EP2240679B1 - Motor vehicle internal combustion engine egr loop - Google Patents

Description

The invention relates, with reference to the figure 7 in the appendix, the EGR loop of an internal combustion engine of a motor vehicle, comprising the engine 21, an exhaust manifold 22 for the combustion gases, a turbine 25 of a turbo-compressor 24, the recirculation loop of the gases 28 (exhaust) (EGR), with a cooler 29 and the low-pressure three-way valve disposed upstream of the compressor 26 of the turbo-compressor 24 and connected to it by its output and having two inputs for receiving fresh air and the cooled exhaust gas, a mixture whose pressure is increased in the compressor 26, and an intake manifold 23 of the engine for receiving the exhaust gas and the compressor air.

The EGR loop aims to reduce the emission of nitrogen dioxide, by reducing the combustion temperature, by slowing down the combustion of the combustion mixture and absorbing part of the calories. The cooler of the EGR loop makes it possible to lower the combustion temperature at high speed (high load).

• Ainsi, l'invention concerne un mode d'utilisation particulier de la boucle EGR ci-dessus, caractérisé par le fait que
• le débit de l'air frais dans la voie d'arrivée de l'air de la vanne EGR étant maximum,
• on ouvre progressivement la voie des gaz EGR dans la vanne et,
• avant que le débit des gaz EGR dans la vanne n'augmente plus,
• on ferme progressivement la voie d'arrivée de l'air frais pour continuer de faire croître le débit des gaz EGR, suivant une courbe monotone croissante.

L'invention est mise en oeuvre avec une vanne trois voies à deux volets pour les deux voies air frais et gaz EGR, respectivement. Le déphasage de la fermeture de la voie d'arrivée d'air frais, peut également être réalisé avec une vanne trois voies monovolet, impliquant des zones angulaires beaucoup plus étroites.Several operating modes of the three-way valve and thus the engine can be envisaged. Two devices for regulating the flow of EGR gas are presented in the US 2005/02 41702 A1 and the FR 2 806 448 A1 . The engine may only receive fresh air with no recirculated exhaust. The engine can receive fresh air mixed with a portion of the exhaust gas, the pressure difference between the exhaust and the inlet of the compressor of the turbo-compressor being sufficient to ensure the recirculation of the exhaust gas. When the pressure difference is not sufficient for the recirculation of the exhaust gas and to ensure the correct EGR rate, it is possible to create a throttling backpressure downstream of the EGR loop, so that force a portion of the exhaust gas to the engine intake lane. This solution, by its complexity, is however not very satisfactory and the invention of the present application is another solution to the problem of creating a back pressure to ensure a correct flow EGR.

• Thus, the invention relates to a particular mode of use of the EGR loop above, characterized by the fact that
• the flow rate of the fresh air in the air inlet channel of the EGR valve being maximum,
• the EGR gas channel is gradually opened in the valve and,
• before the flow of EGR gas in the valve increases,
• the fresh air inlet is gradually closed to continue to increase the flow of the EGR gas, following a monotonous curve increasing.

The invention is implemented with a two-way three-way valve for the two fresh air and EGR gas channels, respectively. The phase shift of the closure of the fresh air intake channel can also be achieved with a three-way valve monovolt, involving angular areas much narrower.

In the embodiment according to the invention, with a three-way valve with two flaps, the flow of EGR gas in the inlet channel EGR of the valve starting to decline after a rotation of the corresponding flap of about 55 ° it is in this angular position of the EGR gas shutter that the intake flap of the fresh air is started to close the fresh air intake path in the EGR valve. The rotation of the intake flap (5) can be carried out until it is rotated 90 °. This rotation can lead to completely close the air inlet (2). Alternatively, the pipe is closed only partially, for example by a flap whose diameter is smaller than the diameter of the pipe.

Note that in the document engine US 2005/0193978 , the overpressure defined by a given valve is always at the level corresponding to the operation of the engine; if the overpressure varies by this valve, the amount of air admitted varies too.

• les figures 1a, 1b, 1c, 1d illustrent les quatre modes d'utilisation de la vanne trois voies de la boucle EGR dont l'utilisation particulière est revendiquée par la présente demande ;
• les figures 2a, 2b, 2c représentent les courbes de débit d'air (1a), de débit naturel de gaz d'échappement EGR (dgn) et de débit, forcé selon l'invention, de gaz d'échappement EGR (dgf), en fonction des positions angulaires (α) des volets correspondants ;
• la figure 3 est une vue en perspective de la cinématique de la vanne trois voies à deux volets, volet d'air ouvert et volet des gaz fermé ;
• la figure 4 est une vue de la vanne de la figure 3, volet des gaz en position d'ouverture partielle ;
• la figure 5 est une vue de la vanne de la figure 3, volet des gaz ouvert et volet d'air fermé ;
• la figure 6 est une vue partielle en perspective de la cinématique d'une vanne trois voies selon une variante du mécanisme de déphasage temporel de la fermeture du volet d'air par rapport à l'ouverture du volet des gaz et
• la figure 7 représente de façon simplifiée, la boucle EGR utilisée selon l'invention.

The invention will be better understood with the aid of the following description of the mode of use of the three-way valve and therefore of the EGR loop, as well as the three-way valve itself, with reference to the drawing in the appendix, on which

• the Figures 1a, 1b, 1c, 1d illustrate the four modes of use of the three-way valve of the EGR loop whose particular use is claimed by this application;
• the Figures 2a, 2b, 2c represent the curves of air flow (1a), natural flow rate of exhaust gas EGR (dgn) and flow rate, forced according to the invention, of exhaust gas EGR (dgf), as a function of the angular positions ( α) corresponding components;
• the figure 3 is a perspective view of the kinematics of the three-way two-part valve with open air flap and closed flap;
• the figure 4 is a view of the valve of the figure 3 , flap of gases in partial open position;
• the figure 5 is a view of the valve of the figure 3 , open gas shutter and closed air shutter;
• the figure 6 is a partial perspective view of the kinematics of a three-way valve according to a variant of the temporal phase-shift mechanism of the closure of the air shutter with respect to the opening of the flap of the gases and
• the figure 7 represents in a simplified way, the EGR loop used according to the invention.

The EGR valve 1 of Figures 1a, 1b, 1c , schematically, comprises an air inlet 2, a recirculated exhaust gas inlet 3 and an air and gas outlet 4.

The valve 1 is here a two-part valve, a flap 5 in the air inlet duct 2 and a flap 6 in the gas inlet duct 3.

Firstly, the air flap 5 is in an angular position (0 °) allowing a maximum air flow in the track 2 and the arrival flap of the gases 6, in an angular position (90 °) shutting off way 3.

Then, without the air flap 5 is rotated, the gas inlet flap 6 - begins to pivot to gradually open the track 3 EGR exhaust ( figure 1a ). This is the zone I of the curves 2. Then, the air flap 5 remaining in the same position of maximum opening of the air inlet 3, the flap of the gas 6 pivots to considerably open the way of gas 6 ( figure 1b ). This is the zone II of the curves 2. In a certain angular position of the flap of the gases 6, here 35 °, that is to say after a rotation of 55 °, the flow of the gases in the way 3 does not increase substantially and, while continuing to rotate the flap of the gas 6, then starts to rotate the air flap 5 to close the air inlet duct 2, with a corresponding phase shift, and thus, force the engine to draw more EGR gas ( figure 1c ).

Enter Zone III curves 2, the exhaust flow curve bending to continue to rise.

This zone III extends until the gas flap 6 reaches the angular position O ° of maximum opening of the gas inlet channel 3 and the air flap is in the angular position (90 °) total or partial closure of the air inlet 2.

For the implementation of the supply of the three-way EGR valve 1, as defined above, this three-way valve has the kinematics which will now be described with reference to the Figures 3 to 5 .

The kinematics of the three-way valve 1 comprises a gear extending, here, between a DC motor 7 and two shafts 51, 61 for rotating the air flap 5 and the gas flap 6, respectively. The two shafts 51, 61 extend parallel to each other.

The shaft 14 of the motor 7 is secured to a pinion 8 for driving an intermediate toothed wheel 9 bearing a peripheral toothing 10 and a central toothing 11.

The peripheral toothing 10 of the intermediate wheel meshes with a ring gear 12 for rotating the air flap 5. The ring gear 12 is free to rotate relative to the axis 51 of the flap 5. The rotational drive this flap 5 by the ring 12 is via a drive finger 15 which is itself integral in rotation with the axis 51 of the flap 5. This finger 15 is disposed at rest against an adjustable stop 16 integral with the body of the valve (not shown). The ring 12 has an angular notch 17 adapted to allow the free rotation of the ring 12 on a defined angular sector, without driving the finger 15, that is to say the flap 5. It is when the ring 12 is driven in rotation beyond this angular sector, in one direction or the other, that the edge of the notch 17 then drives the finger 15.

The central toothing 11 of the intermediate wheel 9 meshes with a ring gear 13 for rotating the flap of the gas 6. The ring gear 13 is rotationally integral with the axis 61 of the flap 6.

The flap 6 is therefore rotated directly by the rotation of the ring 13, while the flap 5 is rotated only when the ring 12 rotates the finger 15.

In the example, the motor 7, by its pinion 8, rotated in the counterclockwise direction, drives the intermediate wheel 9 in rotation in the direction of clockwise. In turn, the wheel 9, by its teeth 10, 11 drives, in the opposite direction of the needles, the two toothed rings 12, 13, which are thus rotated by the same intermediate wheel 9, but via two gear teeth 10, 11. The gear ratio between the shaft 14 of the motor 7 and the flap of the gas 6 is here 15.67, the ratio between the shaft 14 and the air flap 5 when is driven being 6.67.

The phase shift mechanism of the closure of the air shutter 5 will now be described.

The Figures 3, 4 , and 5 show the crowns and toothed wheels at different stages of rotation of the pinion 8.

Of the figure 3 to the figure 4 , the rings 12 and 13 are driven in the opposite direction of the clockwise so causing the opening of the flap 6 while the flap 5 remains stationary and thanks to the angular notch 17. On the position of the figure 4 , one of the edges of this notch 17 comes into contact with the finger 15.

The rotation of the ring 12 then continues towards the position shown figure 5 , the finger 15 (and therefore the flap 5) then being rotated. The shutter 5 thus closes with a temporal phase shift allowed by the notch 17.

An alternative embodiment of the phase shift mechanism is shown in FIG. figure 6 . According to this variant, a cross member 50 with two radial arms 52, 53 is mounted on the shaft 51 of the flap 5. Each of the arms 52, 53 comprises at its end a driving pin 54, 55, extending substantially parallel to the tree 51.

In the ring gear 12 are formed two circular lights 56, 57 for driving fingers 54, 55 in circular translation. The fingers 54, 55 extend respectively in these two lights 56, 57.

As long as the fingers 54, 55 are not resting against one of the bottoms 58 of the slots 56, 57, the shaft 51 and the air shutter 5 can not be rotated. As soon as the fingers 54, 55 abut against the respective bottoms of the two lights 56, 57, the ring gear 12 drives them with it, causing the flap 5 to rotate.

To ensure the correct operation of the three-way valve, the angular opening of the lights must be less than 180 °. If α _g is the angle of rotation of the gas flap 6, α _a , the angle of rotation of the air flap 5, the relation (1) must be satisfied. $$\left({\mathrm{\alpha }}_{\mathrm{boy\; Wut}}-{\mathrm{\alpha }}_{\mathrm{at}}\right)\times \frac{{\mathrm{\alpha }}_{\mathrm{boy\; Wut}}}{{\mathrm{\alpha }}_{\mathrm{at}}}<180$$

If we consider α _g = 90 ° ( figure 2b ), then the angle of rotation α _a of the air flap 5 must satisfy the relation (2) $${\mathrm{\alpha }}_{\mathrm{at}}>30°$$

doit alors satisfaire la relation (3) $$\mathrm{R}<3$$

The gear ratio $\mathrm{R}=\frac{\alpha \mathrm{boy\; Wut}}{\alpha \mathrm{at}}$

must then satisfy the relationship (3) $$\mathrm{R}<3$$

In the example mentioned above, we considered $$\mathrm{R}=\frac{15.67}{6.67}=2.35$$

The circular lights 56, 57 are formed in the ring 12 relative to the toothed sector of the ring 12 taking into account the amplitude of the angular rotation of the gas flap 6 before the air flap 5 begins to rotate.

The valve that has just been described is remarkable for its uniqueness of control, at the single level of the DC motor 7, which makes it a better price and a smaller footprint.

This control can be achieved using an H bridge, well known to those skilled in the art, with two pairs of switches in series and the component to be controlled - here the motor - connected to the two middle points of two pairs of switches, the two pairs being connected between a battery voltage and ground.

Claims (4)

1. Mode of use of a motor vehicle internal combustion engine EGR loop, comprising the engine (21), a combustion gas exhaust manifold (22), a turbocharger (24), a turbine (25), the exhaust gas recirculation (EGR) loop (28) with a cooler (29) and a low-pressure three-way valve (30) positioned upstream of the turbocharger compressor (26) and connected thereto by its outlet and comprising two inlets for receiving fresh air and the cooled exhaust gases in a mixture the pressure of which is increased in the compressor, the three-way valve (1) having two flaps (5, 6) for the two paths, fresh air (2) and EGR gas (3) respectively,
   and an engine intake manifold (23) for receiving the exhaust gases and the air from the compressor (26),
   characterized in that:

   - with the fresh air flow rate in the air inlet path (2) of the EGR valve (1) set at a maximum,

   - the path (3) for the EGR gases in the valve is progressively opened, and

   - before the EGR gas flow rate in the valve increases any further,

   - the fresh air inlet path (2) is progressively closed in order to continue to cause the EGR gas flow rate to increase on an increasing monotonous curve,

   the EGR gas flow rate in the EGR inlet path (3) of the valve (1) beginning to drop after a rotation of the corresponding flap (6) through about 55°, it is from this angular position of the EGR gas flap (6) that the fresh air intake flap (5) begins to be turned in order to close the fresh air inlet path (2) in the EGR valve.
2. Mode of use according to Claim 1, characterized in that the intake flap (5) is rotated until it has been turned through 90°.
3. Mode of use according to one of Claims 1 and 2, characterized in that the intake flap (5) is rotated until the air inlet path (2) is completely shut off.
4. Mode of use according to one of Claims 1 and 2, characterized in that the intake flap (5) is rotated until the air inlet path (2) is partially shut off.

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