Apparatus for influencing control quantities of an internal combustion engine

The invention is directed to an apparatus for influencing control quantities of an internal combustion engine by means of which vibrations of the entire vehicle in the lower engine speed range, particularly at idling, are to be eliminated. This is accomplished by allocating to each cylinder a regulating unit which regulates the control quantities influencing the respective cylinder, such as fuel metering, exhaust gas recirculation, start of injection, duration of injection, air/fuel ratio, ignition time point, et cetera, for the smoothest possible running condition.

BACKGROUND OF THE INVENTION 
In motor vehicles running in the lower speed range, particularly at idling, 
the entire vehicle is often subject to low-frequency vibrations. These 
vibrations are in the range of between 1 and 5 Hz. 
The reason for these vibrations lies in the series production of the 
fuel-injection equipment. The injection components are manufactured to 
tolerances causing different quantities of injected fuel per cylinder. 
These differences in fuel quantity result in rapid torque changes which 
excite the vibratory composite of engine and chassis. Thus, the vibrations 
are an unavoidable consequence of manufacturing tolerances. 
These low-frequency vibrations may be dampened, for example, by correcting 
the amounts of fuel to be injected into the individual cylinders. Such an 
apparatus for dampening the vibrations includes, for example, a regulator 
which, in dependence on rapid torque changes, varies a predetermined 
desired fuel value in such a manner to keep these torque changes at a 
minimum possible level. 
SUMMARY OF THE INVENTION 
It is the object of the invention to provide an apparatus for influencing 
control quantities of an internal combustion engine to correct the amounts 
of fuel to be injected into the individual cylinders fast, accurately, 
reliably and with the objective to have each cylinder deliver the same 
torque, thereby providing a smooth running condition of the engine. This 
is accomplished by providing a smooth-running regulating arrangement 
wherein each cylinder is provided with a regulating unit of its own.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Referring now to FIG. 1, reference numeral 10 identifies a smooth-running 
regulating arrangement for an internal combustion engine. The regulating 
arrangement includes a number z regulating units 11, 12 and 13, with z 
denoting the number of cylinders that the internal combustion engine has. 
Further, smooth-running regulating arrangement 10 includes z memory 
storage units 14, 15 and 16, two synchronizing devices 17 and 18, as well 
as a device 19 for forming a mean value. For a better understanding of the 
smooth-running regulating arrangement 10, FIG. 1 also shows an idle-speed 
regulator 20, a control unit 21 which is dependent on the position of the 
accelerator pedal, a fuel-metering apparatus 22, and the internal 
combustion engine 23. 
The z regulating units 11, 12 and 13 are connected to their associated z 
memory storage units 14, 15 and 16, respectively, and to the output of 
mean-value device 19. Device 19 has applied to its input the output 
signals from all z memory storage units 14 to 16. The inputs of the z 
memory storage units 14 to 16 are connected to synchronizing device 17; 
whereas, the outputs of the z regulating units 11 to 13 are connected to 
synchronizing device 18. The two synchronizing devices 17 and 18 are 
activated by a signal dependent on the internal combustion engine 23. 
Internal combustion engine 23 is connected to fuel-metering control 
apparatus 22 which, in turn, is connected to synchronizing device 18, 
idle-speed regulator 20 and accelerator-dependent control unit 21. 
The mode of operation of the smooth-running regulating arrangement of FIG. 
1 can best be described with reference to the timing diagram of FIG. 2. 
FIG. 2 illustrates the timing diagram of a four-cylinder internal 
combustion engine. It shows the time span covering two crankshaft 
revolutions, that is, a crank angle of 720.degree. . In this time span, 
each one of the four cylinders has experienced one combustion. 
In this timing diagram, I and J identify two actual-value signals that are 
generated by means of a segmented wheel 9. This wheel 9 is connected with 
the crankshaft and has four segments symmetrically spaced over its 
periphery. Each pulse of the actual-value signal J corresponds to one 
wheel segment. The length of each pulse of actual-value signal J 
corresponds to the length of time a segment of the wheel takes to traverse 
an imaginary plane perpendicular to the segmented wheel 9. Since four 
segments of the wheel traverse the imaginary plane during one crankshaft 
revolution, yet with only two combustions occurring in the cylinders 
during this time, it is exactly two segments of the wheel that traverse 
the imaginary plane perpendicular to the wheel between two combustions. 
Accordingly, the time span between two combustions is subdivided into two 
time periods by means of these two wheel segments. 
In view of the symmetrical configuration of the segmented wheel and 
considering that the crank angle velocity immediately following a 
combustion is always somewhat higher than immediately prior to a 
combustion, these two time periods, for example, J21 and J22, are always 
of different magnitude. Therefore, the shorter one of the two time 
periods, for example, J21, will always indicate that a combustion has 
occurred; whereas, the longer one of the two time periods, for example, 
J22, will indicate that a combustion is about to occur. 
After a one-time adjustment of the segmented wheel on the crankshaft, the 
actual-value signal J thus permits an accurate determination of the 
simulated combustion time points V of the individual cylinders, which are 
also referred to as synchronizing signals. The timing diagram of FIG. 2 
shows the combustion time points V of the individual cylinders and their 
relationship to the actual-value signal J. 
The determination of the combustion time points V from actual-value signal 
J is performed in the two synchronizing devices 17 and 18 of FIG. 1. By 
means of the simulated combustion time points V, synchronizing device 17 
directs the actual values I1, I2 and Iz to their associated memory storage 
units 14, 15 and 16, respectively; whereby, these actual values I1, I2 to 
Iz are likewise generated by synchronizing device 17 with the aid of 
actual-value signal J. Actual values I1, I2 to Iz reflect the durations of 
time between two combustion time points, as illustrated in FIG. 2. 
Equally, synchronizing device 18 determines, with the aid of actual-value 
signal J, the simulated combustion time points V and switches the 
correcting quantities S1, S2 and Sz formed by regulating units 11, 12 and 
13, respectively, to fuel-metering apparatus 22 as correcting signal S. 
Correcting signal S is illustrated in the timing diagram of FIG. 2. It is 
made up of correcting quantities S1, S2 to Sz of the individual cylinders, 
these quantities being generated by the regulating units corresponding 
thereto. Thus, for example, correcting quantity S1 is produced by 
regulating unit 11 from actual value I1 buffered in memory storage unit 14 
and a mean value Mz. Mean value Mz is formed by mean-value device 19 from 
all buffered actual values I1, I2 to Iz. 
If, for example, the internal combustion engine is at time T as illustrated 
in the timing diagram of FIG. 2: first, a combustion occurs in cylinder 2 
in this instant; second, synchronizing device 17 delivers actual value I1, 
that is, the duration of time between the combustion in cylinder 1 and the 
combustion in cylinder 2, to memory storage unit 14; and, third, 
synchronizing device 18 directs correcting quantity S3 to fuel-metering 
apparatus 22 for the next combustion in cylinder 3. This switching of 
correcting quantity S3 takes place a short time after T to enable the 
associated regulating unit to adjust this new correcting quantity. As a 
result, this new correcting quantity is dependent on all preceding actual 
values. 
Thus, the entire smooth-running regulating arrangement 10 produces from an 
actual-value signal I obtained by means of a segmented wheel, a correcting 
signal S for input into the fuel-metering apparatus 22. Where applicable, 
further inputs from an idle-speed regulator 20 and/or an 
accelerator-dependent control unit 21, for example, may also influence the 
apparatus 22. Fuel metering apparatus 22 then uses these input signals for 
determination of, for example, the quantity of fuel to be injected into 
the internal combustion engine 23. 
Since the regulating units 11 to 13 and the idle-speed regulator 20 may be 
integral-action regulators, for example, the case may occur that these two 
integral-action components operate in opposition to each other. To avoid 
this, it is necessary for the smooth-running regulating arrangement 10 to 
be incorporated into the entire injection system of the internal 
combustion engine. This is possible, for example, because the 
smooth-running regulating arrangement 10 can only dynamically influence 
the entire injection system. For this dynamic influence, it is then 
necessary for the sum of the correcting quantities S1 to Sz to be equal to 
zero, that is, the mean-fuel quantity which, as a result of the 
smooth-running regulation, is delivered to the internal combustion engine 
as a decrement or as an increment, must be zero taken over z injections. 
This requirement for incorporation of the smooth-running regulating 
arrangement 10 into the entire injection system may be met, for example, 
by means of one of the modifications of the smooth-running regulating 
arrangement shown in FIGS. 3 to 5. 
FIG. 3 shows the block diagram of a part of the smooth-running regulating 
arrangement. In this example, the smooth-running regulating arrangement is 
incorporated into the entire injection system by subtracting the mean 
value of correcting signal S from the output signals of the integrators of 
the regulating units corresponding to the individual cylinders. In this 
example, regulating unit 11 includes an integrator 30, a proportional 
member 31, two subtracting points 32 and 33, and an adding point 34. 
The input signals I1 and Mz applied to regulating unit 11 first are 
combined at subtracting point 32. The output signal of subtracting point 
32 is fed to integrator 30 and proportional member 31. The output signal 
of proportional member 31 is connected to adding point 34 which also has 
the output signal of subtracting point 33 applied to its input. This 
output signal of subtracting point 33 is generated from the output signal 
of the integrator 30 on the one hand and from the mean value of correcting 
signal S on the other hand. The output signal of adding point 34 
represents the correcting quantity S1 which is supplied to synchronizing 
device 18. The output signal of synchronizing device 18 is the correcting 
signal S which is fed to a device 35 for forming a mean value. The output 
signal of device 35 is indicative of the mean value of correcting signal 
S. The mean value device 35 may be a low-pass filter, for example. 
As indicated in FIG. 3, correcting signal S is not only fed back to 
regulating unit 11 but also to regulating units 12 and 13 corresponding to 
the other cylinders. Feeding correcting signal S back to all regulating 
units 11 to 13 of smooth-running regulating arrangement 10 causes the mean 
value of the correcting signal to be equal to zero over z combustions. 
In FIG. 4, the incorporation of the smooth-running regulating arrangement 
into the entire injection system is accomplished by subtracting the mean 
value of the integrators of the regulating units corresponding to the 
individual cylinders from the output signals of these integrators of the 
individual regulating units. 
In this embodiment, regulating unit 11 includes an integrator 40, a 
proportional member 41, two subtracting points 42 and 43 and an adding 
point 44. Input signals I1 and Mz applied to regulating unit 11 are 
combined in subtracting point 42. The output signal of subtracting point 
42 is fed to integrator 40 and proportional member 41. The output signal 
of integrator 40 is then connected to a summing point 45 receiving in 
addition the output signals of the integrators of the regulating units 
corresponding to the other cylinders. The output signal of summing point 
45 is applied to a mean-value device 46 for forming a mean-value signal. 
The output signal of mean-value device 46 is connected to connecting node 
47. Node 47 is connected to all regulating units corresponding to the 
individual cylinders. 
In the regulating unit 11 illustrated in FIG. 4, connecting node 47 is 
connected to subtracting point 43 which has also the output signal of the 
integrator 40 applied to it. Adding point 44 is connected to the output 
signal of subtracting point 43 on the one hand and to the output signal of 
proportional member 41 on the other hand. The output signal of adding 
point 44 represents the correcting quantity S1. By the formation of a mean 
value from all the output signals of the integrators of the regulating 
units corresponding to the individual cylinders and by the subtraction of 
this mean value from these output signals, the requirement for 
incorporation of the smooth-running regulating arrangement into the entire 
injection system is satisfied. 
FIG. 5 shows another embodiment for incorporating the smooth-running 
regulating arrangement into the entire injection system. In this 
embodiment, the mean value of the correcting quantities of the regulating 
units corresponding to the individual cylinders is subtracted from the 
output signal of the integrators of these regulating units. In this 
arrangement, regulating unit 11 includes, for example, an integrator 50, a 
proportional member 51, two subtracting points 52 and 53, and an adding 
point 54. Input signals I1 and Mz applied to regulating unit 11 are 
combined in subtracting point 52. The output signal of subtracting point 
52 is then fed to integrator 50 and proportional member 51. The output 
signal of integrator 50 is connected to subtracting point 53, and the 
output signal of the proportional member 51 is connected to adding point 
54. 
Further, adding point 54 has applied to its input the output signal of 
subtracting point 53. The output signal of adding point 54 represents the 
correcting quantity S1. Correcting quantity S1 is applied to an adding 
point 57 to which further the correcting quantities of the regulating 
units corresponding to the other cylinders are connected. The output 
signal of adding point 57 is applied to a device 56 for forming a mean 
value. The output signal of mean-value device 56 is connected to a 
connecting node 55. 
All the regulating units corresponding to the individual cylinders are 
connected to this node 55 as shown, for example, with reference to 
regulating unit 11 where connecting node 55 is connected to subtracting 
point 53. Because the mean value of the correcting quantities of the 
regulating units corresponding to the individual cylinders is thus fed 
back to the output signals of the integrators of these regulating units, a 
purely dynamic action of the smooth-running regulating arrangement is 
achieved, that is, the correcting signal S is equal to zero over z 
combustions. 
With the smooth-running regulating arrangement described, vibrations of the 
vehicle are to be avoided only in the lower engine speed range, 
particularly at idling. This is accomplished by arranging for the 
smooth-running regulation to become effective only within a specific speed 
range. The transition areas between the range in which the smooth-running 
regulation is active and the speeds at which it is inactive may be 
covered, for example, by means of a control of the smooth-running 
regulating arrangement. In addition, it is also possible to assign in the 
transition areas a factor lying between 0 and 1 to the output signal of 
the smooth-running regulating arrangement, which prevents an abrupt rise 
or fall of the output quantity of the smooth-running regulating 
arrangement. With the controlled smooth-running regulating arrangement in 
operation, its output quantity is further multiplied by a factor which 
lies between 0 and 1 and is dependent on the fuel quantity, in order to 
achieve a smooth increase of the correcting quantity proportional to the 
fuel quantity in the event of a sharp drop in engine speed. 
This is shown in the block diagram of FIG. 6 wherein the blocks which 
correspond to those of FIG. 1 are identified with like reference numerals. 
Block 25 is a muliplier for multiplying the correcting signal S by a 
factor k in the range 0.ltoreq.k .ltoreq.1 depending on the engine speed. 
Block 24 is the threshold for engine speed. 
In the smooth-running regulating arrangement described, the actual-value 
signal, that is, the duration of time between two combustions, was 
determined by means of the segmented wheel. It is also possible to 
generate a speed signal by means of a fast tachometer generator or by 
means of a toothed wheel with a pulse generator and frequency voltage 
converter connected in series therewith. An actual-value signal for the 
smooth-running regulating arrangement can be generated by integration of 
this speed signal from injection to injection or from synchronizing pulse 
to synchronizing pulse. Still another possibility for generation of the 
actual-value signal would be to make an evaluation of the peak value of 
the speed signal between two injection quantities. 
In the smooth-running regulating arrangement described, the combustion time 
points necessary for providing the actual-value signal are determined by 
subdividing the time period between two combustions into two time 
portions. Since it may be desirable to have the transfer of the 
actual-value signal to the memory storage units and/or the transfer of the 
correcting quantities to the fuel-metering apparatus not occur at 
precisely one combustion time point, it is possible to extend the 
smooth-running regulating arrangement described by means of a counter such 
that the counter is reset by a reference signal, for example, by a 
needle-stroke pulse, a pulse indicative of the commencement of injection 
or a pulse indicative of the commencement of combustion, et cetera, and 
drives the two synchronizing devices at specific predeterminable counter 
readings. It is thereby possible to activate the two synchronizing devices 
at any, yet specific, moments of time. The counter may then count up in 
dependence on engine speed and deliver the synchronizing pulses to the two 
synchronizing devices at specific counter readings, or it counts up at a 
fixed frequency and determines the synchronizing time points in dependence 
on engine speed. It is also possible for the counter to be reset on each 
synchronizing pulse and on each reference pulse. 
In the smooth-running regulating arrangement described, the four segments 
of the wheel were evenly spaced over the wheel periphery. By means of 
these segments, the time between two combustions was subdivided into a 
short time duration and a long time duration. For a better distinction 
between the short and long time durations, the wheel segments may be of 
asymmetrical configuration. In the case of the smooth-running regulating 
arrangement described with reference to a four-cylinder internal 
combustion engine, this would mean that only two opposite segments are of 
the same length. This asymmetrical configuration has no influence on the 
determination of the actual-value signal I because the actual-value signal 
I represents the time period between two combustions which covers two 
segments. 
Under normal operating conditions, the segmented wheel subdivides the time 
between two combustions into a short time duration and a long time 
duration. The case may now occur that noise signals of a frequency lower 
than the injection frequency are superimposed upon these time periods. An 
even alternation of short and long time durations is thus no longer 
warranted. The synchronizing devices will then determine whether one time 
duration is longer than the preceding and the following one, thus 
performing a maximum time check. A synchronizing counter which is 
incremented by unity at the end of each time duration is always checked 
when the maximum time check has established a long time duration, for 
example. If the synchronizing is correct, the ends of the long time 
durations will always coincide with odd synchronizing counter readings, 
for example. If, as a result of an error function, the end of a long time 
duration coincides with an even number synchronizing counter reading, the 
synchronization is incorrect. If an incorrect synchronization is detected, 
a check is made to determine whether another incorrect synchronization 
occurs within the next 20 time durations, for example. Only if this is the 
case will the synchronization be changed. 
Error functions may also be detected by a subtraction of the two last time 
durations. In dependence on the result of such a subtraction, a value is 
written into a shift register. A comparison of the values held in the 
shift register with predetermined values permits errors to be detected and 
suitably corrected. The size of the shift register and the predetermined 
values characterizing the error functions have to be determined 
experimentally. 
In the smooth-running regulating arrangement described, the correcting 
signal S was supplied to the fuel-metering apparatus 22 or control 
apparatus 22a in a FIG. 6 which then influences the amount of fuel to be 
injected internal combustion engine, for example. It is to be understood 
that the correcting signal S may also be used to influence other control 
quantities of the internal combustion engine directly or indirectly, as 
for example, exhaust gas recirculation, start of injection, duration of 
injection, air/fuel ratio, ignition point, et cetera by means of control 
apparatus 22a in FIG. 6. 
The apparatus illustrated and described in FIGS. 1 to 5 may be implemented 
using an analog circuit configuration, for example. It is particularly 
advantageous to implement the smooth-running regulating arrangement 
described and, where applicable, further control and/or regulating 
arrangements for fuel metering by means of a suitably programmed 
microprocessor, for example. However, when utilizing such a computer, the 
block diagrams illustrated may no longer be recognizable, having been 
replaced by subroutine structures, time-division multiplex methods, et 
cetera. 
The smooth-running regulating arrangement described is suitable for use in 
internal combustion engines operating pursuant to various different 
operating principles, including internal combustion engines with auto 
ignition, with spark ignition, et cetera. In this arrangement it is 
particularly advantageous that, in dependence on the operating principle 
of the internal combustion engine, the regulating unit corresponding to 
each cylinder of the internal combustion engine influences several control 
quantities of the internal combustion engine directly or indirectly. 
It is understood that the foregoing description is that of the preferred 
embodiments of the invention and that various changes and modifications 
may be made thereto without departing from the spirit and scope of the 
invention as defined in the appended claims.