FR2473626A1 - Microprocessor controlled IC engine regulating system - uses data provided by differential capacitive sensors each having two oscillators to provide as respective pulse trains to microprocessor - Google Patents

Abstract

The system uses a microprocessor supplied with data from sensors monitoring the pressure, operating the engine temp, the oil level and the engine revs. Each sensor comprises a differential capacitive sensor comprising a variable capacitor, responsive to the monitored parameter and a reference capacitor, each capacitor associated with a respective oscillator. Each of the latter is coupled to a pulse former, with a difference stage supplying pulses to the microprocessor corresponding in number to the difference in the number of pulses provided by each pulse former within a given interval. Pref. the difference stage uses two counters respectively receiving the output pulses from the two pulse formers via a gating circuit controlled by the microprocessor and by one of the counters reaching its final count value, a third counter receiving the excess pulses fed to the other counter.

Description

COEIANDE, REGULATION AND MONITORING DEVICE
INTERNAL COMBUSTION IOSEURS
The present invention relates to a device for controlling, regulating and monitoring internal combustion engines, in particular those of motor vehicles, and more particularly to an electronic microprocessor assembly comprising capacitive-type sensors, enabling precise and precise control to be obtained. economic various or pram'tr involved in the operation of said engines such as, angular velocity, pressure and intake flow of the carton, etc..

 Measuring sensors already exist for these quantities, but the object of the present invention is the production of a complete system of sensors comprising easy-to-machine mechanical components and highly integrated electronic components, these advantages permitting a very large-scale manufacture. and the inexpensive equipment of all engines using petroleum fuels, especially those of motor vehicles, from which we obtain either a better yield at a given consumption or a noticeable reduction in consumption at a given average speed.

 In a general manner, the sensors measuring the pressures, the temperatures, the levels and the angular speeds are differential capacitive sensors comprising two capacitors, one of which is of variable capacitance as a function of the quantity to be measured, two pulse oscillators of which said capacitors are part of the oscillating circuit and electronic means to measure the difference in the number of pulses produced by the oscillators during a period of time. This difference in the number of pulses is proportional to the quantity to be measured.

 Thus, whatever the quantity to be measured, the sensor is always a sensor with differential capacitance and the measurement of the quantity is constituted by a number of pulses. These pulses stored in a counter are read by the microcomputer at a repetition frequency defined by the latter.

 The invention will be better understood on reading the following description and examining the corresponding accompanying drawings, in which - FIG. 1 shows the equipment of a motor sensors used for driving and control of its operation; FIG. 2 gives the general diagram of the data processing block; - Figs. 3 and 3A show a diagram of a differential capacitance sensor and a push-pull capacitor; FIG. 4 gives the diagram of the digital counting circuit for a push-pull sensor; FIG. 5 shows the circuit diagram of the operational amplifiers used for transforming the capacitance variations of the sensors into digital pulses; FIG. 6 shows a differential pressure sensor (air / fuel mixture) - FIG. 7 represents a level sensor (oil or fuel); - Figs. 8A and 8B represent temperature sensors (engine or exhaust); - Figs. 9A and 9B represent oil and gas temperature sensors burned; and - Figs. ioA, 103 and it represent a speed sensor, with a part of the corresponding electrical diagram and the timing diagram.

In or on the engine block i (Fig. 1) are located; the sensor it makes it possible to measure the temperature of the oil (or / and the water of the radiator); the sensor 12 identifying the oil level; the sensor 13 giving the position of the butterfly valve of the carburetor 5 (or of the fuel injection valve);
Outside the engine block 1, but nearby, there is (in the subset 2) - the sensor 14 disposed in the exhaust pipe 6 and indicating the temperature of the burnt gases; the sensors 15 and 16 supplying the angular speed of the transmission shaft 8 before and after the gearbox 7 - possibly other sensors, such as 17, providing further data on the engine running - the sensor 18 (compartment 3) giving the pressure in the intake manifold 9 of the air / fuel mixture, thanks to a tubular branch 10.

 At a variable distance from the engine 1, there is in the compartment 4, the sensor 19, dolant the level of the fuel in the tank 20.

 All the sensors 11, 12, 13, 14, 15, 16, 17, 18 and 19 are respectively connected to the electronic circuits 21, 22, 23, 24, 25, 26, 27, 28 and 29 placed in the electronic block 3.

 These circuits 21, 22, 23, 24, 25, 26, 27, 28 and 29 contain a relaxation oscillator of the type which will be described below and a circuit for shaping the oscillations transmitted to the data processing block 60 (FIG. 2) by the threads 31 to 39.

 Block 60 comes back from the control commands - by the wire 41, actuates the member 43 which adjusts the device 5 for admission of fuel (or air / fuel mixture) in the carburetor or the injection valve - by the wire 42, is actuated the member 44 which sets the ignition advance in the ignition device 45.

Block 4 is normally placed in a place not subject to the high temperatures and vibrations of the engine, for example inside the dashboard; the tubing 10, in particular
It is designed to dampen the vibrations caused by gases in the intake pipe.

Fig. 2 represents the electronic assembly comprising
two subsets
block 62 which is placed near or at a distance
conch of block 4, for example also inside the
dashboard
the subassembly 63 which is placed in a visible manner for
the human operator, for example on the dashboard, the
different devices that can be arranged
on this board to make it easier to read.

Block 60 contains
a) a microprocessor 61 of a model commonly existing in
the comnierce and having circuits with high integration b) different interface circuits whose number isd'tresilleurs not limiting. These circuits, microprocessor instructions 61, actuate visual signaling devices such as signal lamps or meter displays, or sound such as ring tones or snoring.

 The following interface circuits are provided - the interface 51 controls the switching on of a general alarm lamp 71 - the interface 52 activates the totaling odometer 72, for example at five digits, of 00000- to 99999 - the interface 53 actuates the partial ktilometric counter 73, for example at three digits, from 000 to 999.

 The indications provided by the displays 72 and 73 come, after processing, from the sensor 16 of FIG. 1.

- The interface 54 actuates a digital revolution counter 74 - the interface 55 actuates a speed indicator 75 in the case where the engine propels a vehicle.

 The values indicated at 74 and 75 come, after treatment, respectively from the sensors 15 and 16 of FIG. 1, given the pulses provided by a clock 69 associated with the microprocessor 61. It will be noted, of course, that the clock 69 allows the display of the time.

the interface 56 displays on the counter 76 the fuel level in connection with the sensor 19; the interface 57 displays on the counter 77 the temperature of the engine in connection with the sensor 11 which is immersed in the crankcase oil; The interface 58 displays on the counter 78 the level of oil in connection with the cap 12; finally, the interface 59 triggers a buzzer 79.

 Of course, it is possible to envisage a larger number of displays or, on the contrary, to restrict them to light.

With this in mind, the same display can be used for the totalised mileage display 72 and the partial mileage display 73 as well as the same display for the display of the engine temperature 77 and the display of the engine level. oil 780
In this case, the displays 73 and 78 are suppressed and the displays 72 and 77 are provided with a switching button, respectively 70 and 70 '.

c) The microprocessor 61 has two outputs 41 and 42, on which are sent instructions to the bodies 43 and 44 (FIG 1) respectively regulating the fuel injection rate and ignition advance (or any other parameter in the case of a diesel engine).

 There are servo controls there according to a program that can be introduced in ROM in the microprocessor 61 based on the characteristics of the engine, its use and the fuel used.

 In FIG. 3, there is shown by way of example the sensor 18 and its associated circuit 28, but the diagram is valid for all the sensors and their associated circuits, with the exception of the sensors and circuits 15-25 and 16 -26 which comprise a variant, described below.

 The sensor 18 consists in practice of two capacitors 1801 and 1802. The capacity of 1801 varies according to the physical quantity to be measured B; that of 1802 is fixed, but this capacitor is subjected to the same environmental constraints as 1801, such as: temperature, vibrations, etc., and by construNoll, it "drifts" in the same way as the capacitor 1801.

 The circuits 1803 and 1804 are two identical relaxation oscillators, close to each other in the same enclosure.

They generate two frequencies F1 and F2, such as: F1 2 F2 when the value of + is zero. A potentiometer 1812 makes it possible to perfect the adjustment of the zero.

 The circuits 1805 and 1806 provide pulse shaping sawtooth oscillations from 1803 and 1804 respectively.

 The circuits 1807 and 1808 are gates allowing or not the passage of the pulses to the precountors 1809 and 1810, which are designed to record only a number n of pulses fixed in advance.

 The counter 1811 records only the number AN of pulses that exceeds n: # N = Nr, where N is the number of pulses provided by the oscillator 1803 while the oscillator 1.304 is in response n (provisionally assumed that N> n, that is to say that the capacity 1801 decreases when the magnitude i increases).

 The beginning of the operating cycle is initiated by a signal from microprocessor 61 (PYg.2) on wire 381, which opens gates 1807 and 1808.

 From this moment, the pulses F1 and F2 enter the counters 1809 and 1810; when 1809 reaches the level n, it overflows and the F1 impulses enter 1811.

 When 1810 reaches the level n, it controls the closing of the doors 1807 and 1808 by the wire 382 and indicates to the micro-compressor 61 (Fig. Ê) that it can raise the indication AN of 1811 by the wire 383.

As soon as 61 has performed this operation, it sends by the wire 381 a reset signal (reset) counters 1809, 1810 and 1811 and opening doors 1807 and 1808; from that moment, the measurement cycle starts again.

The period T of a relaxation circuit formed of a capacitance
C and a resistance R is T = CR and the frequency F =. It has been assumed above that C decreases as a function of 3 in the sensor 1801 and consequently. F = F1 increased; if aucontraire,
C increases and F decreases, the assembly of FIG. 3 remains valid, this time connecting 1801 i 1804 and 1802 to 1803.

 n is chosen in advance and each measurement cycle provides a numerical value of aN.

Suppose that the measuring capacitor 1801 and the reference capacitor 1802 are constituted by parallel planar plates of surface S separated by a dielectric d and constant 6. For the measuring capacitor 1801:

dcoù

Suppose further that the application of t varies d in a substantially linear fashion
d = of + I (.p, whereas for C2 (1802) d = do and

dcoù

et d'après (1)

In the assembly of FIG. 3, let's call the time set by counter 1810 to reach level n
n = F2.t
At the same time, N pulses reach counters 1809 and 1811 and N = F1.t, whence

and after (1)

We see that ON, content of the counter 1811, provides, at a constant coefficient near (which we can equal, thanks to the choice of n, to a power of 10), the numerical value of the quantity
It has been assumed, so far, that F1 increased by 3! increased; in the opposite case, the assembly of FIG. 3 remains valid provided you connect 1801 to 1804 and 1802 to 1803.

 It may be of interest to use a "push-pull" sensor, that is to say having a central electrode and two electrodes located on both sides, so that, when we apply 3E, C1 increases and C2 decreases accordingly; it is always possible to use the assembly of FIG. 3, with the modification of the input connection shown in FIG. 3 where the element 1813 is a push-pull sensor.

 However, a more advantageous scheme, in the case of the pushpull, is that of FIG. 4.

The output of the oscillators 1803 and 1804 is sent to a ring modulator 1814 which supplies at its output modulation products at the main frequencies = F = T1 + F2 aF = Fi - F2
The mounting of the block 28 'differs from that of the block 28 only by the addition of the modulator 1814 and the circuits 1815 and 1816 which consist of identical operational amplifiers, each comprising a feedback circuit constituted by a filter RC passes -band, granted on CF for 1815 and on F for 1816; the shaping circuits 1805 and 1806 are then attacked as before.

 Under these conditions, there are n pulses of zF and N pulses of # F and the counter 1811 records tN pulses.

c'est-à-dire que la formule 2 devient : O = 2 k aN (3)
la sensibilité est doublée par rapport au condensateur simple. In the case of the push-pull, we find that

that is, formula 2 becomes: O = 2 k aN (3)
the sensitivity is doubled compared to the simple capacitor.

 Fig. 5 is a diagram of a relaxation oscillator used for both the measuring oscillator 3 and the reference oscillator 74 of FIG. 3.

 The sensor (70 or 72, Fig. 3) is connected to input 1817 of circuit 1803 (Fig. 5); an input terminal is connected to the input 1818 (+) of the operational amplifier 1800 and the other terminal to ground.

At the input 1818 of 1800 is also connected the resistor 1819 which, with the adjustable resistor 1812 (see Fig. 3), constitutes the load resistor R of 1801; R, associated with the capacitance C, of this sensor, determines the value of the frequency

 The output 1819 of the amplifier 1800 is connected to the input of the shaping circuit 1805 of FIG. 3.

 Note that the wire 1821 has a ground shield which extends to the sensor 1801.

 The summed value of the resistors 1812 and 1819 is determined according to the capacitance of the sensor so that the minimum value of F1 is high enough so that the quantization error on AN is negligible, given the required accuracy, of the order of 10kHz for example.

 The resistor circuit 1822 adjustable capacitor 1823 is derived from the load resistor 1812-1819 and allows, by a suitable choice of components, to give the response curve of the block 1803 the most favorable form for the measurement of, according to the nature of the physical phenomenon; to this is added the fact that the microprocessor 61 can itself introduce corrections in the shape of this curve.

The pressure sensor 18 is shown in section on the
Fig. 6; it is the push-pull capacitor 1813 shown diagrammatically in FIG. 3A.

 It is composed of - a metal case of revolution 1850 on which is screwed the piece 1851 extended to the intake pipe 9 by the tubing 1852 - a bellows diaphragm 1853 Durinval (metal having very low variation in temperature of size and Young's modulus), placed (at rest) equidistant from the metal plates 1854 and 1855, the thickness of the air gap between 1853 and 1854 or 1855 being 0.5 at 1 mm at rest and not falling below 0.2 mm for the maximum differential pressure.

 The equalization of the internal pressures on each side of 1853 is through orifices such as 1856 and 1857 and the 1858+ hole of 3 isolated outputs 1859, 1860, 1861, electrically connected by a 3-conductor cable to block 28 (FIG. 3A).

 The blades 1853, 1854 and 1855 cont connected to these three outlets, themselves being insulated from the housing 1850 by 4 insulating washers 1862, 1863, 1864 and 1865, which also act as wedges.

 The introduction of the different parts of the sensor 18 is obtained by clamping the part 1 851 on the housing 1 850 with sufficient pressure to obtain a precise setting.

beech
The sensor of FIG. 6 can also be used as a single-effect sensor, as shown in 1801 and 1802 in FIG. 1; it suffices to interchange the electrodes 1853 and 1854 with the assembly; 1853 and 1854 are then connected to the entrance of 1803 and 1855-1854
to 804 (Fig. 3).

 A level sensor operable to measure the level of either oil or gasoline (12 or 19, Fig. 1) is shown in Fig. 7.

 The sensor 12 (or 25) consists of a cylindrical body of revolution 1200 screwed into the casing 1, the seal being provided by the seal 1201.

 Inside 1200 is on a length depending on the dimensions of the housing (or tank) a rod 1202 extended by a tube 1203; the diameter of 1202 is small compared to the inner diameter of 1200, but the diameter of 1203 is close to the latter.

 1202 is positioned and isolated by the plug 1204; similarly, 1203 is insulated by 1205, pierced with an orifice 1206 allowing the passage of the oil (or fuel) which, through the orifices such as 1207, spreads outside 1203 to reach its level 1208.

 The number of 1202 and 1203 is determined so that 1203 is immersed in the oil (or fuel) between the maximum levels 1209 and the minimum 1208.

 Since the dielectric constant of the oil (or fuel) is substantially higher than that of air, approximately 2 to 3 times, and the capacity 1200-1202 being low, it can be seen that the residual capacity is low and that the capacity variation is a linear function of level 1208.

 The accuracy with which this level must be known to be relatively low (of the order of 1,;), the reference capacitor is constituted by a simple commercial component contained in block 22 or 29.

avec Ci IcI on trouve :

In this case, the measurement frequency

with Ci IcI we find:

et i = aAN + b (fonction linéaire)
Les Figs. 8a et 8b représentent le capteur de position angulaire 13 qui comprend, à l'intérieur du boftier métallique 1300, des lames fixes isolées 1301 constituant une électrode du condensateur, fixées au moyen des entretoises isolantes 1302 et des lames mobiles isolées 1303 portées par l?axe 1304 qui est aussi l'axe du papillon du carburateur (ou de la valve d'injection) 5 (Fig. 1), Les lames 1303 ont une forme de quadrant circulaire (dans le cas où leur course, limitée au repos par la butée 1305, est de 90, mais il est évident que leur angle d'ouverture pourrait entre porté à 180 si nécessaire).In this case, F1 is sent to the circuit 1804 of FIG. 3 and F2 on the 1803 circuit; we then

and i = aAN + b (linear function)
Figs. 8a and 8b show the angular position sensor 13 which comprises, inside the metal housing 1300, insulated fixed blades 1301 constituting an electrode of the capacitor, fixed by means of the insulating spacers 1302 and isolated movable blades 1303 carried by the 1304 which is also the axis of the throttle valve of the carburettor (or the injection valve) 5 (FIG 1), The blades 1303 have a circular quadrant shape (in the case where their stroke, limited to rest by the stop 1305, is 90, but it is obvious that their opening angle could be increased to 180 if necessary).

The capacity variation, when the axis 1304 rotates, is proportional to the angle of rotation, that is to say that a = a + b
The number of blades 1301 and 1303 and their spacing are determined according to the maximum capacity to obtain; a value of the order of 200 pF is sufficient.

 A recess 1306 of the fixed blades 1301 is provided to decrease the residual capacity.

 On the section along the sectional plane 8A-8B, the two electrical outputs 1307, isolated at 1309, and 1308 connected to the metal housing, that is to say to the general earth, would be used; these two outputs are connected, as indicated above, to block 1804 (Fig. 3).

 In FIG. 9A, there is shown the engine oil temperature sensor 11, of the same design as the sensor 12 of FIG. 7, but with this difference that it is screwed to the lower part of the housing and that its length is determined so that it bathes in the oil, even for the minimum level 1109.

 In addition, the dielectric between the body 1100 and the tube 1103 is constituted by an insulator 1102, for example a ceramic, optionally doped with a rare or alkaline metal, whose dielectric constant varies significantly with the temperature.

 The metal of 1103 has a higher coefficient of linear expansion than that of the body 1100; the latter is for example made of steel and 1103 of copper or aluminum alloy. In this way, the insulating sleeve 1102 works consistently with compression, regardless of the temperature.

A sensor such as 11 may also be inserted into the exhaust pipe 6 of the flue gases, but to avoid rapid deterioration of the sensitive part of this sensor, a preferred embodiment in this case is that of the sensor 14 of the
Fig. 9B.

 The sensor 14 consists of three contiguous sleeves 1400, 1401 and 1402, themselves -mbmes force-fitted on the pipe 6 through which the hot gases.

 The sleeve 1402 is constituted, like 1102, by a ceramic with sensitive variation of the dielectric constant as a function of the temperature and resistant to temperatures normally between 300in and 800C.

 The inner sleeve 1401 is made (like 1103) of a less expandable metal than that of the outer sleeve 1400 (like 1100).

 The sleeves 1402 and 1400 are electrically connected to the input of the block 24 of FIG.

 A capacitive speed sensor is shown in Figs. 10A and 10B in longitudinal section and in partial cross-section. 8 or 8t is the front transmission shaft (sensor 15) or rear shaft (sensor 16) of the gearbox 7 (Fig. 1); on this shaft is fixed a metal sleeve 1501 supporting the capacitor blades 1502 (which are therefore capacitively to the general mass).

 A housing 1500, fixed to a bearing 1503 supporting the shaft 8 or 8 'and of circular section, supports the blades 1504 by means of the insulating washers 1505 also serving as wedges for mounting; these blades are electrically connected together and at the isolated output 1506 which, together with the housing ground, are connected by cable to the circuit 25 or 26 of FIG. 1.

The blades 1502 or 1504 have the shape indicated on the transverse cut-out, a form which, moreover, has nothing critical; when the blades 1502 turn and approach the fixed blades 1504, the capacity between them, practically zero in the position shown, increases, passes through a maximum when the axes coincide, then decreases to cancel
The frequency F1 produced by the oscillator 25 or 26 at the moment when the blade 1502 approaches the blade 04 is first raised, then goes through a minimum to increase again, as indicated by the curve 1507.

 This oscillation is rectified at the output of the block 1803 by the diode 1508 outputting on the resistor 1509, amplified at 1510 and filtered by means of the feedback circuit 1511, 1512, 1513, acting as a low-pass filter for the frequencies. - equal to or greater than the minimum of 10 kHz.

 At the output of 1510, the current form indicated by curve 1514 is obtained; this current is applied to the shaping circuit 1805 which provides two rectangular pulses, one at the rise, the other at the descent of the current 1514.

 By way of example, four blades 1502 have been represented; suppose that at idle the engine runs at 600 rpm and at a maximum speed of 6000 rpm, ie 10 and 100 rpm; the described installation makes it possible to obtain between 4x2x10 = 80 and 4x2x100 = 800 pulses / second (to compare with 10 kHz above).

 The frequency F2 is then set to provide a number of pulses / second is less than 80 Hz, or greater than 800 Hz. The value AN supplied by the counter 1811 will be proportional to the angular velocity of the shaft 8 or 8l.

 It is obvious that the pulse frequency 1515 can be increased by increasing the number of blades 1502 and 1504 in the same plane, for example 16 instead of 4 as shown.

 One can also play on the thickness of the blades of air between 1502 and 1504 or their transversal number (here 4 x 5 blades 1502 and 4 X 4 1504 pay); it suffices to reach a maximum capacity of the order of a few hundred picofarads to obtain satisfactory results.

Claims (7)

Patent claims  1 - Internal combustion engine control system comprising a microprocessor, data sensors including at least one pressure sensor, a temperature sensor, a liquid level sensor and an angular speed sensor, and means for regulating motor control and regulation devices according to the current values of said data, said system being characterized in that the sensor cells are all differential capacitive sensors composed of a variable capacitor as a function of the detected data and a reference capacitor, two oscillators associated with said capacitors and having these capacitors respectively in their oscillating circuit pulse shaping circuits connected to said oscillators, means for forming the difference between the numbers of pulses produced by the shaping circuits for a time predetermined and ways to apply impulsio ns in number equal to said difference to said microprocessor as a measure of the detected data.  2 - Internal combustion engine control system according to claim 1, characterized in that the means for forming the difference between the numbers of pulses generated by the shaping circuits for a predetermined time comprises a first counter and a second counter respectively receiving the pulses produced by the two shaping circuits, the first counter overflowing from a predetermined value, the doors controlling the access of the pulses in said first and second counters, said doors being opened by the microprocessor and closed by the second counter when it reaches said predetermined value, and a third counter connected to the first counter and receiving from it the pulses it has itself received and whose number exceeds the predetermined value.  3 - Internal combustion engine control system according to claim 1, characterized in that, between the oscillators and the shaping circuits, it comprises a ring modulator receiving the signals of the two oscillators, filters separating the signals whose frequency is the frequency output of the two oscillators, signals whose frequency is the difference of the frequencies of the two oscillators, the shaping circuits being respectively connected to said filters.  4 - control system of internal combustion engines according to claim 1, characterized in that the capacitive temperature sensor is a coaxial capacitor whose armatures are separated by a dielectric material whose dielectric constant varies with temperature.  5 - Internal combustion engine control system according to claim 4, characterized in that the outer armature of the coaxial capacitor has a lower coefficient of expansion than the inner frame.  6 - Internal combustion engine control system according to claim 1, characterized in that the liquid level capacitive sensor is a coaxial capacitor whose armatures are separated by air, said capacitor having a communiction with the liquid so that it enters the interval between frames.  7 - Internal combustion engine control system according to claim 1, characterized in that the solar capacitive speed sensor comprises a stator with fixed blades and a rotor with movable blade wedged on the shaft of which one wants measuring the speed, means for detecting the output signal of the rotor and means for differentiating said detected signal so as to obtain pulses coinciding with the beginning and the end of the detected signals.