FR2509378A1 - CARBURETOR WITH AUTOMATIC CONTROL OF THE COLD STARTING FLAP - Google Patents

Abstract

THIS CARBURETOR INCLUDES A COLD START FLAP 6 AND A THROTTLE CORRECTOR 15 4. THE PLATES 21, 22 OF THE MEMBRANE 23 OF THIS CORRECTOR INCLUDE A VALVE 31 FOR MAKING THE ATMOSPHERE OF THE WORKING CHAMBER 25 OF THE CORRECTOR. THIS VALVE IS CONTROLLED AS A FUNCTION OF A CAM 34 MOVED IN ROTATION BY A BIMETALLIC SPRING 37; ITS OPENING IMMOBILIZES THE RETURN OF THE THROTTLE 4. THIS CARBURETOR ALLOWS COMPLETELY AUTOMATION OF THE COLD START, TEMPERATURE AND SPEED ADJUSTMENT PHASES OF THE INTERNAL COMBUSTION ENGINE WHICH IS EQUIPPED WITH IT.

Description

_-1 _-

  The present invention relates to a carburetor for internal combustion engines which compress a mixture of fuel and oxidant, this carburetor comprising a main fuel supply system which opens into a zone of the diffuser of the intake manifold, a system of feed of idle fuel which opens downstream of a throttle valve which can be operated at will and located downstream of the diffuser, and a cold start flap which is arranged in the air inlet of the intake manifold and which, in known manner, is actuated by suitable devices as a function of the temperature, the suction pressure, the air flow rate and the load

on the engine.

  Carburetors of this kind are used for engine operation in motor vehicles.

  who must meet certain conditions

  of regulations imposed by legislation on the content of exhaust gases in harmful substances, hence

  high quality requirements for these fuels

  in order to purify the exhaust gases,

  fuel economy and good road performance

age.

  It is to meet these requirements that the carbura-

  Torers are equipped with various systems intervening in specific operating or load ranges. Among these, the cold running of the engine and the idling must be considered to pose particular problems, this is why many provisions have already been proposed in view of solving these problems Among these # the device described in patent application DE-OS 24 46 403 is particularly remarkable It is a

  engine speed stabilization device

  slowed down after being launched, with a carburetor comprising a) a cold start flap mounted eccentrically and actuated by an elastic member sensitive to temperature and by ltir penetrating into the intake manifold, 2 - b) a throttle valve controlled by a vacuum regulator responding to the vacuum prevailing in the intake manifold, and c) a system for dosing a greater quantity of mixture when the engine is cold This stabilization device is characterized by the fact that the dosing system of greater

  amount of mixture when the engine is * roid is cons-

  titud by a stop which is pivotally mounted, is connected

  temperature, and when the temperature

  low ambient temperature, supports the butterfly in a

  position of greatest opening and does not release it completely-

  when the engine has reached a temperature below

  completed, after which control is provided directly by the vacuum regulator; the temperature-sensitive element preferably consists of a bimetallic spring. With a device as described in patent application DE-OS 24 46 403 it must be possible, in particular

  after starting the engine, give the throttle a posi-

  precise opening function which depends on the am-

  biante at the time of launching and the engine speed (suction pressure) However, this is only possible, with the said known device, only for a short period

  after the engine has started.

  Another command to open the throttle valve

  glement, dependent on the bimetallic spring, is not provided and is not possible either because of decoupling

  of the cold start flap in the opening direction.

  In the daily case of a prolonged idling phase after starting the engine, for example in a traffic "traffic jam", before a red light or a closed level crossing, malfunctions occur due to the blocking of the return of the stopper by friction and the force with which the closing spring presses on the operating rod when the vacuum regulator

  is at the end of its travel The blocking of the stop has the consequence of

  3 - quence that, the engine temperature rising, it produces an increase in the speed of the engine i this increase does not stop that when the engine is subjected to a load, by the fact that the stopper is released and can, under the effect of gravity, support the shutter

  cold start or bimetallic spring movement.

  For this speed range, no means are provided ensuring a minimum slit of the throttle valve in other words, this slit depends only on the characteristic of the vacuum regulator, which must however be calculated for the hot running of the engine, which is subject to criteria other than idling

  cold, for example the purification of exhaust gases.

  The subject of US patent 4,181,107 is so far

  Tement to remedy these shortcomings According to this patent the positioning of the throttle valve must be controlled by an expandable element which, as we know, is

  capable of exerting great displacement efforts, contra-

  rement with bimetallic spring i but an expandable element naturally has a large hysteresis, is subject to disturbance and may, as it ages, exhibit large deviations with regard to its adjustment and its operating characteristic Regulation of the vacuum is not

  not contemplated in this US patent.

  The problem to which the invention provides a solution was therefore to equip a carburetor of the type described in the preamble with a device which makes it possible to ensure that the cold start and the rise in temperature of the engine take place entirely automatically, that is -to say

  without requiring any other intervention on the part of the conduc-

  to start the engine, this device also having to ensure that the speed of rotation slows down, which must intervene when the internal combustion engine is subjected to a greater load; for example,

  in modern vehicles, when the Wine compressor

  air conditioning or hydraulic pump of a -4

  automatic gearbox are started.

  The solution that the invention has designed to solve this problem consists in the following combination of partially known characteristics sa) a throttle valve corrector, comprising a membrane and a pneumatic return of this throttle valve in the closed position depending on the suction pressure, influences the closed position of the throttle valve, b) a thermal positioner, controlled by the heat of the engine and / or of the heating, limits the return movement by the fact that c) a valve by which the work can be vented can be moved with the membrane depending on the suction pressure, d) the movement of this valve takes place relative to a thermal element in the form of a bimetallic spring, and

  e) this spring carries a cane which moves in function

  tion of the temperature and activates the said valve.

  Thanks to the invention we have reached a possibility of harmonization of the characteristics oriented only on the function to be ensured by each of the systems, and this despite the overlapping of their effects that, for the first time, the combination according to the invention made it possible,

  which is a surprising result.

  Another advantage of this combination is the

  Lely fully automatic engine launch phase and its temperature rise, this phase can take place regardless of the engine speed, therefore also in idle speed, which ensures a considerable decrease in the emission of toxic bodies For than

  in cold areas of the globe a motor vehicle iui S-

  to be operational, for the auxiliary devices of this vehicle to operate, the engine must have reached a minimum temperature before starting the vehicle - running; this is made possible by the invention, while so far only so-called vehicles

  high-end, equipped with an injection or a carburetor

  tor fitted with a bypass thermal choke,

  owe to this necessity Now, the manufacturing technique

  tion of a bypass choke is complex and costly.

  The combination according to the invention therefore constitutes a real alternative to such a starter; she is

  much simpler operation, dlune fabrica-

  tion and less costly in-service maintenance Employment,

  to constitute the combination according to the invention, by

  Proven carburetor ties guarantee perfect engine operation for a long time. An exemplary embodiment of the invention is shown

  schematically in the appended drawing to which the description refers

  the following description.

  The carburetor shown in the drawing is equipped with a main fuel supply system 3 which opens into the diffuser 1 from an intake manifold 2, an idle fuel supply system which opens into the manifold d intake 2 downstream of a throttle valve 4 operated at will and located downstream of the diffuser 1, and of a cold start flap 6 which is arranged in the air inlet of the intake manifold 2 and which is actuated, in a known manner, by suitable devices

  depending on the temperature, the suction pressure

  air flow and load on the engine, -.

  This carburetor has all the devices allowing it to function perfectly, even if these are not

shown in the drawing.

  The throttle valve 4 is fixed on wu tree,?

  at the free end of which is placed a lever for

  work 8 with hanging holes 9.10 for a spring 11 etin operating device 12 g this lever also includes stop tabs 13.14 for a slot adjustment 6-

  minimum and a throttle corrector 15.

  This corrector 15 is screwed onto the carburetor by means of a support arm 16 and comprises an axis 17 with an adjusting screw 18 and a locking nut 19 This axis is mounted to slide axially in a casing 20 and is connected, by means of two plates 21, 22, to a membrane 23 the edge of which is clamped between the casing 20 and a cover 24 This membrane isolates from a chamber 27 of the casing 20 communicating with the atmosphere

  the working chamber 25, the latter being, by the

  end of a vacuum line 26, connected to the intake manifold 2 downstream of the butterfly valve 4 On a thread of the axis 17 is placed a adjusting nut 28

  the effective length of a pre-stressed spring 29

  tre the housing 20 and the axis 17 This spring pushes the axis 17 and the adjusting screw 18 against the stop tab 14 when the diaphragm plate 21 touches the housing 20, so that with the screw 18 you can adjust an opening

maximum throttle 4.

  Between the diaphragm plates 21, 22 is disposed parallel to the axis 17 a discharge conduit 32 whose sectinn is controlled by a valve 31 subjected to the action of a spring 30 The latter pushes back into the working chamber 25 the stem 33 of the valve, which, when the axis 17 moves against the force of the spring 29, is applied against a control cam 34 fixed on a shaft rotatably mounted in the cover 24 A bimetallic torsion spring 37 is engaged by one end 38 in the free end of the shaft 35, while by its other end 36 it is engaged in a cover plate 39 which can be rotated -The part of the chamber

  working 25 in which is arranged the bimetal spring-

  lique 37 has a heat exchange zone 40 which

  receives engine cooling water; alternatively or in addition, an electric heater 41 can be provided in said part of the-chamber 25 This part can be -7 - possibly separated from the rest of the chamber 25 by

watertight partitioning.

Description of operation

  When the engine must be restarted after it has cooled down, the state of

  things following S the cold start flap 6 has been postponed

  s 6 in its closed position by a device (not shown

  sensed) sensitive to temperature, and the butterfly corrector 15 placed the butterfly 4 in the position of entes

  1 o maximum, the bimetallic spring 37 having, in the cor-

  rector 15, a function of the cooling temperature

  engine, moved almost without exerting force

  cam 34 to make it occupy a corresponding position

dante.

  The vehicle operator immediately starts the

  without doing anything else, and given

  that the cold start flap 6 is closed and that the paper

  lon 4 presents its maximum opening, the suction pressure

  ration acts directly on supply systems 3 and 5

  When the engine is started With the bolster 6 re-

  nifle and is put in the minimum open position by the

  suction pressure drop, via the

  positive with manometric capsule ("pulldown"), while the butterfly corrector 15, also urged by the suction pressure, causes the axis 17 to move back, so that the butterfly 4, under the action of the closing spring 11,

  is moved towards its mid-slot position

  minimum The cam 37 controlled by the bimetallic spring 37 has a shape such that, at low temperature, the recoil stroke of the axis 17 is small until the rod

  valve 33 meets cam 34, while at high temperature

  This stroke is large When this rod 33 returns

  against the cam 34 the force of the spring 30 ends up being overcome, so that the valve 31 opens and releases the

  discharge conduit 32, which means that the working chamber

  vail 25 is vented and that, as a result of the effective pressure drop on the diaphragm 23, the booster stops as the

  engine warms up, bimetallic spring 37? warms up

  fe him asi in parallel, the choke flap 6 is moved as well as the cam 34, this 1 erniére not subject

  that the force exerted on it by the spring 30 by the

  through valve stem 33, and this force is

  easily defeated by that of the bimetallic spring 37.

  Independently of one another, the opening of the choke flap 6 can precede the closing of the throttle valve 4 to the minimum slit, which is necessary in particular in modern engines because the power which they consume by friction must be supplied. leaving the butterfly

  4 (quantity) opened long enough, while the enrich-

  mixture by opening the cold start flap

  6 (quality) can be removed much earlier.

  Since the bimetallic spring is able, under the effect of a determined temperature variation, to provide large amplitude adjustment strokes, a pilot cam 34 exactly adaptable to the needs of the engine

  can be designed, and the small amplitude of the adjustment possible

  ble allows continuous movement of the bimetallic spring; in other words, when variations occur

  temperature only excess voltages can occur

  sives are generated in the material by hindering the torsion of the spring When the butterfly approaches the minimum slit position, the regulation by the corrector can already come into action if the need arises (additional load due to accessory devices),

  at the same time as by venting other functions

  can be insured (eg arrival stop

  fuel in engine brake speed, etc.).

9 -

Claims (1)

CLAIM.   Internal combustion powertrain carburetor which compresses a mixture of fuel and oxidant, this   carburetor, which has a fuel supply system   main rant which opens into an area of the diffuser   of the intake manifold, a fuel supply system   idling rant which opens downstream of a foreign butterfly   freely manageable control located downstream of the diff   fuser, and a cold start flap which is arranged in the air inlet of the intake manifold and which, in known manner, is actuated by suitable devices according to the temperature, from the pressure to the aspiration,   of the air flow and the load on the motor, being noted   due to the following combination of characteristics partially known: -   a) a corrector (15) of the throttle valve (4), comprising a membrane (23) and a pneumatic return of this butterfly in the closed position as a function of the suction pressure, influences the closed position of the butterfly (4), b) a thermal positioning member (37) controlled by the heat of the engine and / or of the heating, limits the return movement by the fact that c) a valve (31) by which the working chamber (25) can be vented can be moved   with the diaphragm (23) depending on the suction pressure ration,   d) the displacement of this valve (31) takes place relative-   ment to a thermal element in the form of a bimetal spring-   lique (37), and e) this spring (37) carries a cam (34) which moves as a function of the temperature and actuates the said valve (31).