FR2466618A1 - FUEL CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Fuel control system for controlling the amount of fuel supplied to an internal combustion engine in accordance with the power desired by the operator to be delivered by the engine. System comprising: a multiplier 30 receiving a signal representative of the quantity of fuel sent to the engine and a signal representative of the speed of the engine in order to multiply them and generate a signal representative of the power delivered by the engine; a comparator 12 for comparing this latter signal with an operator power control signal and generating an error signal representative of their difference; and a counting device 20 receiving the error signal and intended to modify the quantity of fuel sent to the engine by acting on a pulse generator 22 in order to make the error signal tend towards zero. System applicable to passenger vehicles. (CF DRAWING IN BOPI)

Description

The present invention relates generally to a

  fuel control system for a combustion engine

  tion and, more particularly, to such a system of

  fuel control for a vehicle presenting a report

  high power / weight port, whereby an operator controlled power signal is compared to a detected power signal to control the engine response

  the difference between these signals.

  While the present invention will be described

  in connection with a diesel engine, it must be understood that

  the basic principles of the invention also apply to spark ignition engines. In a conventional diesel engine with a power control unit in

  electronic fuel, the controller generally works-

  speed controller and in many cases this type of control gives complete satisfaction. However, with a passenger vehicle with a power / weight ratio

  relatively high, the response of this vehicle, or its maneuver

  true, suffers somewhat from the control performed by a conventional speed control device, since small variations of the operator's control input

  give rise to large variations in the torque of

engine.

  In conventional spark-ignition engines, before the application of severe control constraints

  emission of exhaust gases and their operation in

  Very poor engine to improve fuel economy, these engines were powered in rich mode. With such a mode of operation, the output torque of the engine is proportional to the pressure in the intake manifold that results from the air passing through the throttle plate to go

  to the cylinders. The throttle plate acts as a choke

  on the air going to the cylinders. When the pressure at any orifice, for example the orifice created by the throttle plate, comes to exceed with the total inlet pressure a certain ratio, the speed of the air particles

  in the hole becomes sonic. This type of flow is de-

  named sonic or critical flow. Under these conditions, the quantity of air passing through the orifice is independent of the pressure downstream of the orifice and is only influenced by the

246661 8

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  pressure upstream and the area of the orifice.

  When an ignition engine. conventional control operates with a tightly closed throttle, this engine is operated with a constant air / fuel nominal ratio and the output power is directly connected to

  the flow of air. Since this flow depends only on

  than the area of the aperture during the hearing.

  The output power of the motor is therefore directly connected to this area which, in turn, is directly related to the rotation of the throttle caused by

the operator. -

  Such an operating characteristic, i.e., the direct relationship between throttle plate displacement and output power, is considered by most drivers to be a good maneuverability or a good response characteristic of the driver.

  motor in response to a variation of the throttle position.

  The present invention aims a device providing this type of power control giving good maneuverability along a wide range of movement of the butterfly. Therefore, the present invention as applied to

  control of the fuel of a diesel engine, helps to improve

  the response characteristic of the motor to the displacement

  butterfly and therefore the comfort of driving without

  both sacrificing the emission characteristics-gas

  exhaust or vehicle performance.

  Therefore, an object of the present invention is to improve the maneuverability characteristic

  a vehicle equipped with an internal combustion engine.

  This and other objects and features of the present invention will become more clearly apparent.

  of the following detailed description and the attached drawing

  whose unique figure represents a schematic diagram of the

positive according to the invention.

  In a diesel engine that is still powered

  in a lean regime compared to the stoichiometric point, gen-

  very poor, it has been found empirically that the

  output torque is directly related to the amount of

  injected fuel per cycle. Naturally, the power can be derived from the speed and torque in the following way - 3- Power = K (torque..speed)

  with the factor K representing a constant of proportio-

  ality. Therefore, in the system according to the present invention, the operator input reflects a power level requirement. By means of calculations carried out in an electronic control unit, the actual power

  delivered is calculated by detecting the amount of fuel

  delivered and the speed of the engine in order to obtain a

  representative of the quantity of fuel per revolu-

  motor and this signal is used to represent the actual power delivered. This calculated power signal is compared to a controlled power signal obtained from the operator input to generate an error signal. This signal controls the system so as to reduce the error and,

  thus, to maintain the commanded power level. obviously

  There is an upper limit of the power of

  engine output for any given speed. This limit

  The lower limit is recognized by the electronic control unit, the power limit being generally proportional to the speed, and the amount of fuel sent to the engine is limited to that used by this engine. Also, exhaust emission characteristics, stress levels and other parameters are taken into account.

  when establishing the electronic control unit.

  During the production of the error signal, the correction process used in the system according to the invention enables

  to operate the fuel supply control system

  to provide a suitable pulse for the fuel injectors to ensure that the power level controlled by the operator is developed by the engine. This same process can be applied to a spark ignition engine with some calculation corrections due to variations in the air / fuel ratios, although

  that as long as the engine is operated in a lean

  port at stoichiometric point the output torque can be further considered to be directly related to the amount of fuel per cycle. In cases where the air / fuel ratio varies or the engine is operated in a rich regime with respect to the stoichiometric point, so that all the oxygen available in the cylinders is used, corrections must be made in himself

  based on parameters such as pressure in the tubing

  lure intake and temperature. Therefore, as soon as the throttle is moved, the power level rises to the new power point as determined by the area of the throttle port to its new position and, when the engine resumes, the power remains the same. In

  In addition, the torque is reduced, allowing the perfor-

  engine speed to cross a road load curve

  on a diagram of the torque as a function of the speed of the

  in power control conditions.

  A motor with this characteristic of regeneration

  transient response is considered to provide an excellent

  slow maneuverability. However, in order to control

  exhaust emissions and fuel economy

  tible, it may be desirable to remove the fine edge that occurs when transferring a power level to

  another during the initial variation of the papillate

  lon. Also, towards the desired speed, as shown

  by the new power level, the slope of the

  torque risk as a function of engine speed can

  be slightly steeper to provide better

  their speed stability on the road.

  Referring to the single figure of the drawing, there is shown that an operator control signal representative of the controlled power is applied to an input driver.

  10. This signal is representative of the desired power level

  by the operator as controlled by the position of the -

  butterfly plate. The control signal, suitably

  proportioned, is addressed to an input of a comparator 12.

  The other input of this comparator receives from a driver

  input 14 a fuel quantity signal per revolution

  engine. This signal is representative of the power

  generated by the engine. In the case where the driving power

  by the operator, as represented by the signal appear-

  to the driver 10, and the power generated by the

  as represented by the signal appearing in the con-

  driver 14, are different, an error signal is -5-

  applied to a conductor 16 and is representative of the difference

  power expressed by the difference between the two

applied signals.

  The signal appearing to the driver 16 is addressed

  it is a universal counter 20 having a count and this signal increments or decrements the count according to its polarity. The output signal of the counter 20 is applied

  to a pulse generator 22 by a limiter 24. The limitation

  is used to limit the signal to a maximum value

  which can be addressed to the pulse generator 22. The

  The signal delivered by the pulse generator 22 is a fuel supply pulse signal which is addressed to

  the injector by a power amplifier 24 and a con-

  output driver 26. The output signal applied to the

  noide of the injector that is connected to the driver 26 is con-

  tripped by a trigger pulse generated by the uni-

  electronic control unit and applied to a driver

28.

  The feedback circuit intended to generate the

  actual power signal that appears to the driver 14 com-

  takes a multiplier circuit 30 with two inputs, one of which receives a driver 32 the pulse signal generated

  by the pulse generator 22 whose duration is

  the quantity of fuel delivered by the impulse

  corresponding fuel pressure. This signal is multiplied by a motor speed signal addressed to the other input of the multiplier circuit 30 by a conductor 36 which is connected to a speed sensor. Therefore, the signal delivered by the multiplier circuit 30 is representative of the amount of fuel sent to the engine. As previously mentioned, this amount of fuel

  is directly related to the power generated by the

tor.

  The limiter 24 receives by a driver 44 a seat

  general from a limit table storage means

  An air / fuel ratio system 40 which, in turn, receives, on the one hand, the speed signal from the conductor 36 and, on the other hand, a mass density signal of air from a suitable sensor connected to a conductor. 42. Therefore, the combination of the speed signals and the

  mass density of air. provides a signal that appears

  driver 44 which dictates the maximum pulse width which

  can be generated by the pulse generator 22.-The limit

  24 acts to limit to a maximum value the signal by which the counter 20 can be incremented.

  In operation, the operator changes the posi-

  the throttle plate, for example by increasing its angle of deflection. The input signal appearing at the conductor 10 is thus modified and generates an error signal which is delivered by the comparator 12 of the. does that signal

  appearing to the driver 14 represents the previous

  power generation. This error signal modifies the count of the counter 20 so as to increase the pulse width of the

  signal delivered by the power amplifier 24. This

  true as long as the limit of storage medium 40 is

not exceeded.

  Consequently, the fuel control system which has just been described makes it possible to control the fuel sent to an internal combustion engine in accordance with the

  desired power to be drawn from this engine. While the-

  signal obtained by multiplying the pulse width of

  the engine speed does not match exactly

  the power of the engine, it is nonetheless

  to this power in a frank manner. The multiplication

  the two signals is appropriate for the purpose sought by the

  power control to produce a pre-existing level of

  heightened maneuverability. Modifications may be

  worn to refine the control layout or change the

  how the data signals are processed without departing

  ter for that of the spirit of the invention. For example, a

  positive delay can be introduced into the feedback circuit between the pulse generator 22 and the circuit

  multiplier 30 to maintain the stability of the system.

  Also, the system could be modified in such a way

  create the air / fuel ratio limiter in the cir-

  cooks the input control signal so that the operator-controlled power signal represents a percentage of the maximum value of the fuel amount per cycle

which can be addressed to the engine.

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Claims (3)

  -1. A fuel control system for controlling the amount of fuel delivered to an internal combustion engine in accordance with the power desired by the operator to be delivered by the engine, characterized in that   what it includes: a way to generate a communication signal   operator power demand; means (32,36) for detecting   motor operating parameters representative of the power delivered by the motor having a means (32)   to provide a signal representative of the amount of   motor-addressed bile and means (36) for providing a signal representative of the engine speed; means (30) for multiplying the fuel quantity and engine speed signals and providing a signal representative of the power output from the engine; a way (12) to compare   this last signal to the operating power control signal   to generate an error signal representative of their difference; and means (20) connected to receive the signal   from the comparator means (12) for modifying   proud of the amount of fuel sent to the engine in order to   set the error signal to zero.   2. System according to claim 1, characterized   in that the motor is powered by compression pulses   in that the means (20) for modifying the quantity of fuel sent to the engine makes it possible to   vary the width of the fuel pulses.   3. System according to claim 1, characterized in that there is provided means (24, 40) for limiting to a   maximum value the amount of fuel sent to the engine.