EP0918925B1 - Valve for an internal combustion engine exhaust gas recirculation system - Google Patents

Abstract

A valve for controlling the amount of exhaust gas recycled in an internal combustion engine exhaust gas recirculation system is disclosed. The valve comprises a sealing member (2; 14; 32) arranged in a duct (3; 10, 11; 35, 38) for substantially sealingly engaging, in the closed position, an abutment member (5; 13; 33), and rotary actuating means for moving said sealing member from the closed position to an open position. Said rotary actuating means comprise a stator and a rotor of which one is provided with at least one magnet while the other is provided with at least one control winding, said stator and said rotor being mounted in such a way that when no current is flowing through the control winding, the sealing member is urged against the abutment member by residual magnetic forces.

Description

The present invention relates to a quantity control valve exhaust gas recycled into a gas recirculation system exhaust from an internal combustion engine.

We already know exhaust gas recirculation systems (EGR) intended, in internal combustion engines, to recycle part exhaust gases on admission to the cylinders. Such recycling of gases, generally inert, and therefore not participating in combustion, lowers the combustion temperature, which has the effect of reduce the level of nitrogen oxides (NOx) present in gases exhaust, and therefore to limit the pollution caused by such engine.

However, for the engine to operate satisfactorily, a such recirculation should only occur under conditions of normal engine operation and therefore be discontinued in all non-nominal circumstances, i.e., essentially, cold, under heavy load, at idle and at high speed. In these latter cases, no recirculation is allowed while, in normal operation, the recirculation of up to 25% by weight of the admitted gases is permitted. A regulation is therefore necessary.

Until now, this regulation has been obtained by arranging in the recirculation circuit a needle valve in which the position of this the latter was controlled by a membrane subjected to a low pressure or less important. The source of vacuum was in the tubing intake or resulted from a vacuum pump, a solenoid valve being disposed between this tubing and the needle valve and membrane. The solenoid itself was supplied with alternating current, whose ratio cyclic was determined by a computer to which the input was supplied, the coolant temperature, charge and rotational speed of the motor.

These devices have drawbacks associated with backpressures cyclical prevailing downstream of the needle valve and tending to open the latter. It is therefore necessary to apply the needle on its seat by elastic means exerting a relatively large force, which should be win when you want to open the valve.

It has also been proposed to use a valve of the type comprising a disc. mobile in rotation and provided with a light cooperating with a fixed orifice, and motor means for driving this disk in rotation, in particular a step-by-step engine.

Although generally satisfactory, these valves have the disadvantage that the disc and its seat must be made of ceramic. They are therefore relatively expensive, as is the engine they use.

WO 88/07625 also discloses a valve conforming to preamble of claim 1. But in this valve, the shutter member is permanently under the control of the actuating means.

The present invention aims to overcome these drawbacks.

To this end, the invention relates to a valve according to claim 1.

The effort of applying one organ to the other is therefore provided at least partially or entirely by the magnet.

In a first embodiment, the shutter member is driven directly by said rotary actuating means.

In this case, the shutter member can be a flap mounted in said duct. on the axis of rotation of the rotary actuating means.

More particularly, the walls of said conduit can form two shoulders of opposite directions on either side of the axis of the flap, said shoulders forming stop members and cooperating with the edges of the flap to provide sealing.

In another embodiment, the shutter member is driven by said rotary actuating means via a cam.

This embodiment has the advantage that one can choose as desired the stroke of the shutter member as a function of that actuation means.

In this embodiment, the shutter member can be a valve arranged to be driven in translation by said means rotary actuation through said cam.

Said cam may comprise a first part which is substantially cylindrical secured to the shutter member and blocked in rotation, on which are formed helical grooves arranged to cooperate with balls arranged in cells of a second piece integral with rotary actuation means and locked in translation.

Said cam can also be formed at the end of a mounted lever on the axis of rotation of the drive means and cooperates with a shoulder of the valve stem.

In another embodiment, said cam comprises a first part secured to the rotary actuating means, on which are formed by helical grooves arranged to cooperate with rollers mounted on a second part locked in rotation and secured to the member shutter.

According to yet another embodiment, the valve according to the invention includes a helical ramp coaxial with the output shaft of the means rotary actuation and driven in rotation by said means actuator, arranged to cooperate with a cam follower roller likely to cause the shutter member.

• la figure 1 est une vue en perspective d'une vanne selon un premier mode de réalisation de l'invention ;
• la figure 2 est une autre vue en perspective, en coupe, de la vanne de la figure 1 ;
• la figure 3 est une vue en perspective éclatée d'une vanne selon un deuxième mode de réalisation de l'invention ;
• la figure 4 est une vue en coupe axiale de la vanne de la figure 3 ;
• la figure 5 est une vue en perspective, en coupe, d'une vanne selon un troisième mode de réalisation de l'invention ;
• la figure 6 est une vue en coupe axiale de la vanne de la figure 5, montée sur un support de montage;
• la figure 7 est un graphique illustrant le fonctionnement de l'invention.
• la figure 8 est une vue en perspective éclatée d'une vanne selon un autre mode de réalisation de l'invention;
• la figure 9 est une vue en coupe axiale de la vanne de la figure 8;
• la figure 10 est une vue en perspective éclatée d'une vanne selon encore un autre mode de réalisation de l'invention;
• la figure 11 est une vue en coupe axiale de la vanne de la figure 10; et
• la figure 12 est une vue en coupe axiale d'une vanne selon encore un autre mode de réalisation de l'invention

A particular embodiment of the invention will now be described, by way of nonlimiting example, with reference to the appended schematic drawings in which:

• Figure 1 is a perspective view of a valve according to a first embodiment of the invention;
• Figure 2 is another perspective view, in section, of the valve of Figure 1;
• Figure 3 is an exploded perspective view of a valve according to a second embodiment of the invention;
• Figure 4 is an axial sectional view of the valve of Figure 3;
• Figure 5 is a perspective view, in section, of a valve according to a third embodiment of the invention;
• Figure 6 is an axial sectional view of the valve of Figure 5, mounted on a mounting bracket;
• Figure 7 is a graph illustrating the operation of the invention.
• Figure 8 is an exploded perspective view of a valve according to another embodiment of the invention;
• Figure 9 is an axial sectional view of the valve of Figure 8;
• Figure 10 is an exploded perspective view of a valve according to yet another embodiment of the invention;
• Figure 11 is an axial sectional view of the valve of Figure 10; and
• Figure 12 is an axial sectional view of a valve according to yet another embodiment of the invention

The valve of Figures 1 and 2 essentially comprises a motor 1 of a type which will be described below and, mounted on the output shaft of this motor, a shutter 2. The shutter 2 pivots in a conduit shown schematically by the broken lines 3, this duct being connected to the valve by the flange 4 in which the flap 2 is pivotally mounted.

It can be seen more particularly in FIG. 2 that the flap 2 is capable of rotating a quarter turn between a completely open, where it is parallel to conduit 3, and a fully closed position, where it is perpendicular to this conduit and resting on abutment surfaces 5 formed in the flange 4.

The abutment surfaces 5 are perpendicular to the axis of the conduit 3 and are directed one in one direction, and the other in the opposite direction, so that the edges of the flap 2 are supported on these two surfaces 5 when closed, thus forming a seal. The following will be described how the force of the shutter is supplied on the abutment surfaces.

In the embodiment of Figures 3 and 4, the gas pipe is formed of a first cylindrical conduit 10 of relatively large section, into which a second substantially cylindrical conduit 11 opens, of smaller diameter and whose axis is substantially perpendicular to the axis of the cylinder 10. The two conduits are here made in one piece. The end 12 of the conduit 11 inside the cylinder 10 supports a seat of valve 13 to form a seal with a valve head 14.

The part formed by cylinders 10 and 11 extends opposite of cylinder 11 by a housing 15 opening into cylinder 10 for receive the actuation mechanism of the valve 14. The housing 15 is itself extended by a housing 16 capable of receiving the engine actuating the aforementioned mechanism, this motor not being shown in but being of the type described below.

A bell 17 is mounted integral with the motor output shaft and is therefore locked axially. This bell 17 has holes 18 likely to receive balls 19. Consequently, the motor drives the balls 19 rotating in a plane perpendicular to the axis of this engine.

The balls 19 are also engaged in helical tracks 20 of a member 21 substantially cylindrical and locked in rotation. This blockage in rotation is obtained by balls 22 engaged in cells of a fixed guide member 23, these balls 22 cooperating with grooves 23 ' arranged parallel to the axis of the cylindrical part 21 in a surface interior 24 of this room.

The part 21 also includes an inner sleeve 25 in which is fixed the rod 26 of the valve 14 after this rod has passed through the guide piece 23.

We understand that when the balls 19 rotate in their plane driven by the bell 17, they cause an axial displacement of the part 21 since the latter is blocked in rotation. This part 21 being integral with the rod 26 of the valve 14, the rotation of the motor causes the lifting more or less important of the valve 14 of its seat 13 and therefore adjusts the flow of gas through the valve.

The tracks 20 may of course not be helical in the sense strict mathematics of the term, so that the valve lift is not necessarily proportional to the angle of rotation of the motor, but can be adjusted at will by an appropriate conformation of the tracks.

The valve of Figures 5 and 6 is also a globe valve. The valve actuation mechanism is here housed in a housing substantially cylindrical 30 and is actuated by a motor 31, the operation will be described below. The actual valve 32 is arranged to cooperate with a valve seat 33 arranged at the end a tubular conduit 34 formed in the axial extension of the housing 30.

The tubular conduit 34 is arranged to be engaged in a first bore 35 of a support piece 36. This tubular conduit 34 comprises, by elsewhere, a lateral orifice 37 disposed opposite a second bore 38 formed in the part 36 with its axis perpendicular to that of the first bore 35.

Valve 32 therefore controls the flow of fluid into bores 35 and 38.

The rod 39 of the valve 32 is guided by a guide member 40 mounted in the housing 30. This rod has its free end comprising a shoulder 41 arranged to receive one end of a helical spring 42 the other end of which bears on the bottom 43 of the housing 30.

The end of the rod 39 forms another shoulder 44 oriented towards the valve 32 opposite the shoulder 41. This shoulder 44 cooperates with cam surfaces 45 of a cam 46 mounted on the output shaft 47 of the motor 31.

It is understood that, here again, the rotation of the motor 31 against the action of compression spring 42 causes valve 32 to lift seat 33. The particular shape of the cam surfaces 45 makes it possible to determine the axial stroke of valve 32 as a function of the angle of rotation of the engine and, consequently, to regulate the passage of gas by function of this angle.

The motors 1 16, 31 used in the three embodiments which just described are of the angular solenoid type, which include a rotor and stator provided one with at least one magnet and the other with at least one control winding. The control winding is supplied with voltage slots with constant frequencies and opening duty cycle (RCO) variable. The current that results from the application of these slots of tension is appreciably constant with a few undulations. This engine is here always associated with elastic means of recall which has not been here shown only in the third embodiment in the form of the compression helical spring 42.

Figure 7 illustrates the characteristic curves of these motors, the torque being represented as a function of the angular elongation for a certain number of average intensities.

It can be seen that this motor provides constant torque over a certain angular range α ₁ , α ₂ for a given value of the intensity. More particularly, this torque is zero for a zero current and increases as a function of the intensity which traverses the control winding.

If we observe the curve with zero current, we observe that, on both sides of the range α ₁ , α ₂ the torque takes a non-zero value which tends to bring the rotor into an angular position of equilibrium α ₃ or α ₄ where, again, the torque is zero. Consequently, at zero current, the motor has an indifferent equilibrium range α ₁ , α ₂ and, on either side of this range, two equilibrium points α ₃ , α ₄ . For non-zero values of the current in the control winding, the elongations α ₃ and α ₄ are also zero torque equilibrium points. On the other hand, the angular elongation of equilibrium against the action of the return spring is between α ₁ and α ₂ , depending on the intensity.

In fact, the equilibrium points α ₃ and α ₄ correspond to the case where the poles of the magnets are interposed with those of the windings at equal distance from each other. On the other hand, the indifferent equilibrium range α ₁ , α ₂ corresponds to the case where these poles overlap at least partially.

The stator of the motor is calibrated relative to the structure of the valve so that, in the absence of current in the control winding, that is to say for an RCO equal to 1, the torque applying the flap 2 to its stops 5 or the valves 14, 32 on their seats 13, 33 either maximum or close to its maximum, as for example with a respective setting equal to α ₅ or α ₆ . Maximum sealing is thus obtained without supplying any current. It is observed that, on the other hand, it will be necessary to provide a certain minimum intensity for detaching the flap or the valve from its seat, for example a current I ₁ for an initial setting of α ₆ while not taking into account the force exerted on the origin by spring

Figures 8 to 11 show variants of the embodiment Figures 3 and 4, in which an engine of the same type as described above is used.

In the embodiment of Figures 8 and 9, the rotation stop of member 121 (homologous to member 21 of FIGS. 3 and 4) is obtained not not using balls, but using fingers 122 secured to the fixed guide 123 and passing through member 121. This crossing is effected by 124 oblong holes radially elongated to avoid hyperstatism which risk causing jamming of the organ 121. The drive in rotation is obtained by balls 219 cooperating with helical tracks 220, as before.

It will further be observed that a sealing bell 125 is mounted integral with the valve to cooperate with the guide member 123 and prevent a gas rise along the valve stem.

In the embodiment of Figures 10 and 11, all six guide balls and rotational drive of Figures 3 and 4 is replaced by three rollers 219. These rollers are engaged on the one hand in helical tracks 220 of member 221 (counterpart of member 21 of Figures 3 and 4), and secondly in grooves 222 formed in the body fixed guide 223 parallel to the axis of the valve.

The rollers 219 are crimped in a support 224 secured to the rod the valve, and the member 221 is rotated by the motor. This rotation of the member 221 consequently causes an axial displacement of the support 224, and therefore of the valve.

This arrangement has the advantage of avoiding the use of balls, relatively difficult to assemble, and can cause jamming due to components of radial forces which they induce.

In the embodiment of Figure 12, a helical ramp 301 coaxial with the motor shaft is rotated by this motor. This ramp is arranged to push a roller 302 integral with the rod 303 of the valve 304, against the action of a spring 305. The ramp could also be double acting, and therefore positively drive the valve in both meaning.

It will be noted that, in the embodiments of FIGS. 10 to 12, the valve is mounted in the opposite direction to the embodiments precedents. The casing therefore has a mounting hole, closed by a cap 306.

It will be understood that, in all of the embodiments described above, the opening and closing of the valve is produced by a motor rotary. This motor is here such that in the absence of control current, the valve is kept closed by residual magnetic forces. We could however forgo the advantages of this solution by using in all these valves of the elastic means as in the prior art.

Claims (10)

1. A gate for controlling the quantity of exhaust gas recycled in an exhaust gas recirculation system for an internal combustion engine comprising a closure member (2; 4; 32) disposed in a conduit (3; 10; 11; 35; 38) for cooperating in a substantially sealed manner, in the closed position, with a stop member (5; 13; 33) and rotary actuation means for driving the said closure member from its closed position to an open position, the said rotary actuation means including a stator and a rotor provided with at least one magnet and the other with at least one control winding, characterised by the fact that the stator and the rotor are mounted so that, in the absence of any current in the control winding, the closure member is pressed on the stop member by residual magnetic forces.
2. A control gate according to Claim 1, in which the closure member is driven directly by the said rotary actuation means.
3. A control gate according to Claim 2, in which the closure member is a flap (2) mounted in the said conduit on the axis of rotation of the rotary actuation means.
4. A control gate according to Claim 3, in which the walls of the said conduit form two shoulders (5) with opposite directions on each side of the axis of the flap, the said shoulders forming stop members and cooperating with the edges of the flap in order to form the seal.
5. A control gate according to Claim 1, in which the closure member is driven by the said rotary actuation means by means of a cam (17; 21; 45; 46).
6. A control gate according to Claim 5, in which the closure member is a valve (14; 32) arranged so as to be driven in translation by the said rotary actuation means by means of the said cam.
7. A control gate according to either one of Claims 5 and 6, in which the said cam has a first substantially cylindrical part (21; 121) fixed to the closure member and locked with respect to rotation, on which helical grooves (20; 120) are formed, arranged to cooperate with balls (19; 119) disposed in alveoli in a second part (17) fixed to the rotary actuation means and locked with respect to translation.
8. A control gate according to Claim 6, in which the said cam is formed at the end of a lever (46) mounted on the axis of rotation of the drive means and cooperates with a shoulder (44) on the valve stem.
9. A control gate according to either one of Claims 5 and 6, in which the said cam comprises a first part (221) fixed to the rotary actuation means, on which helical grooves (220) are formed, arranged to cooperate with rollers mounted on a second part locked with respect to rotation and fixed to the closure member.
10. A control gate according to either one of Claims 5 and 6, comprising a helical ramp (301) coaxial with the output shaft of the rotary actuation means and driven in rotation by the said actuation means, arranged to cooperate with a cam-follower roller (302) able to drive the closure member.

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