulting from the differentiation of the trigger pulse at the
leading edge, takes effect. Thus, this negative spike provides for
the condition that the multivibrator M is returned to the stable
state prior to the appearance of the following positive voltage
spike. This negative voltage spike causes the base 75 of the first
switching transistor 73 to become negative to the extent that the
emitter-collector path 79-82 is again switched to the cutoff state
and the emitter-collector path 87-78 of the second switching
transistor 74 is again made conducting. As a result of these
conditions, rapidly following monitoring pulses can be processed
and evaluated through the monitoring arrangement.
If a soft speed limit is to be attained, it is necessary to care
for the condition that after exceeding the maximum permissible
speed and hence the corresponding voltage level, the ignition
processes are not entirely rendered ineffective immediately
thereafter. This is accomplished in a simple manner by providing
that a plurality of monitoring pulses are taken from the generator
30 when the latter executes one revolution. These monitoring pulses
are then set so that they have different amplitudes corresponding
to a predetermined rotational speed.
FIG. 2 illustrates an alternating current generator with the
aforementioned specification. This generator has a stator 94 with
two poles 95 and 96. The rotor 97 is mounted within the stator in
an unsymmetrical manner upon a shaft 98, and is rotatable with
respect to the fixed poles 95 and 96 of the stator. The rotor 97
consists of material which is nonmagnetic. Thus, the rotational
axis 99 of the rotor shaft 98 is displaced from the line of
symmetry 100 of these stator poles 95 and 96. The axis of rotation
99 is parallel to the line of symmetry 100. Aside from this, the
poles 101 and 102 of the rotor 97 are spaced at different radial
lengths 11 and 12, respectively. The rotor shaft 98 is surrounded
by a permanent magnet 103 which is preferably a conventional oxide
magnet. The North pole N of this permanent magnet 103 faces the
rotor 97 whereas the South pole S faces the stator 94. A coil 104
surrounding the magnet 103 provides the control voltage made
available at the terminals 29 and 31 in FIG. 1. In accordance with
this embodiment of the control voltage generator in FIG. 2, two
control voltage periods are realized during one rotation of the
rotor 97, and a negative half-wave 33 as well as a positive
half-wave 34 are realized. When such a control voltage generator is
used in accordance with the embodiment of FIG. 1, the rotor shaft
98 is driven at only half the rotational speed applied to the crank
shaft K. This results from the condition that only a single
cylinder internal combustion engine is applicable there, and
accordingly, only a single actuating pulse for initiating the
ignition and a monitoring pulse are required for one rotation of
the crank shaft K. A speed-changing mechanism 105 is, accordingly,
provided and shown in the drawing in schematic form. This
speed-changing mechanism 105 is coupled between the crank shaft K
and the rotor shaft 98, and provides for the required reduction in
rotational speed.
If, now, pole 101 of the rotor moves past the stator pole 95, and
the pole 102 of the rotor moves past the stator pole 96, then the
first control voltage period takes place. The second control
voltage period is produced when the rotor pole 101 moves past the
stator pole 96 and the rotor pole 102 moves past the stator pole
95. From the drawing, it is possible to observe that in generating
the first control voltage period, the air gap between the stator
pole 95 and the rotor pole 101 is substantially small, whereas the
air gap between the stator pole 96 and the rotor pole 102 is
relatively large. In generating the second control voltage period,
an air gap of intermediate length prevails between the stator pole
95 and the rotor pole 102, as well as between the stator pole 96
and the rotor pole 101. In this manner, it is possible to achieve
the condition wherein the magnetic stray flux and thereby the
variation in the magnetic flux is different when generating the
first control period than when the second control period prevails.
Accordingly, a first control voltage period is realized for a
predetermined rotational speed, in which the amplitude of the
half-waves are, for example, larger than those of the half-waves in
the second control period. In this case, the monitoring pulse
realized from the negative half-wave of the first control voltage
period when exceeding the maximum permissible rotational speed, is
used to influence the following ignition process. The arrangement
is such that the monitoring pulse derived from the negative
half-wave of the second control voltage period, is not sufficient
to exceed the threshold level of the zener diode 47 and thereby
affect the now-following ignition process. As a result of this
arrangement and through the preceding conditions, only a portion of
the following ignition cycles are suppressed when the maximum
permissible speed is exceeded.
This situation applies when the maximum permissible speed is
exceeded in a gradual manner.
When, however, the maximum permissible speed is exceeded suddenly
and by a substantial amount, severe braking of the engine takes
place, since all monitoring pulses will then exceed the threshold
level of the zener diodes 47 with their amplitudes, so that all
following pulses for initiating the ignition cycles are rendered
ineffective. Sudden and abrupt exceeding of the maximum permissible
speed may take place when the motor vehicle, for example, operates
in the gear-shift position and the driven wheels are lifted from
the road, or when the gear-shift lever drops out of the selected
position.
The monitoring unit W can also be operatively coupled with the unit
F.sub.0 used for fuel injection, instead of the ignition
arrangement Z. Such a fuel injection arrangement is shown in FIG.
3. The latter contains an electromagnetically actuated injection
valve 106 which is provided with a control winding 107. This
control winding 107 is connected in series with the
emitter-collector path 108-109 of an npn switching transistor 110.
The series circuit has a terminal 111 on the transistor end, and a
terminal 112 at the valve end. The base 113 of the switching
transistor 110 leads to a control input terminal 115, through a
monostable multivibrator 112. For purposes of applying supply
voltages to the monostable multivibrator 114, the latter is also
connected to the terminals 111 and 112. If, now, the injection unit
F.sub.0 is inserted in FIG. 1, in place of the ignition arrangement
Z, the positive supply line 12 is connected to the terminal 111,
and the negative supply line 15 is connected to the terminal 112,
whereas the control line 28 is connected to the control input
115.
The emitter-collector path 108-109 of the switching transistor 110
is, consequently, not conducting and the injection valve 106 is
closed, when in the normal or inoperative quiescent state. As soon
as the positive half-wave 34 generated by the control voltage
generator 30 reaches the control input 115, the base 113 of the
transistor 110 becomes positive to the extend that the
emitter-collector path 108-109 conducts and the injection valve 106
becomes thereby opened. The opening duration of the injection valve
106 and hence the quantity of injected fuel are determined by the
associated time interval of the monostable multivibrator 114. When
operating together with the monitoring arrangement W, the fuel
injection unit F differs from the ignition arrangement Z solely in
the respect that when the permissible rotational speed is exceeded,
no fuel injection cycle takes place. As a result of this feature,
no fuel-air mixture is made available within the cylinder of the
engine for ignition.
It is, of course, within the frame of the present invention that
the arrangement described above may be used in conjunction with an
internal combustion engine having a plurality of cylinders
operating in conjunction with a rotating distributor which applies
the necessary ignition pulses from the ignition coil 21 to the
individual spark plugs within the cylinders from the secondary
winding 22. For purposes of generating the control voltage, an
embodiment as shown in FIG. 2 can then also be used. It is only
necessary to provide that the rotational speed of the crank shaft K
is properly changed to drive the rotor shaft 98 through the
coupling 105. The alternating current generator used to provide the
control voltage can, at the same time, be designed so that it has a
number of stator and rotor poles corresponding to the number of
cylinders so that a direct coupling between the crank shaft K and
the rotor shaft 98 is possible. For the purpose of realizing a soft
rotational speed limiting, the stator poles can also have, for
example, elliptical surfaces, and the rotor poles may have
circumferential lines also corresponding to an ellipse.
In the embodiment of FIG. 1, furthermore, a conventional high
voltage capacitor ignition arrangement can also be used for
ignition purposes. In this case, the control input 25, for example,
leads to the control electrode of a thyristor which becomes
triggered or fired through the positive half-wave 34 from the
generator 30 when in the state of ineffective monitoring pulses.
The charged ignition capacitor is then made to discharge through
the primary winding 20 of the ignition coil 21 as a result of the
conducting state of the thyristor.
Assume that the ignition arrangement consists, for example, of two
arrangements commonly known as double-ignition arrangements. Each
of them has a control voltage generator 30 connected to a terminal
output 29 and a control input terminal 25. In such a case, the
control output terminal 29 as the terminal 46, in FIG. 1, can be
connected only to the protective path H through the diode 93 and a
control output terminal of the other voltage generator, so that
only a single monitoring unit W is used.
It will be understood that each of the elements described above, or
two or more together, may also find a useful application in other
types of constructions differing from the types described
above.
While the invention has been illustrated and described as embodied
in monitoring arrangement for speed limiting of internal combustion
engines, it is not intended to be limited to the details shown,
since various modifications and structural changes may be made
without departing in any way from the spirit of the present
invention.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can by applying current
knowledge readily adapt it for various applications without
omitting features that, from the standpoint of prior art, fairly
constitute essential characteristics of the generic or specific
aspects of this invention and, therefore, such adaptations should
and are intended to be comprehended within the meaning and range of
equivalence of the following claims.
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