JPS6143534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for measuring the amount of air taken in an internal combustion engine, particularly for vehicles equipped with an electronically controlled fuel injection system having an inlet throttle valve for each cylinder. METHODS AND APPARATUS.

It is a requirement for all electronic fuel injection systems for internal combustion engines to be able to measure the amount of air taken into the engine under different operating conditions.

In practice, control of the engine depends on proper control of the air-fuel mixture throttling, the air-fuel ratio generally varying around the ratio of chemical equivalents depending on the operating regime and load. Therefore, it is necessary to know the amount of air being drawn in so that under any operating conditions, the amount of fuel that can achieve the required air-fuel mixture ratio can be supplied.

The amount of air inhaled can be measured by direct or indirect methods. For direct measurement, a volume flow meter or a mass flow meter is inserted into the intake conduit. In the case of indirect measurement, the amount of intake air is determined by specific parameters based on experimental results under bench brake test driving conditions. In the case of indirect measurements, the fundamental parameters that indicate the specific operating conditions are the engine speed and the absolute pressure in the intake manifold or the angle of the opening of the throttle valve, the latter two values being correlated with each other. There is a relationship.

In fuel injectors with a single throttle valve, the average pressure in the intake manifold is measured. Although the device is virtually unresponsive to atmospheric pressure fluctuations, as this inevitably results in a filled space chamber forming in the intake manifold between the inlet valve and the throttle valve, the device Applied to an injector with a single throttle valve per unit, variations in atmospheric pressure will result in variations in the measured average pressure, as explained below.

In engines of the above-mentioned type with a throttle valve per cylinder, it is customary to measure the pressure in at least one intake line downstream of the throttle valve and to determine an average value from these values. However, this method detects pressures that are dependent on atmospheric pressure, as explained below.

The purpose of the present invention is to indirectly measure the flow rate of intake air.
In other words, using a device that measures without using a flow meter,
To provide a method for measuring the amount of air taken into an oil cycle four-stroke internal combustion engine equipped with a fuel injection system having one throttle valve per cylinder and four cylinders, and making the measurement unaffected by fluctuations in atmospheric pressure. That's true. Another object of the invention is to provide a device for carrying out the above-described method, which can be manufactured easily at low cost and which exhibits the best precision for any type of application.

According to one aspect of the invention, there is provided a method for measuring the flow rate of air intake into a four-cylinder fuel-injected, oil-cycle engine having one throttle valve per cylinder, wherein the pressure of the intake air is small. Both are measured by a pressure detector located between the inlet valve and the throttle valve of one cylinder, and the resulting pressure signal is
Samples are taken within a precise range of angular position of the engine's crankshaft.

According to another aspect, the invention provides an acoustic wheel driven by an engine, a dead center position detector for detecting the dead center position of a member rotating at the speed of the engine, and a dead center position detector for detecting the dead center position of a member rotating at half the speed of the engine. an associated tuned detector; a pressure detector for sensing pressure in the intake manifold short pipe between an associated inlet valve and a throttle valve of at least one cylinder; and an amplifier for the pressure signal from the pressure detector. and a switch device having a second input terminal coupled to the output terminal of the amplifier;
and a first switch device having a second input terminal; a first switch device having a first input terminal coupled to the output terminal of the first switch device and a second input terminal coupled to the dead center position detector. a gate device;
a second switch device having a first input terminal and a second input terminal coupled to the output terminal of the first gate device; a first input terminal coupled to the output terminal of the second switch device; and a first input terminal coupled to the output terminal of the second switch device; a second gating device having a second input terminal to which a pulse signal from the pick-up of the wheel is applied; and a counter having a second input terminal coupled to the first input terminal and an output terminal of the second gating device; A shaping device for shaping the pulse output signal of the pickup, the output signal of the dead center position detector, and the tuning signal of the tuning detector applied to the first input of the first switch device and the first input of the counter. an angular position preselector, a first input terminal coupled to the output terminal of the counter, a second input terminal coupled to the output terminal of the angular position preselector, and a first input terminal of the first switching device. a comparator having an output terminal coupled to both an input terminal and a first input terminal of the switching device; and an input terminal coupled to the output terminal of the switching device. a memory for providing an output signal indicative of intake airflow within a range.

The invention will be described below with reference to the accompanying drawings relating to a four-stroke, four-cylinder engine.

In FIG. 3, reference numeral 2 designates the intake manifold of an otto-cycle four-cylinder internal combustion engine having a single throttle valve, the manifold having four throttle valves upstream of the inlet valves (not shown) for each of the four cylinders of the engine. It has a short tube 4. The intake manifold 2 has a single throttle valve 6 which controls the supply of air by means of a chamber 8 located upstream of the inlet valve.

FIG. 4 shows an intake manifold 2 of an engine to which the present invention is applied. The manifold 2 has four throttle valves 6 connected to and operated by an accelerator pedal (not shown) of the vehicle, each throttle valve 6 leading to a respective inlet valve of the engine (not shown). located within each short tube of the guiding manifold. A pressure transducer for measuring the air flow rate according to the invention is located in one of the short tubes 4.

Reference numeral 2 in FIG. 7 indicates a throttle valve 6 that controls the supply of air to the four cylinders of the engine connected to it.
1 shows a fuel-injected four-cylinder internal combustion engine with an intake manifold having four short pipes 4 with respective throttle valves 6; Pressure detector or pressure sensing transducer 8
is located in one of the cylinders between the respective throttle valve 6 and the cylinder's associated inlet valve (not shown). A wheel 10 with teeth 12 is driven by the engine 2 and cooperates with a first pickup or tuning detector 14 . An acoustic wheel 16 having a pair of diametrically opposed teeth 18 cooperates with a second pick-up or dead center position detector 20 in front thereof, and a third pick-up 22 with teeth 23 on the periphery of the wheel 16. However, the wheel 16 is driven at the rotational speed of the engine, for example by being coupled to the engine's crankshaft.

The electric signals provided by the pick-ups 14, 20, 22 are transmitted to the respective molding circuits or molding devices 24, 26, 2.
Sent to 8. The output of the circuit 24 is a configuration input (first input) 30 and a reconfiguration input (second input) 68.
is applied to the setting input 30 of a bistable multi-oscillator or first switch device 32 having a

The output of the vibrator 32 is sent to a first input 34 of an AND gate or first gating device 36,
A second input 38 of 6 receives the output of shaping circuit 26 . The output of the AND gate 36 is the setting input (first
input) 40 and a resetting input (second input) 70 to the setting input 40 of a bistable multi-oscillator or second switch device 41, the output of the vibrator 41 being fed to the AND gate or second gate device. 44 and a second input 4 of gate 44 .
6 receives the output of the shaping circuit 26. gate 44
The output of the counter 50 is sent to the first input 48 and the second input 52 of the counter 50 is sent to the shaping circuit 2.
Receive the output of 4.

The counter 50 is coupled to a first input 53 of a comparison circuit or comparator 54 and a second input 56 of the circuit 54.
is connected to the output of the angular position preselector 58. The pressure detector 8 is coupled to an amplifier 60, the output of which is coupled to a first input 62 of an electronic switching device 64, and a second input 66 of the device 64.
receives the output of the comparison circuit 54, which output is connected to the resetting input 68, of the bistable multi-oscillator 32, 41.
Also added to each of the 70. The output of the electronic switch device 64 is sent to an analog memory 72 which is coupled to an amplifier adapter 74 which is coupled to an actuating gear or actuator (not shown).

Before describing the method according to the invention, it is necessary to examine certain typical operating conditions.

Consider first a fuel-injected internal combustion engine with an intake manifold as shown in FIG. 3 with a single throttle valve for all cylinders. Under bench brake test driving conditions at constant engine speed and air temperature, the air intake is measured for different degrees of throttle valve opening. A characteristic diagram as shown in Fig. 1 is obtained, in which the horizontal axis shows the average pressure P _M in the intake manifold, the vertical axis shows the amount of air taken in per cycle Q _a , and the line drawn It is recognized that is a straight line that does not pass through the origin.

For example, atmospheric pressure may change as a result of climbing from sea level to a certain altitude. Although the pressure changes in the intake manifold,
It is indicated by chamber 8 in the figure. Because of the significant volume between each inlet valve and the throttle valve, the average pressure within the intake manifold is not appreciably affected by variations in atmospheric pressure. The reason for this is that at any given moment one of the cylinders of the engine is in the intake state, so a single throttle valve allows virtually continuous airflow into the intake manifold, and therefore at atmospheric pressure This is because changes in the density of the air as a result of variations in the inlet valve do not lead to significant differences between the pressure actually present in the cylinder downstream of its inlet valve and the average pressure measured in the manifold.

Therefore, in an air supply system with a single throttle valve, a single pressure sensor is used in the intake manifold just upstream of the inlet valve. In a four-stroke, four-cylinder engine with a single throttle valve, the four intake strokes span the entire operating cycle in unison, so the instantaneous pressure in the intake manifold downstream of the throttle valve will fluctuate slightly as a result of this. The average value of this pressure is then confused with its instantaneous value. In particular, this pressure shows a good approximation compared to the pressure of the air drawn into the cylinder upon closing of the associated inlet valve. In conclusion, for devices that regulate air with a single throttle valve, the average value of the absolute pressure in the intake manifold generally equals the mass of air inhaled per cycle given the equivalent of all other conditions. It is possible to establish a correlation, and this correlation can be said to be of a linear type.

In particular, the average value for a given temperature of the pressure downstream of the regulating throttle valve determines the density of the air taken into the cylinder, and for its re-evaluation in mass:
It is not necessary to know atmospheric pressure.

We now consider a particularly relevant case, namely a fuel-injected four-cylinder four-stroke internal combustion engine with one throttle valve per cylinder using an intake manifold as shown diagrammatically in FIG. The valves are connected and operated simultaneously by the vehicle's accelerator pedal. Assuming that this manifold is mounted on the same engine and bench tested to obtain a graphical curve corresponding to that shown in Figure 1, the intake manifold short section located between each throttle valve and its associated cylinder will be Tested under the same conditions, the curve shown in FIG. 2 is obtained from a detector measuring the pressure present in the tube. The horizontal axis in Figure 2 shows the average value P _{M of the absolute pressure inside the intake manifold, which was found by taking the average of the values obtained by the detector, and the vertical axis shows the average value P M} of the absolute pressure inside the intake manifold, which is taken into the engine in each operating cycle. Indicates the mass of air Q _a .

In this case, it is observed that variations in atmospheric pressure give rise to a family of curves. Experiments have shown that for a given throttle valve opening, it is not possible to obtain a unique correlation between the average pressure measured in the intake manifold and the intake air volume. The reason for the marked difference between the curves of FIG. 2 and FIG.
The volume in the manifold downstream of the throttle valve, which is characteristic of the single throttle valve manifold shown in Figure 4, is not present in the multiple throttle valve manifold of Figure 4, and the pressure measured in the intake manifold is significantly affected by fluctuations in atmospheric pressure. receive.

5 and 6 show the time difference between the instantaneous pressure P _i in one of the intake short pipes 4 of the manifold of FIG. 4 and the movement of the inlet valve in a four-cylinder, four-stroke engine of the type to which the invention relates. Graphical curves of representative fluctuations for large scales are shown, respectively. The vertical axis in Figure 5 is
The vertical axis of FIG. 6 shows the instantaneous pressure P _i and the lift h of any inlet valve associated with each of the respective short pipes 4 of the intake manifold of FIG. 4.

The time gap shown as A-B-C is 1 of the cylinder.
This is the time during which the inlet valve associated with the period is open.
During this time, the pressure P _i in the associated short pipe falls, while the respective piston moves down during its suction stroke until the valve closes (approximately at point C). Starting from point C, the pressure P _i increases and the air is drawn through the throttle valve and reaches the atmospheric pressure Patm after a more or less short time depending on the degree of closure of the throttle valve.
In Figs. 5 and 6, a strong chi-yoke state appears, and under this control, the pressure never reaches the atmospheric pressure value, but the intake period and the exhaust period overlap (in other words, As a result of the expansion of the exhaust gas into the intake conduit, atmospheric pressure is reached, which is even exceeded upon opening of the inlet valve.

During the time that the respective inlet valve opens, the pressure in the associated cylinder depends on the pressure in the intake conduit downstream of the respective throttle valve, which pressure is the pressure drop allowed in the volume calculations of the inlet valve itself. differs only by the pressure drop across the

On the other hand, the pressure inside the cylinder when the inlet valve is closed differs very slightly from the pressure P _C shown in FIG. Pressure P _C thus provides a good approximation, for a given temperature, of the magnitude of the air density occurring during the engine's operating cycle. Therefore, the pressure signal obtained from the sample cylinder at this instant can be used to determine the air flow rate.

The optimal moment for detecting the pressure signal depends primarily on the delay angle of the closing of the inlet valve and must in any case be determined by subsequent tests for each type of engine. This pressure must be detected with a suitable transducer that responds quickly enough so as not to appreciably distort the instantaneous signal even at high engine speeds. Using the electronic device described below, it is possible to detect this pressure only for specific values of the engine crankshaft angle. That is, pressure sampling is carried out at appropriate moments aligned with the angular position of the engine crankshaft. For an 1800c.c. engine with a 20° inlet valve closing delay, 10° to 30° after bottom dead center of the piston under test.
Experiments have shown that pressure sampling must be carried out at 15° to 20°. In any case, the optimum time is very close to the closure of the inlet valve. Under these conditions, if a device for regulating the intake air having as many throttle valves as cylinders takes as its parameter, instead of the average pressure, the pressure taken at a suitable phase of the engine shaft rotation. , is completely equivalent to a device with a single throttle valve. In particular, the sampled pressure and the instantaneous engine speed (engine speed) form a pair of independent parameters that are recognized as unambiguous and with a good approximation of the operating point of the engine, so that the engine Starting each time as if it were to function under conditions corresponding to the same pair of parameters, and except for temperature correction, the amount of intake air was
are the same.

An apparatus for carrying out the method according to the invention will be described with reference to FIG. 7, which is a program diagram of one embodiment of the apparatus.

A sound wheel 16 of known type is mounted on a not-shown crankshaft of a fuel-injected engine so as to rotate at engine speed. The wheel 16 is
It has two sets of teeth. The first set of teeth 23 are spaced at regular intervals around the periphery of the wheel to allow evaluation of the crank angle measured by the pick-up 22. The second set of teeth of the wheel 16 consists of two teeth 18 corresponding only to the top and bottom dead centers detected by the pick-up or detector 20.

Splined to the camshaft of an engine (not shown) rotating at half the speed of the crankshaft is a wheel 10 having a single tooth 12 which transmits synchronized signals to a pick-up 14; , clearly has one pulse every two revolutions of the engine.

The mechanical device is constructed in this way, so that if it is desired to sample the pressure in the cylinder in which the pressure detector 8 is located, the optimum moment for this sampling is determined by the synchronized signal. It encompasses the interval between two successive signals of the dead center position measured from the arrival of .

The signals obtained from the pickups 14, 20, 22 are shaped by shaping circuits 24, 26, 28, respectively. The tuning signal from the pickup 14 is shaped or shaped and then sent to a bistable multioscillator 32 that sets it. AND gate 36 allows the dead center signal obtained from pickup 20 to pass. The signal from gate 36 is passed through a bistable multivibrator 41, and the output signal from vibrator 41 allows the signal from pickup 22 of the acoustic wheel to be passed through AND gate 44.

The tuning signal also resets the counter 50,
Therefore, the counter 50 starts from dead center and starts from tooth 2.
Each time one of 3 passes under the pick-up 22, the count advances by one.

The angular position of the engine crankshaft at which it is desired to sample the pressure signal detected by the transducer 8 is
is set in the angular position preselector 58 and the amplifier 60
When the counter 50 counts the number of teeth 23 corresponding to the engine crankshaft angle set in the preselector 58, the comparator 54 issues a signal that is sent to the electronic switch device 64. . Switch device 64 closes when a control signal is sent (in this case, this signal comes from comparator 54) and opens the circuit when there is no control signal. This results in
The variable pressure signal provided by amplifier 60 is only allowed to pass for a short moment equal to the duration of the control pulse provided by comparator 54 and is stored in memory 72 .

The memory 72 is consequently a small capacitor that is charged almost instantaneously to the value transmitted via the electronic switch device 64 and is used for the longest repeated period of sampling (i.e. engine idling). ) is discharged gradually through the corresponding resistor of the discharge circuit with a time constant significantly longer than . Amplifier adapter 74 transmits the signal received from memory 72 to a sample signal utilization device coupled downstream of adapter 74, not shown in FIG.

Adapter 74 has a high input impedance so that memory 72 functions best.
It has a low output impedance so that the utilization equipment connected downstream of it can function properly.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the variation of the intake air quantity Q _a as a function of the average pressure P _M for an internal combustion engine with four cylinders and a single throttle valve; FIG. Diagram of the same parameters as in FIG. 1 for an internal combustion engine with four cylinders, FIG. 3 is a schematic partial cross-section of the intake manifold with a single throttle valve, and FIG. 4 shows each engine cylinder. Schematic partial sectional view of an intake manifold with one throttle valve per cylinder, FIG. 5; diagram of the variation of the instantaneous pressure P _i of a cylinder with time t of a four-cylinder engine with one throttle valve per cylinder; FIG. The figures show a diagram of the periodic lift movement of the inlet valve corresponding to the cylinder of FIG. 5, and FIG. 7 shows a block diagram of an embodiment of the invention of an apparatus for carrying out the method of the invention. 4... Manifold short pipe, 6... Throttle valve, 8...
Pressure detector, 14... Tuning detector, 20... Dead center position detector, 22... Third pickup, 24,
26, 28... Molding device, 30... First input of first switch device, 32... First switch device, 34... First input terminal of first gate device, 3
6...First gate device, 38...Second input terminal of the first gate device, 40...First input terminal of the second switch device, 41...Second switch device, 4
2...First input terminal of the second switch device, 44
... second gate device, 46 ... second input terminal of second gate device, 48 ... first input terminal of counter, 50 ... counter, 52 ... second input terminal of counter
Input terminal, 53... First input terminal of comparator, 54
... Comparator, 56 ... Second input terminal of comparator, 5
8... Angular position preselector, 60... Multiplier, 62
...first input terminal of the switch device, 64...switch device, 66...second input terminal of the switch device, 68...second input terminal of the first switch device, 70...of the second switch device Second input terminal, 72...memory.

Claims (1)

[Scope of Claim] A method for measuring the flow rate of air taken into a four-cylinder fuel-injected oil-cycle engine having one throttle valve per cylinder, wherein the pressure of the intake air is at least 1.
The pressure signal of the pressure sensor is measured by a pressure sensor located between the inlet valve and the throttle valve of the two cylinders.
A method characterized in that the sample is taken within a precise range of the angular position of the engine crankshaft. 2. Patent claim applicable to an engine in which the closing of the inlet valve is delayed by 20°, characterized in that the pressure signal is sampled between 15° and 25° after the bottom dead center position of the engine crankshaft. The method described in item 1. 3. An acoustic wheel that is rotated by the engine and cooperates with the pickup to generate pulses during rotation, a dead center position detector that detects the dead center position of a member rotating at the same speed as the engine, and a dead center position detector that detects the dead center position of a member rotating at the same speed as the engine. and a tuning detector associated with a member rotating at half the speed of the engine. a pressure detector 8 for detecting the pressure in the intake manifold short pipe 4 between the associated inlet valve of the cylinder and the throttle valve 6;
and; an amplifier 60 for the pressure signal from the pressure sensor.
a switch device 64 having a second input terminal 66 and a first input terminal 62 coupled to the output terminal of the amplifier 60; first and second input terminals 3;
0,68; a first input terminal 34 connected to the output terminal of the first switch device 32 and the dead center position detector 20;
a first gating device 36 having a second input terminal 38 coupled to; a first input terminal 40 and a second input terminal 7 coupled to the output terminal of the first gating device;
a device 41 for a second switch having a value of 0;
The first one connected to the output terminal of the switch device 41
a second gating device 44 having an input terminal 42 and a second input terminal 46 to which a pulse signal from the pick-up 22 of said acoustic wheel is applied; a counter 50 having two input terminals 52; a pick-up 22 of the acoustic wheel;
the output signal of the dead center position detector 20 and the first pulse output signal of the first switch device 32.
a shaping device 24, 26, 28 for shaping the tuning signal of the tuning detector 14 applied to the input 30 and the first input 52 of the counter 50; an angular position preselector 58; an output terminal of the counter 50; a first input terminal 53 connected to the angular position preselector 58; and a second input terminal 5 connected to the output terminal of the angular position preselector 58.
6, and a comparator 54 having an output terminal coupled to both a second input terminal 68 of the first switching device 32 and a first input terminal 66 of the switching device 64; A measuring device characterized in that it comprises: a memory 72 having a connected input terminal and providing a pressure signal indicative of the intake air flow within a certain range of angular position of the engine crankshaft. 4. The measuring device according to claim 3, wherein the memory 72 includes a capacitor. 5. The measuring device according to claim 3 or 4, wherein the switch device 64 includes an electronic switch. 6. The switching device 32, 41 comprises a respective bistable multioscillator having a setting input terminal and a resetting input terminal. Measuring device according to item 1. 7. Claim 3, wherein the gate devices 36, 44 include AND gates.
6. The measuring device according to any one of items 6 to 6.