Device for controlling the ignition and fuel injection of an internal combustion engine

A device for controlling the ignition and the fuel injection of an internal combustion engine, including a pressure sensor, a position sensor associated with a target fixedly mounted in rotation with the crankshaft, a first computer of the programmed microcomputer type in which are stored values of the angle of advance and the injection time addressable as a function of the engine speed and pressure parameters, and a second computer which, from the output signal of the position sensor applies to the first computer a synchronization signal assuring the marking of each top dead center and/or each bottom dead center, the first computer receiving the output signal from the pressure sensor and computing, as a function of the parameters and under the control of the synchronization signal, the injection time and the angle of ignition advance, the value of the latter being applied by the first computer from the second computer which computes the conduction angle of the ignition coil and controls the conduction of the coil as a function of the computed angles of conduction and ignition advance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a device for controlling the ignition and fuel 
injection of an internal combustion engine, of the type having a digital 
computer system programmed to compute the ignition advance and the 
injection time as a function of the speed and the load of the engine. 
2. Description of the Prior Art 
In any device of the above-noted type, it is necessary to measure the 
engine speed and to know with good precision the instantaneous angular 
position of the crankshaft so as to trigger the ignition at the computed 
angle as a function of the measured speed and load. 
For this purpose, it is known how to use a target fixed in rotation with 
the crankshaft and exhibiting at its periphery one or more irregularities 
passing before a sensor that supplies a synchronization signal Sy at each 
passage of a piston by a predetermined position such as a top dead center 
(TDC) and/or by a bottom dead center (BDC). This synchronization signal 
makes it possible, between two consecutive TDCs or BDCs, to measure the 
speed with a precision suitable for computation of the angle of advance 
and the injection time and to trigger the start of the injection at the 
desired moment, generally at the top dead center, but it is not suitable 
for triggering the ignition which, for a given stroke, is offset by 
several dozen degrees in relation to the preceding TDC or BDC. 
One solution which consists in performing an electronic interpolation of 
the synchronization signal is not satisfactory because, in case of sharp 
acceleration or deceleration of the engine, the electronically restored 
angular position does not coincide with the true angular position of the 
crankshaft. 
Another solution consists in using a second target also fired in rotation 
with the first and provided at its periphery with several dozen regularly 
spaced teeth and hollows which pass before a second sensor. Further, since 
the angular resolution necessary for triggering the ignition would lead to 
a number of teeth and hollows incompatible with a large series production, 
an electronic interpolation of the signal coming from the second sensor is 
preferably performed. The synchronization of the interpolation signal is 
done at each detection of a new tooth and/or a new hollow, which makes it 
possible to avoid any significant error in case of sharp acceleration or 
deceleration of the engine. However, this second solution has the drawback 
of being costly on the industrial level because it requires the use of two 
sensors and two targets which, in addition, must be perfectly angularly 
adjusted in relation to one another. 
U.S. Pat. No. 4,321,580 describes a process which makes it possible to 
solve this problem by measuring the speed and marking the angular position 
of the crankshaft by means of a single sensor in front of which passes a 
target equipped at its periphery with a series of teeth and hollows and 
from which at least one tooth has been eliminated to constitute an 
absolute reference. U.S. Pat. No. 4,367,710 describes a specific ignition 
computer that uses this process and makes its possible to obtain the 
synchronization signal Sy, an image tooth signal Sd of the teeth of the 
target and an interpolation signal or frequency speed signal V n times 
greater than Sd. From these signals, the computer computes the angle of 
ignition advance, the conduction time of the coil and consequently 
controls the coil. This computer can consist of the integrated circuit SN 
96 528 of the Texas Instruments Company. 
Since it involves a specific circuit, this computer is not programmable and 
therefore is not suitable to assure the additional function of controlling 
the fuel injection. 
On the other hand, the processing of the signal, if it is desired to have 
sufficient dynamics to measure the rotation speed and an accurate marking 
of the TDC and/or BDC, the computation of the conduction angles of the 
coil and the angles of ignition advance, and the computation of the 
injection time would make it necessary to use a priori a fast and powerful 
and consequently costly, microprocessor. 
Another solution described in the article titled "Engine Controls Become 
More Cost Effective" in the magazine Automotive Engineering, volume 89, 
No. 8, August 1981, consists in using two single chip microprocessors 
working in parallel, one for the ignition, the other for the injection, 
from a certain number of parameters some of which are common. A first 
drawback of this solution resides in the fact that the marking of the 
instantaneous angular position of the crankshaft is assured by an 
electronic interpolation of the synchronization signal that produces a 
pulse theoretically every 0.35.degree. of rotation. Unfortunately, as 
previously shown, this restored angular marking is proved erroneous when 
the crankshaft is subjected to sharp accelerations or decelerations, as is 
the case at the low speeds of slowing down or at starting. Moreover, this 
solution with two microprocessors nevertheless remains costly because for 
a very large series production the cost of even a single chip 
microprocessor is greater than a microprocessor with a specific integrated 
circuit. 
SUMMARY OF THE INVENTION 
Knowing that the production rates of electronic injection systems are still 
currently markedly lower than those of electronic ignitions, an object of 
this invention is to provide a novel device for controlling the ignition 
and injection for an internal combustion engine which combines the 
advantages of the low cost of specific integrated circuits for the very 
large series and of the single chip microprocessors for smaller series, 
and which assures the use of the process described in the U.S. Pat. No. 
4,321,580 for measuring the speed and making the precise instantaneous 
angular position of the crankshaft by means of a single sensor. 
For this purpose, the invention has as its object a device for controlling 
the ignition and fuel injection of an internal combustion engine, 
including a target fixed in rotation with the crankshaft and associated 
with an angular position sensor, at least an ignition coil, at least a 
sensor for the pressure in the intake manifold of the engine, at least an 
injector and a computation system in which are stored the values of the 
angle of advance and injection time addressable as a function of the 
parameters for the engine speed and the pressure in the intake manifold 
and which, from the output signal of the position sensor, processes a 
synchronization signal identifying the passage of each piston by a 
predetermined position such as a top dead center and/or by a bottom dead 
center and computes the engine speed, the computation system including a 
first programmed microcomputer connected to the pressure sensor and 
controlling the injector and a second microcomputer connected to the 
position sensor and controlling the ignition coil, characterized in that, 
on the one hand, as known in the art, a single position sensor is 
associated with the target equipped at its periphery with a series of 
teeth and hollows at least one tooth of which has been eliminated to 
constitute an absolute reference and the second microcomputer is a 
specific ignition computer which processes the synchronization signal, an 
image signal of the teeth of the target and a frequency speed signal n 
times greater than that of the tooth signal from the output signal of the 
position sensor and which exhibits read only memories for advance 
correction factors and full load advance factors and for additional 
advance correction inputs, and wherein, on the other hand, the read only 
memories of the second computer contain a zero value while the values of 
the angle of advance and the injection time are all stored in the first 
programmed microcomputer which receives the synchronization signal from 
the second microcomputer, computes the engine speed and applies the value 
of the angle of advance to the additional inputs of the second 
microcomputer which, as a function of the signals processed from the 
output signal of the sensor, computes the conduction angle of the coil and 
controls the conduction of this coil according to the computed angles of 
conduction and ignition advance. 
As a result of this arrangement, the specific ignition computer works as a 
slave, without undergoing any modification other than that of a particular 
programming for the law of advance which, for a "purely ignition" 
application, depends in any case on the engine under consideration, while 
freeing the microcomputer from routine tasks. This arrangement makes it 
possible to overcome one of the main handicaps of the specific integrated 
circuits which is their unsuitability for applications other than those 
for which they were originally designed, and, from the cost viewpoint, 
makes the optimum trade-off mentioned above by the association of a 
specific circuit manufactured at a very high rate for ignition alone and 
ignition combined with injection, and of a microprocessor concerned only 
with the second of these applications representing considerable smaller 
rates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to the drawing, the computation system includes essentially 
a first computer 1 consisting of a programmed microprocessor of the 
current type (single chip) such as, for example, the microprocessor MC 
6801, and a second computer 2 which will be described in more detail 
below. 
Microprocessor 1 receives from a sensor 3 the data on the pressure in the 
intake manifold converted into digital form by an analog to digital 
converter 4, and from computer 2 a synchronization signal Sy from which it 
computes the engine speed and which makes it possible to identify the 
passage of each cylinder at predetermined TDC. Microprocessor 1 contains 
in storage the values of the angle of advance and injection time 
addressable as a function of the speed and pressure parameters and 
computes, under the control of the synchronization signal Sy, the 
injection time for the control of one or more injectors 6 and of an 
injection pump 7 by power circuits 8 and 9, respectively. The 
microprocessor sends by its outputs Po, P.sub.1 and P.sub.2 and P.sub.3 
the computed value of the angle of ignition advance to computer 2. 
Computer 2 has a first section 2a and a second section 2b. The first 
section 2a consists of a digital processing block 13 which receives as an 
input, after forming by the analog circuit 5, consisting for example of 
the circuit SN 96 532 of the Texas Instruments Company, the signal taken 
by a position sensor 11 that detects the passage of the teeth which are 
provided at the periphery of a target 10 fastened on the crankshaft 12 of 
the internal combustion engine and that turns in synchronism with the 
crankshaft 12. From the output signal S.sub.d of the analog circuit 5, 
block 13 produces the synchronization signal Sy and a frequency speed 
signal V n times greater than Sd. This block 13 and the manner in which 
the signals Sy and nSd are processed are described in U.S. Pat. No. 
4,321,580 which can be referred to. 
The section 2b has a computation block 19 which receives the 
synchronization signal Sy on an input 16 and speed signal V on a second 
input 17. 
The essential parts of computation block 19 are the following: a sequencer 
30; a stage for measuring speed 31; a read only memory 32; a pressure 
measurement stage 33; a safety stage 34 for guarding against any 
operational trouble of the computation block 19; a corrections stage 35 
connected by three input conductors 38a, 38b, 38c at outputs Po, P1 and P2 
respectively of microprocessor 1 and a stage 36 for computing the angle of 
ignition advance receiving data from output P3 of microprocessor 1 by an 
input 41 of series pulses. This computation block has been described in 
U.S. Pat. Nos. 4,127,091 and 4,239,024. 
Computation block 19 delivers by its respective outputs 21 and 22 two 
binary numbers which correspond respectively to the conduction angle of 
coil 27 expressed as the number of teeth of the target 10 on its output 21 
and to the angle of ignition advance expressed as the number of teeth of 
target 10 and as the number of subdivisions between two teeth of said 
target on its output 22. These two binary numbers arrive by the conductors 
21 and 22 as an input on a block 20 for generating the control signal of 
the coil 27. Block 20 also receives as inputs thereto three signals by 
conductors 14, 15 and 18 which are respectively the sensor signal in Sd 
form, the speed signal V and the synchronization signal Sy. Block 20 for 
generating the control signal of the coil supplies on its output 23 a 
low-power signal which is sent to a power amplifier stage 24 whose output 
28 is connected to ignition coil 27. Coil 27 has a primary winding 26 and 
a secondary winding 29 connected by one of its ends to the central part of 
a distributor 42. Mobile arm 43 turns around the central part of 
distributor 42 and successively connects, during its rotation, the 
secondary 29 of the ignition coil 27 with the spark plugs of the various 
cylinders of the engine to cause the explosion and the combustion of the 
fuel mixture contained in the cylinders. This last group, including block 
20 for generating the control signal of coil 27 and power amplifier stage 
24, has been described in U.S. Pat. No. 4,367,710. 
Computer 2 which has just been briefly described and whose detailed 
operation is explained in above-noted patents can consist of an integrated 
circuit such as the circuit SN 96 528 of the Texas Instruments Company. 
This circuit is supposed to compute independently the conduction angle of 
coil 27 and the angle of ignition advance. In the device according to the 
invention, it fulfills only the first of these functions, the second being 
assured by microprocessor 1. For this purpose, the additional inputs 38a, 
38b, 38c normally used to receive additional random corrections coming 
from various sensors and input 41 for correction of advance as a function 
of the pinging (inputs which are described in the French patent 
application No. 2,485,641) are, in this device, intended to receive 
constant corrections coming from microprocessor 1 and being used to 
generate the law of ignition. Moreover, contrary to the explanations given 
in French Pat. No. 2,485,641, the read only memories for the factors of 
advance correction and full load advance contain all the value 0.degree. 
since the corrections sent by microprocessor 1 to the additional inputs 
38a, 38b, 38c and 41 correspond to the computed value of the angle of 
ignition advance. 
Finally, computation block 19 receives no "pressure" data contrary to what 
is indicated in French patent application No. 2,485,641 since it is 
microprocessor 1 which directly receives this data from the analog to 
digital converter 4, which makes it possible to use a single pressure 
sensor 3 to compute the angle of ignition advance and the injection time. 
Target 10 includes, for example, 44 regularly spaced teeth of which two 
times two teeth have been removed at 90.degree. from each top dead center 
or bottom dead center in the case of a four cylinder engine. Signal Sd 
sent from sensor 11 and formed by analog circuit 5 is applied to computer 
2. Block 13 processes this signal Sd (not to be confused with the signal 
Sd of U.S. Pat. No. 4,321,580 which, itself, designates the restored tooth 
signal, i.e., the sensor signal formed and in which further the missing 
teeth are electronically restored) so as to produce the signal Sy which 
identifies the passage of the pistons at a top dead center. Moreover, the 
microprocessor which receives this signal Sy can then compute the engine 
speed and, from the pressure data coming from comverter 4, the angle of 
ignition advance and the injection time, in synchronism with the engine 
strokes, according to appropriate algorithms which will not be described, 
these algorithms being well known to specialists of the art. 
As a result of the synchronization signal Sy and its inner clock, 
microprocessor 1 controls the beginning of the injection at a given moment 
after the top dead center and for the computed time. 
Moreover, microprocessor 1 indicates at block 19 what angle of advance it 
must supply to block 19. By programming, for example, flywheel values 
8.degree., 16.degree. and 32.degree. for the additional corrections on the 
inputs 38a, 38b and 38c, microprocessor 1 can indicate all the advances 
between 0.degree. and 56.degree. as engine flywheel by a step of 
80.degree.. The maximum value of 56.degree. is generally largely 
sufficient for all internal combustion engines. Output P3 of 
microprocessor 1 is used to refine the generation of the law of advance 
and to obtain a precision of 1.degree. of the angle of advance. For this 
purpose, output P3 of microprocessor 1 is connected to input 41 of 
computation block 19, including another input 40, which controls the sign 
of the correction applied at input 41, and is prepositioned so that this 
sign is negative. Microprocessor 1, therefore, has to send in parallel 
only a signal "0" or "1" on the three inputs 38a, 38b and 38c to make an 
approximation of the value of advance to be generated by a step of 
8.degree., a value which is decremented one degree at a time by sending to 
input 41 a number of pulses between 0 and 7 to correct the "approximated" 
value and to indicate at block 19, with a resolution of 1.degree. the 
value of advance to be taken into account. 
There can be generated, for example, a flywheel angle of advance of 
22.degree. by controlling two of the inputs 38a, 38b, 38c for generating 
"corrections" of 8.degree. and 16.degree., and the microprocessor will 
only have to send two series pulses to 41 so that the computation block 19 
effectively delivers this flywheel value of 22.degree. with a conduction 
angle that computer 2 will have determined, indicated in U.S. Pat. No. 
4,367,710 or French Pat. No. 8023502, from the measurement of the engine 
speed that it will have performed parallel to microprocessor 1. The time 
lost by microprocessor 1 in sending the necessary data to computer 2 is 
therefore very short. 
The computation system of the device for control and ignition according to 
the invention is, therefore, particularly inexpensive since it requires 
only a single pressure sensor and since it associates a computer designed 
initially to generate independently the law of ignition and produced in 
large series at a low cost with a low-power microprocessor of the current 
type. 
The use of a low-power microprocessor is made possible because the 
low-power microprocessor is freed from processing the synchronization 
signal and from functions relating to the control of the ignition coil, 
namely computation of the conduction angle, regulation of the current and 
varying of dwell. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.