EP0604285A1 - Electrically actuated canistercircuit regeneration valve - Google Patents

Abstract

The valve has its shutter (19) bound in terms of movement to the plunger (20) of a solenoid (21) for opening the shutter, and to the membrane (12) pushed by a return spring (22) towards closure of the shutter onto the outlet (18) connected to the intake pipe of the engine. The chamber (14) of the shutter (19) is connected to the canister through the fixed calibration device (17). The chamber (13) on the other side of the membrane (12) is at atmospheric pressure or the pressure of the canister. The partial vacuum which acts on the calibration device (17) is applied to the membrane (12) which is also subjected to the effects of the spring (22) and of the solenoid (20-21). The regeneration flow rate of the canister through the calibration device (17) is thus modulated continuously by means of a variable partial vacuum piloted by the modulation in mean current of the solenoid control. Application of the proportional valve with continuous flow rate for the regeneration of internal combustion engine canisters. <IMAGE>

Description

The invention relates to a valve with electrical control of a canister regeneration circuit, for an internal combustion engine supplied with air or with carburetted air by at least one intake duct in which the flow is controlled by a shutter, for example of the type rotary.

More specifically, the invention relates to a proportional valve with continuous flow, controlled by an electrical setpoint signal, for a canister regeneration circuit associated with an internal combustion engine, the fuel supply installation of which can either include a carburetor, including the rotary shutter, or throttle valve, controls the flow of carburetted air or air-fuel mixture, or be of the so-called "injection" type and comprise a throttle body, including the rotary shutter controls the intake air flow.

In order for motor vehicles to meet the current anti-pollution standards relating to the emission of fuel or combustible vapors, whether the internal combustion engine with which they are equipped is in operation or stopped, it is known to collect in a receptacle called canister fuel vapors from various organs containing or traversed by fuel, in the circuit followed by the latter in the vehicle and its engine. On vehicles fitted with an injection fuel supply system, fuel vapors come in particular from the fuel tank. However, in general, fuel vapors can also come from the engine, the injection pipes and the injectors, or, where appropriate, from the carburetor.

To avoid their rejection in the ambient air, these fuel vapors are collected by a recovery line, which brings them to the canister, produced under the form of a receptacle containing means for absorbing these fuel vapors, for example a charge of activated carbon, fulfilling the role of a sponge and a filter with respect to the vapor fuel which reaches the canister . The latter is provided with a vent in communication with the atmosphere, so that the fuel tank is vented through the canister.

To prevent the canister from rejecting fuel in the open air through its vent, when it is saturated with fuel, it is known to regenerate it cyclically. To this end, it is known to use a canister regeneration circuit, which purges the fuel from time to time of the fuel it has absorbed, and transmits this fuel to the engine. The canister regeneration circuit includes a pipe connecting the canister to the intake pipe, downstream of the rotary shutter, and a valve mounted on this pipe. When the valve is open, the vacuum prevailing downstream of the rotary shutter in the intake duct causes in the pipe and in the canister a suction of ambient air through the canister vent, and this ambient air sucked in thus purges the canister of the fuel it contains and mixes with this fuel to be sucked with it downstream of the rotary shutter in the intake duct. We understand that the arrival of this fuel air changes the richness of the air-fuel mixture prepared by appropriate engine parts (carburetor or injector as appropriate) receiving control commands developed from signals from different parameter sensors of engine operation, and in particular of a so-called λ probe, or probe measuring the oxygen level in the exhaust gases.

In order to eliminate this perturbation of the richness, it has already been proposed that the valve of the regeneration circuit is an electrically controlled valve ensuring a modulation of the regeneration flow of the canister, which flow is difficult to know, because the fuel load collected in the canisters cannot be known with precision and depends on many parameters, such as the ambient temperature, whether or not resulting from the operation of the engine, the temperature and conditions for filling the fuel tank, etc.

To this end, the electrically operated valves usually used are valves comprising a calibrator with a constant passage section, and a flow control valve in the regeneration pipe, this valve being linked in movement to a core of a solenoid, the coil of which is supplied by an electric current for controlling the position of the valve.

In these traditional type valves, the variation of the flow rate is obtained by modulating the cross section of the calibration subjected to the vacuum of the motor, this modulation being ensured by the valve which is that of a solenoid valve, that is to say a electromagnetic valve operating in all-or-nothing mode, but the solenoid coil of which is supplied with electric current with rectangular slots with variable opening duty cycle. That is to say that the opening time, for a constant period, corresponds to a variable fraction of this period, corresponding to the length of the current time slot used.

For an engine running at 3000 rpm for example, a half turn is covered in 10 ms.

In the embodiments of the state of the art, low frequency solenoid valves excited at constant frequencies ranging from 5 to 20 Hz have been used. These frequencies correspond to constant periods ranging from 200 to 50 ms. If the opening duty cycle is 10%, this results in a length of the rectangular slot of corresponding current, and therefore substantially a duration of opening of the valve ranging from 20 to 5 ms. As a result, the duration of opening of the solenoid valve, and therefore the duration of aspiration of the canister regeneration fuel in the intake duct, extends from approximately a quarter to approximately three quarter turns of the engine. The consequence is that this regeneration fuel cannot be allowed in all the engine cylinders.

The use of low frequency solenoid valves for the regeneration of canisters therefore has the drawback of causing an imbalance in the supply of the engine cylinders.

To overcome this drawback, it has been envisaged to use high-frequency solenoid valves, but their rapid wear linked to their high operating frequency, and their high cost have caused them to be excluded.

By the invention, it is proposed to remedy these drawbacks, and an object of the invention is to provide an electrically controlled valve making it possible to spread the regeneration flow so that all the cylinders of the engine receive substantially the same fraction. canister regeneration fuel.

Another object of the invention is to propose an electrically controlled valve making it possible to ensure a regenerative flow rate of the canister which is continuous, but modulated and slaved to an electrical setpoint signal, so as to obtain a valve with flow rate proportional to this instruction.

The idea underlying the invention consists in modulating the regeneration flow rate of the canister by passing this flow rate through a calibrator with a constant passage section, but which is subjected to a modulated vacuum, unlike the solenoid valves of the 'state of the art, in which we modulate the effective section of the calibration subjected to engine vacuum.

To this end, the electrically controlled valve according to the invention, for a canister regeneration circuit of the type presented above, comprising a pipe connecting the canister to the intake duct, downstream of the shutter, and on which is mounted the valve which comprises a calibrator with constant passage section, a flow control valve in the pipeline and which is linked in movement to a core of a solenoid whose coil is supplied by an electric current to control the force on the valve, is characterized in that the valve is integral in movement with a flexible membrane, which delimits in a housing two chambers, one of which is maintained at a pressure close to or equal to atmospheric pressure, and the second of which is a modulated vacuum chamber, containing the valve and placed in communication, by an inlet orifice, with the canister by through said calibrator, and through an outlet orifice with the intake duct, the membrane thus subjected to a depression close to or equal to that which acts on the calibrator also being subjected to the opposing forces of elastic means, which tend to close the valve on the outlet, and the solenoid, the coil of which creates a force having the effect of moving the valve from the outlet to open the latter, when is traversed by a variable average current constituting an electrical reference signal fixing the force on the valve.

It is understood that in operation, the membrane is in equilibrium under the combined actions of depression, which determines the flow, elastic means, which tend to return the valve in the closed position, and of the force due to the solenoid, and therefore current flowing through its coil. A relationship is thus established between the vacuum, and therefore the flow, on the one hand, and, on the other hand, the average electric current which flows through the solenoid coil. This valve thus makes it possible to modulate the regeneration flow continuously by means of a variable vacuum determined using an average control current.

Advantageously, the variable mean control current is obtained by supplying the solenoid coil with rectangular electrical current slots with variable duty cycle.

For an engine powered by a carburetor controlled by a computer, or powered by an installation injection controlled by an engine control system, the variable mean control current will advantageously be controlled by a control member sensitive to at least one signal from at least one sensor of an engine operating parameter, such as a richness sensor of the air-fuel mixture, this control member being the carburetor control computer or the engine control system computer.

The valve can be linked in movement to the core of the solenoid by means of reduction of the amplitude of the movement of the valve relative to the amplitude of the movement of the core, in order to best adapt each of these movements to practical needs. However, in order to reduce the cost of producing the valve as well as its size, it is advantageous that, according to a simplified structure, the valve be directly integral in movement with the core of the solenoid, the valve and the core being arranged on either side. other of the membrane.

In a preferred embodiment, the valve is in one piece with the core, which extends partially in the first chamber, and the elastic means comprise at least one return spring, housed in this first chamber, and produced under the shape of a helical spring partially surrounding, and preferably substantially coaxially the core. This gives better guidance of the valve-core assembly in its displacements along its longitudinal axis, which is also that of the helical spring and advantageously of the solenoid coil, as well as more balanced stresses on the membrane.

The first chamber can be maintained at atmospheric pressure or at canister pressure, which is little different from atmospheric pressure. In this second case, the first chamber is in communication with the canister by an inlet orifice and has an outlet orifice in communication with the inlet orifice of the second chamber through the calibrator.

A continuous flow valve modulated by the modulation of the average control current passing through the solenoid coil is thus obtained, the valve being compact and easy to assemble, since it suffices to connect the inlet orifice of its first chamber to the canister and the outlet of its second chamber to the intake duct, and to ensure the electrical supply of the solenoid by the control current.

• la figure 1 représente schématiquement un circuit de régénération de canister, comprenant la vanne selon l'invention, et monté entre un canister et un conduit d'admission d'un carburateur ou corps de papillon de moteur à combustion interne,
• la figure 2 est une vue schématique en coupe d'un premier exemple de vanne, et
• la figure 3 est une vue analogue à la figure 2 d'un second exemple de vanne.

Other advantages and characteristics of the invention will emerge from the description given below, without implied limitation, of exemplary embodiments described with reference to the appended drawings in which:

• FIG. 1 schematically represents a canister regeneration circuit, comprising the valve according to the invention, and mounted between a canister and an intake duct of a carburetor or throttle body of an internal combustion engine,
• FIG. 2 is a schematic sectional view of a first example of a valve, and
• Figure 3 is a view similar to Figure 2 of a second example of a valve.

In FIG. 1, the canister 1, with an internal volume generally substantially equal to the engine displacement, contains an absorbent or adsorbent load 2, for example of activated carbon, which takes charge of the fuel vapors, coming in particular from the tank of fuel, and which are brought to the canister 1 by the recovery line 3. The canister 1 can thus contain for example 100 g of fuel. It is provided with a vent 4 connecting it to the atmosphere, and is also connected to the intake duct 5 of a carburetor body or of a throttle body of an internal combustion engine, downstream of the '' rotary shutter or throttle valve 6, the angular position of which in the intake duct 5 is controlled to regulate the air intake rate, in the case of a throttle body, or of air carburetor in the case of a carburetor. This connection of the canister 1 to the intake duct 5 is ensured by a circuit 7 for regenerating the canister 1, this circuit 7 comprising a regeneration line 8 opening, at its entry into the canister 1 and, at its exit, into the intake duct 5, as well as an electrically controlled valve 9, connected between the upstream 8a and downstream 8b branches of the pipe 8. The valve 9, two embodiments of which are shown in FIGS. 2 and 3, is a check valve whose position is controlled by a solenoid receiving its electric control current from a control device schematically represented at 10. When the valve 9 is open, the vacuum prevailing in the intake duct 5 downstream of the butterfly valve 6 causes, through the pipe 8 and the canister 1, an aspiration of ambient air by the vent 4, and this air sucked through the charge 2 drives the fuel retained by the latter in the ad duct mission.

In the example of FIG. 2, the valve 9 comprises a body or housing 11 the interior of which is subdivided by a flexible waterproof membrane 12 which can be deformed into two chambers 13 and 14, the first of which 13 is maintained at atmospheric pressure. The second chamber 14 has an inlet 15 connected to the upstream part 8a of the pipeline 8 for regenerating the canister 1 by a tubular nozzle 16 containing a calibrator 17 or restriction, with a constant passage section. The second chamber 14 also has an outlet orifice 18 connected to the downstream part 8b of the regeneration pipe 8, and the periphery of the outlet orifice 18 constitutes a seat for the conical head of a valve 19. This valve 19 , with a cylindrical body, is in one piece with the core 20, also cylindrical, of a solenoid comprising an excitation coil 21 mounted on the body 11, outside the first chamber 13, on the side opposite to the outlet orifice 18. The monobloc assembly of the valve 19 and of the core 20 is integral with the membrane 12, of which it crosses the central part with sealing. The valve 19 is thus supported by the membrane 12 in the second chamber 14, while the core 20, on the other side of the membrane 12, extends partly in the first chamber 13 and partly outside of the latter, in the coil 21. The part of the core 20 located in the chamber 13 is surrounded by a helical return spring 22 bearing on the housing 11 and on the membrane 12 to tend to push it in the direction applying the valve 19 to its seat, so as to close the outlet 18 when the coil 21 is not supplied. The housing 11, the membrane 12, the one-piece valve 19-core assembly 20, the coil 21 and the outlet orifice 18 are, to ensure better mechanical behavior of the valve assembly 19-core 20, preferably coaxial with the longitudinal axis of this assembly.

In operation, the coil 21 is traversed by an average electric control current, which results from the supply of rectangular slots of current with variable duty cycle. The valve assembly 19-core 20 is then subjected to an electromagnetic force Fm which separates the valve 19 from the outlet orifice 18, against the spring 22. The chamber 14 is then in communication via the outlet 18 with the intake duct 5 and, through the calibrator 17, with the upstream pipe 8a and the canister 1. The control pressure Pc in the chamber 14 is then intermediate between the pressure of the canister Pcan, upstream of the calibrator 17, it- same close to atmospheric pressure Pa in chamber 13, and pressure in the intake duct 5, downstream of the butterfly valve 6. For a given average control current, and therefore a given position of the membrane 12, of the valve 19 and from the core 20, it is understood that if the butterfly 6 is moved in the closing direction, the vacuum in the intake duct 5 increases downstream of the butterfly 6. The control pressure Pc tends to decrease, and the differential pressure acting on the membrane 12 increases, so that the valve 19 is brought closer to the outlet orifice 18. As the passage section decreases, the control pressure Pc downstream of the calibrator 17 increases, so that the differential pressure exerted on the membrane 12 tends to return to its initial value, and to recall the membrane 12, the valve 19 and the core 20 in their given initial position. The operation is similar when the butterfly 6 is operated in the opening direction. The valve thus functions as a self-correcting regulator.

In operation, the membrane 12 is subjected to the return force Fr of the spring 22, which tends to close the valve 19 on the outlet 18, to an electromagnetic force Fm exerted on the core 20 by the field created by the coil 21, and to the force resulting from the application, on the effective surface S of the membrane 12, of the differential pressure between the atmospheric pressure Pa in the chamber 13 and the control pressure Pc in the chamber 14. In operation, the membrane 12 is in equilibrium under the action of these three forces, according to the following formula (1): $$\text{(1) S (Pa - Pc) = Fm - Fr}$$

où
Sc est la section de passage constante du calibreur 17,
ρ la masse volumique du mélange air-combustible provenant du canister 1, et
Pcan et Pc sont respectivement la pression dans le canister ou en amont du calibreur 17, et la pression de commande dans la chambre 14.Simultaneously, the regeneration rate Q passing through the calibrator 17 is given by the known formula (2) below: $$\text{(2) Q = Sc x [2 ρ (Pcan - Pc)],}$$

or
Sc is the constant passage section of the calibrator 17,
ρ the density of the air-fuel mixture from canister 1, and
Pcan and Pc are respectively the pressure in the canister or upstream of the calibrator 17, and the control pressure in the chamber 14.

Since Pa and Pcan are close to each other, we can, in formula (2), replace Pcan - Pc by the value of Pa - Pc in formula (1), ie Fm - Fr.
We obtain that the flow rate Q is given by formula (3): $$\text{(3) Q = Sc x [2 ρ (Fm - Fr)]}$$

It can be seen that the regeneration flow rate Q is independent of Pcan, continuous and modulated by the modulation of the electromagnetic force Fm, itself a function of the mean control current of the coil 21. The valve is thus of continuous and proportional flow, subject to an electrical current setpoint. In order for this valve to be relatively insensitive to engine vibrations, a spring 22 with a low force threshold, but sufficient for this purpose, is chosen.

The example of a valve in FIG. 3 is essentially distinguished from that of FIG. 2 only by the following differences: the housing 11 ′ has a lateral passage 23, connecting the two chambers 13 and 14 to each other, and in which the calibrator 17 is mounted. The upstream part 8a of the regeneration pipe is no longer connected to the chamber 14 through the calibrator 17, but to an inlet orifice 24 of the chamber 13, having an orifice for outlet 25 in communication with the inlet orifice 15 of the chamber 14 via the calibrator 17. Thus the chamber 13 is no longer maintained at atmospheric pressure but directly at the pressure of the canister Pcan. For the rest, there is the solenoid with coil 21 and plunger 20 in one piece with the valve 19 and integral in movement with the membrane 12 urged in the direction of closing of the valve 19 on the outlet orifice 18 of the chamber 14 by the return spring 22.

In this example, the differential pressure or vacuum Pcan - Pc which acts on the calibrator 17 is applied directly to the membrane 12, also subjected to the forces Fr of the spring and Fm of the solenoid, as defined above. Formulas (1) to (3) given above apply by replacing Pa with Pcan in formula (1). This valve therefore provides the same advantages as that of the FIG. 2 and makes it possible to modulate the regeneration flow rate continuously, by means of a variable depression, determined by the modulation of an average electric control current.

This electric current is supplied for example by a control computer of a carburetor or a computer of an engine control system, and developed from information coming in particular from a richness probe, of the λ probe type, detecting the oxygen content in engine exhaust.

Claims (10)

Valve with electrical control of the canister regeneration circuit (7) (1), for an internal combustion engine supplied with air or carburetted air by at least one intake duct (5) in which the flow is controlled by a shutter ( 6), the canister (1) containing means (2) for absorbing the fuel vapors brought into the canister by a recovery pipe (3) and being provided with a vent (4) in communication with the atmosphere, and the canister regeneration circuit (7) (1) comprising a pipe (8) connecting the canister (1) to the intake duct (5), downstream of the shutter (6), and the valve (9) mounted on the pipeline (8), said valve comprising a calibrator (17) with constant passage section, a valve (19) for controlling the flow in the pipeline (8), and which is connected in movement to a core (20) a solenoid whose coil (21) is supplied by an electric current to control the force on the valve,
characterized in that said valve (19) is integral in movement with a flexible membrane (12), which delimits in a housing (11, 11 ') two chambers (13, 14), of which a first (13) is held at a pressure close to or equal to atmospheric pressure, and the second of which (14) is a modulated vacuum chamber, enclosing the valve (19) and placed in communication, by an inlet orifice (15), with the canister ( 1) by means of said calibrator (17), and by an outlet orifice (18) with the intake duct (5), the membrane (12) thus subjected to a depression close to or equal to that which acts on the calibrator (17) also being subjected to the opposing forces of elastic means (22), which tend to close the valve (19) on the outlet orifice (18), and of the solenoid (20-21), including the coil ( 21) creates a force having the effect of drawing aside the valve (19) from the outlet orifice (18) to open the latter, when it is traversed by a coura nt variable means constituting an electrical reference signal fixing the force on the valve (19). Valve according to claim 1, characterized in that the valve (19) is linked in movement to the core (20) of the solenoid by means of reduction of the amplitude of movement of the valve relative to the amplitude of movement of said core. Valve according to claim 1, characterized in that said valve (19) is directly integral in movement with said core (20) of the solenoid, the valve and the core being arranged on either side of the membrane (12). Valve according to claim 3, characterized in that said valve (19) is in one piece with said core (20), which extends at least partially in said first chamber (13). Valve according to any one of Claims 1 to 4, characterized in that the said elastic means comprise at least one return spring (22) housed in the said first chamber (13). Valve according to claim 5, as attached to claim 4, characterized in that said return spring (22) is a helical spring which partially and substantially coaxially surrounds said core (20). Valve according to any one of Claims 1 to 6, characterized in that the said first chamber (13) is maintained at atmospheric pressure. Valve according to any one of Claims 1 to 6, characterized in that the said first chamber (13) is maintained at the pressure of the canister (1), with which it is in communication by an inlet orifice (24), and has an outlet (25) in communication with the inlet (15) of the second chamber (14) via said calibrator (17). Valve according to any one of Claims 1 to 8, characterized in that the said variable mean current is obtained by supplying the solenoid coil (20) with rectangular electrical current slots with ratio variable cyclic. Valve according to any one of Claims 1 to 9, characterized in that the said variable mean current is controlled by a control member (10) sensitive to at least one signal coming from at least one sensor of an operating parameter of the engine, such as an air-fuel mixture richness sensor.

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