EP0262027B1 - Carburettor with an automatic starting device - Google Patents

Description

The invention relates to carburetors for internal combustion engines, provided with an automatic starting device comprising a starting flap whose progressive opening, during the warming of the engine, is controlled by an element whose temperature increases as and as the engine warms up, such as for example a bimetallic spiral subjected to the temperature of the engine cooling water or a capsule containing a thermodilatable material.

The invention relates more particularly to carburetors which successively comprise, in an intake duct, from downstream to upstream, a throttling member operable by the user, the outlet of a main fuel spouting system and a flap starting load in the direction of closing by the temperature-sensitive element when this temperature is below a limit value and in the direction of opening by the air current which bypasses it.

Known carburetors of this kind generally also have a pneumatic element subjected to the vacuum which prevails in the intake duct downstream of the main throttling member and designed to give to the starting flap, as soon as the engine is running. itself, a minimum opening.

In carburetors fitted with such a pneumatic element, the high vacuum which prevails in the intake duct at the outlet of the main spouting system when the shutter is closed, makes it possible to obtain a rich air / fuel mixture while the engine is driven by the starter; the shutter opens partially as soon as the engine turns by itself, which avoids the blockage and the stalling of the engine by excess of wealth.

Existing devices of this type have a serious drawback. If the engine is started completely cold, for example having not been operated for several hours, and then stopped after a short period of time (for example after an operating period of one to three minutes), it is difficult to restart the engine immediately. Indeed, the engine cooling water did not have time to heat up significantly and the starting flap closes completely as soon as the engine stops. Consequently, the engine is again supplied with a very rich mixture during the new attempt to launch. However, the engine which has just turned does not need as much richness as that of an engine which has been stopped for several hours and often this excess of richness makes launching difficult.

We already know (DE-A-3 028 629) a carburetor according to the preamble of the claim, constituted so as to avoid excessive dryness of the mixture supplied to the engine during certain phases of the cold start.

The present invention aims to provide a carburetor with a starting device that better meets those previously known than the requirements of practice, in particular in that it allows a restart of the cold engine very shortly after stopping, that is to say to solve a problem different from the previous one.

To this end, the invention provides a carburetor according to claim 1 or claim 4.

There is also known (US-A-3248 675) an enrichment device intended to take into account that the thermosensitive element of a carburetor cools down much faster than the mass of the engine and can cause an enrichment much higher than that which is acceptable for a hot engine. It is absolutely not the result sought by the invention, which adapts the wealth then even the engine has barely warmed up. Document US-A-3248 675 in fact uses a control as a function of the temperature, and not as a function of the elapsed time.

Secondary features of the invention are defined in claims 2 and 3.

• la figure 1 est une vue, en élévation et en coupe partielle suivant un plan vertical, d'un carburateur muni d'un dispositif de départ suivant l'invention, l'organe de butée du dispositif de départ étant représenté dans sa position de repos imposant une ouverture partielle au volet de départ ;
• la figure 2, similaire à la figure 1, montre un carburateur démuni d'élément pneumatique d'ouverture partielle du volet de départ, l'organe de butée remplissant également le rôle habituellement dévolu à cet élément pneumatique.

The invention will be better understood on reading the following description of inverted carburetors which constitute embodiments given by way of nonlimiting examples. The description refers to the accompanying drawings, in which:

• Figure 1 is a view, in elevation and in partial section along a vertical plane, of a carburetor provided with a starting device according to the invention, the abutment member of the starting device being shown in its rest position imposing a partial opening to the starting flap;
• Figure 2, similar to Figure 1, shows a carburetor devoid of pneumatic element partially opening the starting flap, the stop member also fulfilling the role usually assigned to this pneumatic element.

• un organe d'étranglement 2, constitué par un papillon monté sur un axe 3 actionné par l'utilisateur,
• un venturi 4 au col duquel débouche un système de jaillissement principal d'un mélange air/combustible émulsionné, système alimenté par une cuve 6 à niveau constant contenant un flotteur 7 qui commande l'arrivée (non représentée) du combustible dans le cuve,
• un volet de départ excentré 9, placé à l'entrée d'air 8 du conduit d'admission 1.

In the two embodiments shown in FIGS. 1 and 2, where the corresponding members are designated by the same reference number, the carburetor comprises a housing made up of several assembled parts, delimiting an intake duct 1. We find, downstream upstream, in the intake duct 1:

• a throttling member 2, constituted by a butterfly mounted on an axis 3 actuated by the user,
• a venturi 4 at the neck of which opens a main spouting system of an air / emulsified fuel mixture, system fed by a tank 6 at constant level containing a float 7 which controls the arrival (not shown) of the fuel in the tank,
• an eccentric outlet flap 9, placed at the air inlet 8 of the intake duct 1.

The main throttling member 2 is associated with means not shown, which may be conventional, which regulate its minimum opening as a function of the temperature of the engine cooling water.

The main fuel spouting system 5 comprises a well 11 supplied with fuel from the tank 6, and a nozzle 12. The fuel taken from the well 11 by a tube 13 mixes with emulsion air from the air inlet 8 of the intake duct 1 through a calibrated orifice 14. A channel 15 receives the air-fuel mixture formed in the tube 13 and leads it to the spray orifice 15a located inside of a secondary venturi 16, placed at the neck of the venturi 4.

The starting flap 9 is mounted eccentrically on an axis 23 integral with a lever 10 terminated by a curved finger 10a. On this finger 10a is hung the end mobile 20a of a thermostatic member 20, such as a bimetallic spiral. The spiral 20 is contained in a housing (not shown) fixed on the body of the carburetor and its internal end is fixed on a boss of the housing; the spiral 20 can be brought to a temperature representative of that of the engine by conventional heating means, for example by circulating water for cooling the engine. It is designed to let the shutter close when it is cold and to drive the shutter gradually in the direction of opening when its temperature increases.

In the carburetor shown in Figure 1, the lever 10 has a unidirectional abutment connection with a rod 21. For this purpose, the lever 10 has a support plate 10b of the end 22, bent at right angles to the rod 21. The end 22 is kept at a constant distance from the axis 23 of the starting flap 9 by a lever 24 mounted idly on this axis 23.

The other end of the rod 21 is coupled to the membrane 25 of a pneumatic capsule 26. This membrane 25 is sandwiched between two cups 27 and 28 and divides the housing of the capsule 26 into two compartments 29 and 30. The compartment 29 is connected to the air inlet 8 of the intake duct and the compartment 30 is connected to the part of the intake duct 1 located downstream of the butterfly 2 by a pipe 31. A spring 32 placed in the housing of the capsule pushes the rod in the closing direction of the flap 9 and opposes the force created by the pressure difference acting on the membrane 25. A screw 33 for abutment of the rod 21 makes it possible to adjust the degree of opening partial of the starting flap 9 by the displacement of the membrane due to the vacuum prevailing in the duct 1 downstream of the butterfly 2.

According to the invention, the carburetor further comprises a movable stop 40 for partial forced opening of the flap 9. The stop 40 shown is constituted by the plunger of an electromagnet 41. This electromagnet 41 comprises a coil 42 and a fixed central core 43. When the coil 42 is traversed by no current, a spring 44 brings the stop in a rest position where a collar of the plunger 40 rests against a seat 45 on the frame of the electromagnet 41. The stop then prevents the flap 9 from closing beyond a predetermined position. In FIG. 1, the stop has been shown on the closing path of the butterfly, for greater clarity. In reality, the stop is placed on the path of a lever integral with the flap 9 and its axis 23.

When an electric current flows in the winding 42, the plunger 40 is drawn into an active position against the core 43, and releases the flap 9 which can take a fully closed position.

• la vitesse n du moteur (capteur 52),
• la fermeture du contact d'allumage (capteur 54),
• la température ϑ de l'eau de refroidissement (capteur 56).

The electric current for supplying the electromagnet 41 is supplied by a source not shown and controlled by a circuit 50 comprising a calculating member. The latter establishes or cuts the current as a function of the value of parameters representative of the state of the motor, supplied by sensors. They can in particular give an indication of:

• the speed n of the motor (sensor 52),
• closing the ignition contact (sensor 54),
• the temperature ϑ of the cooling water (sensor 56).

The calculation unit includes a clock. It will often be incorporated into a computer managing the engine's supply of air / fuel mixture at all speeds.

• le moteur froid a fonctionné pendant un intervalle de temps supérieur à une première valeur déterminée t0,
• l'intervalle de temps qui s'est écoulé depuis l'arrêt du moteur est inférieur à une autre valeur t1.

The computer is wired or programmed to supply the winding 42 of the electromagnet 41 when the ignition is closed while the engine is cold, unless the following conditions are simultaneously met:

• the cold engine has been running for a time interval greater than a first determined value t0,
• the time interval which has elapsed since the engine was stopped is less than another value t1.

This is a classic AND function.

To detect the first start-up of the engine for a duration greater than t0, it suffices that the calculation unit contains a counter accumulating the pulses supplied by the clock from the moment when the sensor 52 indicates that the engine is running at a speed higher than that at which the starter drives it until the engine stops, which can be detected either by returning to speed 0, or by switching off the ignition detected using of sensor 54. The counter has a determined capacity and emits an overflow signal / t0 if t0 is exceeded.

The second condition can be detected by providing in the calculation unit 50 a counter which increments at the rate of the clock after the engine has stopped and whose capacity corresponds to the duration t1, so that the overflow / t1 of the counter indicates that the duration t1 has been exceeded.

An additional condition to be fulfilled for the supply is advantageously the closing of the ignition contact, indicated by the sensor 54, so as not to unnecessarily consume current when the engine is at rest.

The temperature sensor is not essential; when the engine is hot, the movable stop 40 at rest does in fact duplicate the bimetallic spiral 20 and the fact that it is erased by coming into the active position is without disadvantage for operation. However, it is advantageous to use this movable stop only when necessary, that is to say when the temperature of the motor is less than a determined value and therefore cut the power supply to the electromagnet as soon as the motor warms up.

A possible sequence for activating the starting device which has just been described is as follows.

When the contact is closed while the motor has a temperature ϑ supplied by the sensor 56, which is lower than a set value, the electromagnet is energized, unless previously:

the engine has been running at a speed at least equal to the idle speed for a time greater than a value t0, then

did not operate for a period of time less than t1 (t1 can be constant, for example one hour). If these two conditions are not met, the mobile stop 40 is retracted and authorizes the complete closing of the starting flap 9.

As soon as the engine is started and turns on its own, the vacuum in the intake duct, transmitted through the pipe 31, partially opens the shutter 9 and decreases the richness to allow correct operation of the engine.

The calculating member 50 can be provided so as to no longer supply the electromagnet 41 as soon as the cooling temperature ϑ has reached a set value for which the bimetallic spiral has already half-opened the shutter, or as soon as the engine is running. itself at a speed at least equal to the idle speed. The movable stop then returns to its rest position shown in FIG. 1.

If, on the other hand, the cold engine has been stopped after short-term operation, for example one to three minutes, the temperature ϑ has not increased significantly and the bimetallic spiral does not exert a force capable of partially opening the shutter. In this case, during the following operation on the starter, the calculation member 50 does not supply the electromagnet 41. The movable stop 40 remains in the position shown in FIG. 1, prevents the shutter 9 from being completely closed and prevents stalling. of the engine by excess wealth.

• le moteur a été lancé alors qu'il est froid, c'est-à-dire que sa température est inférieure à une valeur prédéterminée,
• il a fonctionné pendant une durée supérieure à une première valeur de seuil.

In an alternative embodiment of the invention, the stop plunger 40 and the parts associated with it are omitted. However, in return, a solenoid valve 60, indicated in dashes in FIG. 1, is placed on the line 31 and is controlled by the circuit 50. If it is assumed that the solenoid valve 60 is of the closed type when it is supplied and opened at rest , the circuit 50 will supply a supply current to the solenoid valve 60 to close it when it has detected that the following conditions are met:

• the engine was started when it is cold, i.e. its temperature is below a predetermined value,
• it has operated for a duration greater than a first threshold value.

The circuit 50 will then include a time delay equal to the second threshold value mentioned above. The circuit can obviously be completed by means which inhibit the supply of the solenoid valve 60 as soon as the temperature of the engine has exceeded a determined value so as not to unnecessarily excite the solenoid valve after a new restart of the engine.

The operation of this embodiment appears immediately: when the cold engine is started when it has not operated for a long time, the pneumatic capsule 26 slightly opens the shutter 9 as soon as the start is effective.

As soon as the ignition is then switched off while the engine has been running for a period longer than the first threshold value, the circuit 50 supplies the solenoid valve 60 so as to maintain the vacuum existing in the chamber 30 of the capsule 26 and to prevent the shutter 9 from closing completely.

In the variant embodiment of the invention shown in FIG. 2, the carburetor does not include a pneumatic assistance capsule partially opening the starting flap 9. However, the calculating member 50 is programmed or wired so as to cause the coming of the movable stop 40 in its rest position as soon as the speed of the motor, supplied by the sensor 52, indicates that the motor is running by itself. In practice, as soon as the speed reaches, on a passenger vehicle engine, a speed of 600 revolutions / minute, it can be considered that the engine is autonomous. This solution has the advantage of a significant simplification.

The invention applies particularly well to the case of so-called "electronic" carburetors comprising a computer which can easily fulfill the function or the functions required by adding a few instructions or some electronic components, as well as the movable stop for example to a carburetor of the kind described in patent application FR 2 568 631.

Claims (4)

1. Carburator for internal combustion engine, comprising: a starting valve (9) biased toward closure by an element (20) which is responsive to the temperature of the engine when the temperature is lower than a limit value and toward opening by the airflow around it; first means having at least a first position in which they enable the valve to close completely and a second position in which they prevent the valve from closing beyond a determined position; and second means (50 or 60) responsive to at least the temperature of the engine for moving the first means, depending upon the conditions of operation of the engine, either to their first position or to their second position,
   characterized in that said first means comprise a movable electrically controlled stop member (40) for the starting valve (9), the first position being obtained when the electric control is energized and the second position, or rest position, when the electric control is de-energized and
   in that the second means comprise a computer unit (50) provided with at least a speed sensor and an ignition switch closure indicative sensor, delivering an electrical signal which brings the stop member into the first position thereof upon closure of the ignition switch and inhibiting the electric control for maintaining the first means in rest position upon starting of the engine in cold condition after an operating sequence of the cold engine for a duration which is higher than a first threshold value, followed with a stop of the engine for a duration lower than a second threshold value, the threshold values being controlled by the computer unit.
2. Carburator according to claim 1,
   characterized in that said computer unit (50) includes a clock and counters for measuring the duration of self-operation of the engine or the number of revolutions of the engine and the time duration after end of operation of the engine.
3. Carburator according to claim 1 or 2, characterized in that said second means are arranged for bringing back the stop member (40) into its rest position as soon as the speed of the engine exceeds a predetermined value, the carburator being devoid of pneumatic element for opening the starting valve responsive to occurence of a vacuum downstream of the user-actuated throttle member (2).
4. Carburator for internal combustion engine, comprising: a starting valve (9) biased toward closure by an element (20) which is responsive to the temperature of the engine when the temperature is lower than a limit value and toward opening by the airflow around it; first means having at least a first position in which they enable the valve to close completely and a second position in which they prevent the valve from closing beyond a determined position; and second means (50 or 60) responsive to at least the temperature of the engine for moving the first means, depending upon the conditions of operation of the engine, either to their first position or to their second position, said first means consisting of a pneumatic motor (26) for partially opening the starting valve and the second means comprising an electrically controlled valve (60) located on a line connecting the pneumatic element and that part of the induction passage (1) which is located downward of a driver controlled throttle member (2), responsive to temperature of the engine at least and characterized in that the electrically controlled value is closed when energized and open at rest and in that the second means (50, 60) comprise a computer unit (50) provided with at least a speed sensor and an ignition switch closure indicative sensor and feeding the electrically controlled valve for maintaining the first means in their second position upon occurence of an operating sequence of the cold engine for a duration which is higher than a first threshold value, followed with a new start of the cold engine after a stop of a duration lower than a second threshold value, said computer unit (50) dertermining the threshold values.

Images