FR2538856A1 - CARBURETOR WITH ELECTROVALVE ENRICHMENT CONTROL - Google Patents

Abstract

THE CARBURETOR INCLUDES A MAIN FUEL SPRINKLING CIRCUIT OPENING AT THE NECK OF A VENTURI 17 PLACED IN THE INTAKE DUCT 11 AND AN IDLE AND LOW-LOAD OPERATING CIRCUIT ENDING IN THE INTAKE DUCT BELOW AN ORGAN CHOKE 12 CONTROL BY THE DRIVER. AN ENRICHMENT DEVICE PROVIDES AN ADDITIONAL FUEL SUPPLY TO THE INTAKE DUCT DURING CERTAIN PHASES OF OPERATION. THIS DEVICE INCLUDES AN ADJUSTING SOLENOID VALVE 40 POWERED BY AN ELECTRONIC CIRCUIT 41 CAPABLE OF PROVIDING VARIABLE CYCLICAL RATIO CONTROL PULSES. THE SOLENOID VALVE 40 IS PLACED ON THE DISCHARGE CHANNEL 26 OF A RECOVERY PUMP 23. THE PUMP IS PROVIDED SO THAT THE DEPRESSION WHICH IS IN THE INTAKE DUCT IS CAPABLE OF SUMPING FUEL THROUGH THE PUMP.

Description

l - Carburetor with enrichment control by solenoid valve This

  The invention relates to carburetors for internal combustion engines of the type which include

  a main fuel spouting circuit

  : edge at the neck of a venturi placed in the intake duct, a low-load idling and walking circuit emerging

  in the intake duct downstream of a choke member-

  controlled by the driver and an enrichment device

  sement to bring additional fuel to the intake duct during certain operating phases of an engine powered by the carburetor, device provided with an adjustment solenoid valve powered by an electronic circuit sensitive to at least one engine operating parameter and capable of providing ratio control pulses

variable cyclic.

  Among the carburetors of this type, one can in particular

  cite that described in patent application FR-A-2 419 403.

  The enrichment device, designed to charge the fuel

  tible both in the venturi and in an air channel of the idling circuit, is controlled by an electronic circuit intended to bring the air / petrol mixture supplied to the engine

  to the stoichiometric composition This solves the pro-

  engine operating problems in steady state, both at high load and at low load But it is not possible to operate a motor properly by providing it, at all speeds, a stoichiometric mixture of air and petrol Certain operating phases, such as acceleration, cold running or full load, make it necessary or at least desirable to supply the engine with a rich mixture. To achieve this result, independent circuits have generally been provided up to now. to fulfill various functions But it is difficult to control in a simple way the flow of fuel supplied by the various circuits so that the composition and the quantity of mixture

  supplied to the engine at all speeds are satisfactory.

  The present invention aims to provide a carburetor which meets the requirements of practice better than those previously known, in particular in that it makes it possible to satisfactorily adjust the richness of the mixture supplied to the engine, at all speeds, using only simple means.

  To this end, the invention proposes in particular a carbura-

  tor of the kind defined above, characterized in particular in that it comprises a recovery pump provided with an intake duct equipped with a non-return valve and a duct

  discharge supplying the intake duct and the circuit

  fuel idling, on which said solenoid valve is interposed, the pump being provided so that the vacuum which prevails in the intake duct is capable

  draw fuel through the pump.

  In an advantageous embodiment of the invention,

  the pump discharge pipe opens into the con-

  intake, near the venturi pass, via the

  median of two coaxial passages separated by a chamber communicating with the idle circuit of the carburetor, which does not comprise any other fuel supply than the

acceleration pump.

  So that a failure of the electronic circuit results in degraded, but still acceptable, functioning of the carburetor and not by an almost impossibility of starting the engine and making it run cold,

  the solenoid valve is advantageously of the type open at rest.

  To avoid a risk of self-ignition when the engine stops, it is advisable to provide the electronic circuit with a time delay which keeps the solenoid valve closed for

  a determined time interval after switching off the ignition.

  This same circuit can be provided to cut off the supply of fuel to the engine during deceleration operation, that is to say when the engine is running above a speed.

  predetermined while the butterfly is in the open position

minimum size.

  We see that the invention makes it possible to reduce to 1 the number -3 of solenoid valves required to fulfill several functions of very different nature, which constitutes a simplification

  very notable compared to the solutions previously proposed

  sées. Furthermore, the invention makes it possible to use a pump

  acceleration-controlled acceleration, that is, much

  stroke simpler than a pump controlled by a mechanical linkage from the main throttle member We know that the acceleration pumps controlled by vacuum have been abandoned practically at present due to their serious disadvantage: during when the engine stops, the acceleration pump injects its contents into the duct

  This drawback is avoided, in a par-

  particular implementation of the invention, by providing a

  narrow orifice of communication between the delivery chamber-

  acceleration pump and the constant level tank which supplies it The solenoid valve remains closed for a determined time interval after switching off the ignition, the discharge compartment of the acceleration pump is

  vacuum in the tank at constant level.

  The invention can be applied to car-

  burateurs-very different, and in particular to the carburettors known as constant depression, although it seems particularly interesting in the case of the carburetors known as depression

variable and fixed nozzle.

  The invention will be better understood on reading the

  following description of a variable vacuum carburetor which constitutes a particular embodiment given thereto

  title of nonlimiting example The description refers to the

  Single figure which accompanies it and shows those of the constituents of the carburetor which are concerned by the invention, in schematic form, partially in elevation and partially in

  vertical section through the axis of the intake duct.

  The internal carburetor shown in the Figure comprises a body (10) in several assembled parts in which is formed an intake duct 11 The lower part of the duct Il -4-

  contains a main throttling member formed by a

  pin 12 carried by a rotary axis 13 and controlled by the conduc-

  tor by means of a linkage not shown The upper part of the duct It constitutes an air inlet 14 generally provided with an air filter, not shown, and containing an air flap 21 appears

  relating to a starting system which will be described later.

  The fuel supply circuits to the engine are supplied by a tank 15 at constant level N This

  tank feeds a main circuit

  -10 bustible which will not be described in detail since it can be of conventional constitution It will generally include an emulsion well 47 supplied from the constant level tank 15 and connected to a passage 16 opening at the neck of a venturi 17 A idle and low load idle circuit comprises a channel 18 which opens downstream into the intake duct, on the one hand, through an idle orifice 19 located downstream of the

  slice of the butterfly 12 whatever the position of the latter

  negate and, on the other hand, by progression holes 20, also called "bypass holes", located so as to pass from upstream to downstream of the edge of the butterfly 12 when the latter is ajar from from its minimum opening position for

  bring it to the position shown in 12 a.

  The air flap 21 belonging to the starting device

  is carried by an eccentric pin 22 It is controlled either manually-

  Lement from a pull tab located on the dashboard, either automatically depending on the engine temperature,

  for example by a bimetallic strip This air flap 21 causes,

  that it is closed while the engine is running, a low pressure

  high at the outlet of the main spouting circuit.

  The carburetor further comprises an acceleration pump 23 The pump shown in the Figure, of the vacuum-controlled type, comprises a chamber of variable volume 24 connected to the tank 15 by a suction channel 25 provided with a valve d 25 a This chamber 24 is also connected to the intake duct by a discharge channel 26 La

2538856.

  -5- chamber 24 is bounded by a movable pumping member, constituted by a flexible membrane 29 which separates it from a chamber 30 connected by a channel 31 to the part of the intake duct 11 located downstream of the butterfly 12 A spring 32 contained in the chamber 30 tends to repress the membrane

  in a direction tending to decrease the volume of the chamber 24.

  A 45 th goal (not shown) can be provided to limit

this displacement.

  The operation of such a pump is well known.

  When the driver opens the throttle valve 12 while the engine

  turns, the depression decreases in chamber 30 and the res-

  fate 32 repels the membrane 29 and delivers fuel from the chamber 24 to the intake duct 11 The pump 23 also fulfills a role of enricher under load, the vacuum which then prevails at the neck of the venturi 17 being sufficient to suck fuel from room 24 to

the conduit -

  In the illustrated embodiment of the invention,

  a solenoid valve 40 intended to be controlled by pulses

  variable duty cycle is interposed on the discharge pipe 26 This solenoid valve is controlled

  by an electronic circuit 41 capable of supplying credits

  current levels with variable duty cycle between O and 1, ratio determined by the value of the input signals it receives from various sensors sensitive to parameters of

engine operation.

  The discharge channel of the pump is designed to be able to feed the intake duct either directly, near the neck of the venturi, or via channel 18 of the idle circuit. For this, the calibrated orifice 28 through which s fuel from channel 26 opens into channel 18 of the idling circuit Le

  passage 42 for supplying air to channel 18 is placed in the pro-

  along the injection orifice 28 In order for the injection into the intake duct to take place properly, the passage 42 is of larger cross section than that of the orifice 6 - 28: this is not of a particular subjection, an air inlet orifice always being of larger diameter

  to the associated fuel inlet.

  In order to avoid the drawback of the usual vacuum acceleration pumps, a small section orifice 43 connects the variable volume chamber 24 of the pump 23 to the

tank 15.

  The electronic circuit 41 constitutes a calculation unit

  allowing the cyclic ratio of the pulses supplied

  supplied to solenoid valve 40 from various input signals.

  The frequency of the pulses may be constant and fixed by an oscillator incorporated into circuit 41. More frequently, it will be fixed by the speed of the engine: it suffices for this to place, for example on the ignition distributor,

  a sensor providing one pulse per revolution.

  The input signals received by the sensor must be

  put to calculate the duty cycle to give to the pulses

  of the solenoid valve at idle and at full load.

  One can choose, as corresponding information, the speed of rotation of the motor V supplied by a sensor 45

  and the opening angle a of the butterfly 12, provided by a cap-

  Other parameters can be used, in particular

  the depression which prevails downstream of the butterfly 12.

  In addition, to calculate the duty cycle required during cold operation, a signal representative of the engine temperature must be supplied to the circuit 41. This signal can be obtained using a sensor 46 subjected to the

  engine cooling water temperature.

  In general, it will be advantageous to use a circuit 41

  comprising a memory of the so-called "cartographic" type, provided

  sant a value of the duty cycle for each pair of values V, a A the value provided by the memory is applied

  a correction coefficient, additive or multiplicative, function-

  tion of the temperature e Finally, the circuit 41 will include timing means, making it possible to supply a signal

  duty cycle 1 during a deter- mined time interval

  mined (usually a few seconds) after switching off the ignition. The operation of such a carburetor is then

  next, during the phases in which circuit 41 occurs.

  Engine idling and progress When the engine is idling, that is to say that the throttle valve 12 is in its minimum opening position and that the speed is low, the strong depression which prevails in the

  intake pipe It downstream of the butterfly sucks fuel-

  tible Drovenant from chamber 24 through a non-return valve, the channel 26 and the calibrated orifice 28 which plays the

  role of idle jet At the same time, the vacuum

  eirp of the emulsion air through the calibrated passage 42 The duty cycle of the signals supplied to the solenoid valve 40 is determined by the circuit 41 as a function of the temperature 8 of the engine, or of another parameter: this effect is combined

  to that of the air flap 21 which provides an energetic enrichment

  during the launch phase and during

  first seconds of operation.

  Interruption of the idling circuit during deceleration When the sensor 44 indicates that the throttle is closed and that the sensor 45 indicates that the speed exceeds a threshold corresponding to deceleration operation, the circuit 41 excites the solenoid valve 40 in direct current, which cut fuel supply to engine Element of circuit 41

  necessary for this function can be very simple and is limited

  ter at a door indicating the presence of both conditions.

  Possibly, a third condition (very severe depression

  te in the intake manifold, gear ratio engaged) can be provided It requires the presence of an additional sensor. Smothering when switching off the engine ignition On some engines, it is necessary to stop the supply of fuel through the idling circuit when switching off the engine ignition switch, to avoid that

  the latter does not continue to operate in self-ignition.

  -8- To achieve this result, it is sufficient that the circuit 41 is provided to supply, for a predetermined period of time after switching off the ignition, a continuous signal for closing the solenoid valve 40. This time delay allows more prevent the pump

  acceleration 23, if pneumatically operated, do not

  routes the fuel contained in chamber 24 to the conduit

  Admission 11 It is sufficient for this that the duration of

  tion (duration of closing of the solenoid valve 40 after switching off the ignition) is sufficient for the fuel contained in the chamber 24 to be returned to the tank at constant level

  through calibrated orifice 43 before reopening.

  Acceleration: When the butterfly valve 12 opens, the reduction in vacuum in chamber 30 causes the displacement of the

  membrane 29 by spring 32 (to the right in the Figure).

  Fuel is returned to the intake duct 11 by

  through the discharge channel 26, the cali

  bré 28 and passage 42 The orifice 43 returning to the tank is obviously of significantly smaller section than the orifice

  28 Passage 42, of larger cross section than the cali-

  break 28, advantageously has a frustoconical shape flared towards

the top.

  The circuit 41 can be provided to modulate the quantity of fuel sent by the pump 23 as a function of the engine temperature (or other parameters, for example the brutality of the acceleration) For this, the circuit 41 regulates the duty cycle opening of the solenoid valve 40 as a function of the representative temperature signal supplied by the sensor 46 or of any other signal representative of an acceleration parameter. It should be noted that

  obtain, from the opening signal provided by the cap-

  tor 44, an opening speed signal, bypass.

  Modulation of the richness at full engine load

  When the engine is running at full load,

  say that the butterfly 12 is wide open, the depression -9- which prevails at the neck of the venturi 17 sucks fuel from the chamber 24 via the passage 42, the orifice 28 and the discharge channel 26 Ce operating mode can be detected from the signals supplied by the sensors 44 and 45 The circuit 41 can be provided to then supply the solenoid valve 40 with a control signal whose duty cycle is determined by values preprogrammed as a function of one or more

  parameters, for example the motor speed.

  These values are contained in a memory associated with the

circuit 41.

  Cold engine operation: The carburetor shown in the Figure has a starting flap 21 which, when in the closed position

  o he is represented, ensures the high enrichment necessary

  when the engine is started The throttle valve is then kept in a slightly open position (position 12 indicated in dashed lines in the Figure) so that the vacuum generated

  by the engine is transmitted to the outlet of the jail-

  main smoothing 16 The air shutter control 21 and

  that of the butterfly can be ensured by conventional means

  siques, which it is therefore not necessary to describe here The starting flap 21 is-intended to open quickly after launching the engine The richness necessary for the proper functioning of the engine is subsequently ensured, during heating, by the circuit which sends a signal to the solenoid valve whose duty cycle is essentially

  function of the temperature signal supplied by the probe 46.

  Operation in stabilized operation at normal operating temperature: Circuit 41 can be provided to then supply

  the solenoid valve 40 a continuous current of permanent closure.

  But the circuit can also be provided to intervene then, using the fact that the vacuum, coming from the

  neck of the venturi and the idle channel 18, applied to the outlet

  from orifice 28, allows fuel to be drawn through - chamber 24 This flow rate can be adjusted by modulating the duty cycle of the solenoid valve control signals

  based on engine operating parameters.

  In particular, it is then possible to perform closed loop operation by supplying circuit 41 with a signal

  sensitive to the composition of the engine exhaust gases.

  This signal can be provided by a lambda 48 sensor (in half

  in the Figure) plunging into the exhaust manifold

ment 49.

  However, this complication will generally not be desirable, unless it is necessary to meet the requirements of binding pollution legislation. We will not describe here the constitution of circuit 41,

  because you can use many different layouts.

  However, it should be noted that - this circuit will generally include -

  a digital computing device, for example a micro-

  processor associated with a working RAM and with ROMs for storing preprogrammed values, as well

  that at least one analog-to-digital converter for

  vertize the analog parameters provided by the sensors

  in digital data usable by the computing unit.

  The invention is susceptible of numerous variant embodiments and, in particular, it is adaptable to a constant vacuum carburetor, in which an auxiliary throttle member movable as a function of the flow rate which traverses the intake duct gives a section of passage of fuel towards the intake duct a value depending on its position, itself representative

air flow.

-ú 538 856

Claims (9)

  1 Carburetor for internal combustion engine   as a main fuel spouting circuit opening at the neck of a venturi (17) placed in the intake duct of the carburetor, an idling and   step at low load opening into the intake duct   downstream of a throttle member (12) controlled by the driver and an enrichment device for supplying the intake duct with additional fuel during certain operating phases of an engine powered by the carburetor, device provided with an adjustment solenoid valve (40) supplied by a sensitive electronic circuit   at least one operating parameter of the motor and'ca-   able to supply variable duty cycle control pulses, characterized in that it comprises a recovery or acceleration pump (23) provided with an intake duct equipped with a non-return valve and a discharge channel (26) supplying the intake duct and the idling circuit with fuel, a channel on which said solenoid valve is interposed, the pump being provided so that the vacuum prevailing in the intake duct   be able to draw fuel through the pump.   2 Carburetor according to claim 1, characterized in that the discharge channel (26) of the pump opens into the intake duct, near the neck of the venturi, by means of two separate coaxial passages (28, 42) by a chamber communicating with the idle circuit (18) of the carburetor, which may not include any other   fuel supply as the acceleration pump.   3 Carburetor according to claim 2, characterized in that the passage (42) for communication between the chamber and the intake duct is of greater section than the passage (28) for communication of the discharge channel (26) with the idling circuit (18).   4 Carburetor according to claim 1, 2 or 3, characterized in that the solenoid valve (40) is of the open type 2538856 J   12 - at rest and in that the electronic circuit (41) includes a time delay for keeping the solenoid valve closed for a predetermined period after switching off the ignition of the motor.   5 Carburetor according to any one of claims   above, characterized in that the acceleration pump is of the vacuum-controlled type and has an orifice (43) for communication between the variable volume chamber   and the constant level tank (15) which feeds it.   6 Carburetor according to any one of claims   previous, characterized in that the electronic circuit   includes a calculation unit associated with a map memory   phique providing a value of the duty cycle of the signals applied to the solenoid valve for each pair of values of the motor speed and the opening angle of the throttling organ.   7 Carburetor according to claim 6, characterized in   that the electronic circuit is provided with a time sensor   engine temperature and in that it is intended to apply a correction coefficient, additive or multiplicative, to the   duty cycle as a function of said temperature.   8 Carburetor according to any one of claims   above, characterized in that said circuit comprises storage means making correspond a value of the duty cycle of signals applied to the solenoid valve to each temperature value during operation at cold idle.   9 Carburetor according to any one of claims   previous, characterized in that it includes an air flap   (21) quick opening after engine launch.   Carburetor according to any one of the claims   tions, characterized in that the electro-   is provided to maintain the solenoid valve in the closed position when the operating parameters of the   engine indicate deceleration operation.