EP0676543B1 - Two stage valve for air supply of injectors of internal combustion engines - Google Patents

Description

The invention relates to a two-stage valve for the air supply, on the one hand, of at least one injector air assisted for fuel injection into a intake manifold of a feed installation injection of an internal combustion engine, and, on the other hand, bypass on a throttle, such as a butterfly, movable in a conduit to regulate the feeding in air from the intake manifold.

In injection feed systems of internal combustion engines, in particular of the type multipoint, we know that, for each cylinder of an engine, at least one injector delivers fuel to the branch inlet manifold, directly in upstream of the corresponding intake valve (s), in the cylinder head of the engine. The air supply to the intake manifold, and therefore of the engine, is ensured and regulated by a throttle body, disposed between the air and the intake manifold, and traversed by at least one conduit in which a throttle member is rotatably mounted disc-shaped, called a butterfly, whose position in the duct varies between a full position opening and closing position more or less complete duct, depending on pedal position accelerator, as well as possibly some engine operating parameters.

To improve fuel spraying supplied by the injectors, we already know (EP-A-0 357 498) injectors with at least one passage in the nose fuel outlet, defining a mixing chamber connected to a supply of assistance air. he is also known (EP-A-0 409 170) that the additional air flow, delivered to each air-assisted injector be taken in upstream of the butterfly and controlled by a solenoid valve three-way idle, also serving as regulator idle.

In addition, there are known supply devices injection, the butterfly of which allows to close so practically completes the intake duct, the body of butterfly having an additional air duct, of which the entry is located upstream of the butterfly, and the exit in downstream of the latter, and in which the flow rate is adjustable by a solenoid valve. This solenoid valve is ordered in function of engine operating parameters, for example example the throttle opening and the engine speed for regulating the idle speed, the water temperature and the engine speed for cold start. We can thus reduce pollution by exhaust gases during cold start and slowdown phases high, and regulate the idle speed.

To ensure better spraying when the engine operates in modes other than full load, and in particular during activation at very low temperature (cold running), decelerating at high speed and during reduced loads, it has already been proposed, in the French patent application FR 92 13750 of November 16, 1992 on behalf of the applicant, that an additional air line, of which the entrance is located upstream of the butterfly and in which the flow rate is adjustable by a solenoid valve, brings the air having crossed the additional air solenoid valve to the mixture of each of the air-assisted injectors and a additional solenoid valve, opening downstream of the butterfly valve.

To avoid having to control two solenoid valves, which requires two actuators and complicates production of the control circuit, it has been proposed to use a two-stage valve, comprising a body in which a mobile equipment comprises first and second pistons, each of which is recalled by elastic means towards a waterproof application position or with minimal leakage against respectively a first and a second seat, for reduce at least the communication between at least an inlet of the body, supplied with air from upstream of the throttling organ, and one respectively of two exits from the body, a first of which feeds the air-assisted injectors, the second of which supplies the tubing downstream of the throttle, the crew mobile being movable by an actuator against elastic return means, for gradually putting each output in communication with the corresponding input, by moving the corresponding piston away from its corresponding seat.

But this realization has the disadvantage that the two pistons are integral with a member operated by a actuator, so that they are moved simultaneously by report to their respective headquarters, which does not allow control or regulate the air flow by one of the two valve outputs without simultaneously controlling and regulating the air flow through the other.

The needs of a regulated air supply additional, on the one hand, air-assisted injectors, and, on the other hand, bypass intake manifold on the butterfly, are not simultaneous.

The object of the invention is to remedy this drawback, and to propose a two-stage valve, of the type above, which better meets the requirements of the practice than known valves of this type.

To this end, the invention proposes a two-way valve stages which is characterized in that the first piston only is linked to the actuator and is integral in movement of first stop means which, beyond a first stroke of the first piston, from its position applied against the first seat, cooperate with second stop means, integral in movement with the second piston, to train it with the first piston on a second stroke, from the position of the second piston applied against the second seat.

It is thus understood that additional air can be sent to the air-assisted injectors by the first outlet, without additional air being admitted into the bypass intake manifold on the throttle, when engine operating conditions make it unnecessary this bypass power.

However, in the event of a cold start of the engine, or when decelerating at high speed, when the throttle is closed while a relatively large air flow must however be admitted to the engine, the drive second piston by the first, on the second commanded stroke by the actuator, ensures the required air flow.

Advantageously, the actuator regulates the air flow by the first exit to the assisted injector (s) by air, by regulating the position of the first piston on the first stroke, the air flow through the second outlet being kept low or zero, allowing regulation of the idle speed thanks to the air flow passing through the injector air assistance circuit under normal conditions idle.

Advantageously, the actuator regulates the air flow through the second outlet, downstream of the organ throttle or butterfly, regulating the position of the second piston on the second stroke, so, for example, to adapt this bypass air flow on the butterfly to a high speed deceleration strategy, or regulate this additional air flow depending on the temperature of the engine, during a cold start.

The input sections of the two circuits are sized to ensure that the air flow through the first output remains maximum when the pistons are moved to the second race.

In an advantageous embodiment, of structure simple and reliable, the actuator has a straight stroke and axially displaces an axis integral with the first piston, the second piston being annular, mounted to slide axially in the body and arranged substantially around the assembly constituted by the axis and the first piston, the assembly bearing the first stop means cooperating with the second stop means integral with the second piston.

Each piston can be moved into one respectively two axial chambers of the body, in each from which opens, for example radially, the outlet corresponding, and the corresponding seat is arranged, annular and axial, the axis crossing a bottom separating the two chambers in the extension of one another, and the axis carrying the stop means driving the second piston.

But this realization has the disadvantage of being bulky, especially axially, and demanding in terms of sealing.

For these reasons, in the embodiment preferred according to the invention, the first seat is delimited around the central passage of the second (annular) piston, side opposite the face of the latter coming into contact against the second seat, which surrounds a single air inlet in the body.

The second piston may have a tubular skirt, axially guided in a single axial chamber of the body, and in which the first piston is moved axially on at least part of the first race, the second stop means comprising at least one hook carried by the skirt and projecting towards the inside of the latter, and the first stop means comprising at least one lug in laterally projecting from the first piston and cooperating with or the hooks of the skirt, to train the second piston on the second stroke.

This two-stage valve construction with a single axial chamber in which the two are housed pistons, one of which is annular, facilitates the realization of the valve body, which may be at least partially, and of preferably completely, in one piece with the body in which is formed the conduit housing the throttling member mobile, and the single air inlet of the valve body can lead directly into the duct upstream of this organ strangulation.

In a simple and reliable way, the valve body can be closed, on the side opposite its single air intake, by a bottom crossed by the axis and supporting the actuator, and against which the elastic means of booster, advantageously comprising two helical springs, a first of which surrounds the axis and repels the first piston, and the second of which surrounds the first spring and pushes back the second piston.

In order to precisely regulate the axial position of the first piston on first stroke and axial position of the two pistons on the second stroke, and therefore to regulate precisely the air flows through the two outlets, the rectilinear actuator is advantageously a motor electric step by step.

Other characteristics and advantages of the invention will emerge from the description given below, at non-limiting title, of an exemplary embodiment described in reference to the single figure, which represents, partly in axial section and partly in side elevation, a set integrated two-stage butterfly valve body.

In the single figure, there is shown in 1 a body throttle, attached to an intake manifold 2, and crossed by a conduit 3, the inlet 4 of which is connected, by means not shown, at the outlet of an air filter, and whose outlet 5 opens into the tubing 2. The conduit 3 presents a zone 6 with an evolving section, in the form of portion of sphere delimited on one side by a lip 7 in protrusion from the middle part of the body 1 towards the inside of the conduit 3 and towards entry 4, that is to say upstream. A butterfly 8, forming a throttling member of the conduit 3 to the tubing 2, and in the form of a circular disc, is mounted on a diametrical axis 9 driven in rotation, by means not shown but classic, in part 6 of form evolution of the duct 3.

On one of its sides, the body 1 has a appendix 10, forming a valve body, in which is formed a cylindrical chamber 11, of axis A-A radial by relation to the axis B-B of the conduit 3. The chamber 11 communicates with this conduit 3 by a single axial inlet 12 (according to A-A), opening upstream of the base of the lip 7, and therefore in upstream of the butterfly 8, the circular section of the inlet 12 being less than the section of chamber 11. Entrance 12 is thus formed in a wall 13, separating the conduit 3 of chamber 11, and the side facing inward of the chamber 11 is arranged in an annular seat 14 and tapered, for a piston 15, itself annular and facing substantially frustoconical bearing against the seat 14. This piston 15 has a central passage 16, opposite entrance 12, and extends, on the side opposite this entrance 12, by a cylindrical skirt 17 having a range 18 by which the piston 15 is slidably mounted along the axis A-A and guided axially in chamber 11. On the side opposite the frustoconical head of the piston 15, the skirt 17 extends axially by at least one pair of hooks 19, diametrically opposite, each with a projecting tooth radial with respect to the axis A-A and towards the interior of the skirt 17. The piston 15 is resiliently pushed axially (according to A-A) so that its frustoconical external face is applied against the frustoconical seat 14 by a spring helical 20 resting, on the one hand, against the bearing surface 18, between the hooks 19 and the wall of the chamber 11, and, on the other hand, against a bottom 21 closing with a leak minimal, thanks to the seal 22, the chamber 11 on the side opposite to input 12, and supporting an actuator 23 with stroke straight formed by an electric stepper motor axially moving an axis 24, which crosses the bottom 21, and whose end inside chamber 11 carries another piston 25. The piston 25 is not annular, but has also a head 26 with a substantially frustoconical external face, by which it bears against another seat 27 annular and frustoconical, delimited on the internal face of the piston 15 around its central passage 16, under the thrust elastic return of another helical spring of compression 28 also bearing, on one side, against the bottom 21, and on the other, against the piston 25, between the axis 24 that this spring 28 surrounds, and an axial and tubular skirt 29 carried by the piston 25, to guide the spring 28 and prevent any interference of the latter's turns with the hooks 19 of the piston 15. The piston 25 also carries, projecting radially outwards, lugs 30, forming mechanical stop, and intended to cooperate with the hooks 19, also forming a mechanical drive stop, of the as described below.

Finally, two air outlet channels 31 and 32 are formed in the body 10 and open radially (by in relation to axis A-A) in chamber 11, the first, 31, between the bottom 21 and the pistons 15 and 25, and the second, 32, opposite the skirt 17 of the piston 15, between the bearing surface 18 and the seat 14 of the chamber 11. This second outlet channel 32 is extended by a channel 33 formed in the pipe 2 and opening into the extension of the intake duct 3, downstream of the butterfly 8.

The two-stage valve thus produced is compact and balanced structure: it includes a unique chamber 11 with a single inlet 12, two pistons 15 and 25 one of which, 15, slides axially in the chamber 11, and the other, 25, is moved axially in the piston 15, by tubular structure, by movement of the maneuvered axis 24 by the actuator 23. The return springs 20 and 28 are coaxial and recall pistons 15 and 25 in their initial position, which is that shown in the figure unique. In this initial position, under the effect of spring 28, the internal piston 25 closes the central passage 16 by pressing against the seat 27 of the piston 15, and the latter closes entrance 12 by application against seat 14 under the effect of spring 20.

The air flow through the outlet channels 31 and 32 is therefore very weak or zero.

In operation, the stepping motor 23 regulates the axial position of the piston 25 by moving its head 26 away from the seat 27 internal to the other piston 15, on a first stroke axial defined by the axial distance between the pins 30 of the piston 25 and the teeth projecting from the hooks 19 of the piston 15. By regulating the displacement of the piston 25 on this first axial stroke, we regulate the air flow through entrance 12 and passage 16 then between seat 27 and piston 25, to flow through the first outlet channel 31, connected to the air-assisted injectors. We regulate the assistance air flow from the injectors, which allows regulate the idling speed, under normal conditions engine temperature, up to a flow rate of around 20 kg / h when the piston 25 has run the entire first axial stroke. This first race can be by example of 2 mm and obtained for 50 steps of motor rotation step by step 23.

In case of additional air demand, in particular during a cold start of the engine, or during deceleration at high speed, the stepper motor 23 drives by the axis 24 the piston 25 on a second axial stroke, on which the pins 30 of the piston 25 are in mechanical abutment against the hooks 19 of the skirt 17 and thus cause the piston 15, which is moved away from seat 14, so that air goes through the opening 12 then between the seat 14 and the piston 15, and through the outlet duct 32, to lead into the channel 33 and the branch 2 in bypass on the butterfly 8, closed under these operating conditions. We can thus allow an additional air flow of up to 60 kg / h approximately, when pistons 25 and 15 have been moved on a second axial stroke of the order of 6 mm, obtained for an additional movement of 150 steps from the step motor at step 23.

The two-stage valve, thus integrated into the body of butterfly 1, allows to regulate, between the first and the fiftieth step of motor 23, the flow passing through the outlet 31 to the air-assisted injectors, and, between the fifty-first and two hundredth steps, lets regulate the air flow through outlet 32, bypass on the butterfly 8, while the air flow through the outlet 31 to the air-assisted injectors is kept maximum.

As soon as the electric stepper motor 23 is no longer energized, the return springs 20 and 28 push the pistons 15 and 25 against seats 14 and 27 in position for closing entrance 12 and central passage 16, which cut communications between input 12 and outputs 32 and 31.

The two-stage valve thus produced is simple and reliable, with little or no friction, as well as low risk of clogging of the air passages. She is also very easy to fly.

Claims (10)

1. A two-stage valve firstly for feeding air to at least one air-assisted injector for injecting fuel into an inlet manifold (2) of a fuel injection system for an internal combustion engine, and secondly, for bypassing a throttle device (8) such as a butterfly valve which is movable in a duct (3), for regulating the air supply to the inlet manifold (2), the valve comprising a body (10) in which a movable assembly comprises first and second pistons (15, 20), each of which is returned by resilient means (20, 28) towards a position of application, with minimal leakage, against first (14) and second (27) seats respectively, in order to reduce to its minimum value communication between at least one inlet (12) in the body (10) which is fed with air from upstream from the throttle member (8), and respective ones of two outlets (31, 32) from the body, a first of which (31) feeds the air-assisted injector(s) and the second of which (32) feeds the manifold (2) downstream from the throttle member (8), the movable assembly being movable by an actuator (23) against the action of the resilient return means (20, 28), in order to place each outlet (31, 32) in communication with the corresponding inlet (12) by spacing the corresponding piston (15, 25) from its corresponding seat (14, 27), only the first piston (25) being connected to the actuator (23) and moving integrally with first stop means (30) which, after a first stroke of the first piston (25) from its position of application to the first seat (27), cooperate with second stop means (19) which move integrally with the second piston (15), so as to entrain this with the first piston (25) over a second stroke, from the position of application of the second piston (15) to the second seat (14).
2. A valve according to claim 1, characterized in that the actuator (23) regulates the airflow through the first outlet (31) to the air-assisted injector(s) by regulating the position of the first piston (25) over the first stroke.
3. A valve according to claim 1 or 2, characterized in that the actuator (23) regulates the airflow through the second outlet (32) to downstream from the throttle member (8) by regulating the position of the second piston (15) over the second stroke.
4. A valve according to any one of claims 1 to 3, characterized in that the airflow through the first outlet (31) to the air-assisted injector(s) remains at its maximum while the pistons (15, 25) are displaced over the second stroke.
5. A valve according to any one of claims 1 to 4, characterized in that the actuator (23) acts linearly and axially displaces (A-A) a rod (24) integral with the first piston (25), the second piston (15) being annular and mounted to slide axially in the body (10) and being disposed substantially around the assembly formed by the rod (24) and the first piston (25), said assembly carrying the first stop means (30) which cooperate with the second stop means (19) integral with the second piston (15).
6. A valve according to claim 5, characterized in that the first seat (27) is defined around the central passage (16) of the second piston (15), opposite the face of the latter which comes into contact with the second seat (14), which surrounds a single air inlet (12) in the body (10).
7. A valve according to claim 6, characterized in that the second piston (15) has a tubular skirt (17) guided (18) axially (A-A) in a single axial chamber (11) of the body (10), and in which the first piston (25) is moved axially over at least part of the first stroke, the second stop means comprising at least one hook (19) carried by the skirt (17) and projecting therein, the first stop means comprising at least one lug (30) projecting laterally from the first piston (25) and cooperating with the hook(s) (19) of the skirt (17).
8. A valve according to claim 6 or 7, characterized in that its body (10) is at least partially in one piece with a body (1) in which is formed the duct (3) which houses the movable throttle member (8), and the single air inlet (12) of the valve body (10) opens directly into the duct (3) upstream from said throttle member (8).
9. A valve according to claim 8, characterized in that the body (10) of the valve is closed on the side opposite to its single air inlet (12) by a partition wall (21) through which the rod (24) passes and which supports the actuator (23) and against which abut the resilient return means comprising two helical springs (20, 28), of which the first surrounds the rod (24) and biases the first piston (25) and of which the second (20) surrounds the first (28) and biases the second piston (15).
10. A valve according to any one of claims 1 to 9, characterized in that the actuator (23) comprises an electric stepper motor.

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