FR2902148A1 - METHOD AND DEVICE FOR REGULATING A RECIRCULATING GAS FLOW CIRCULATING IN A RECIRCULATION LINE OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The present invention relates to a method for controlling a flow of recirculating gas flowing in a recirculation line of an internal combustion engine, the recirculation line comprising between an upstream portion (58) and a downstream portion (59). cooling means (70) of the recirculating gas flow and short-circuiting means (80) adapted to assume two states, including an activated state in which the recirculation gas flow passes directly from the upstream portion to the downstream part, and a deactivated state in which the flow of recirculation gas passes through the cooling means. According to the invention, the method comprises the steps of detecting at least one characteristic value of the stress level of the internal combustion engine. , comparing said characteristic value with a threshold value, and activating or deactivating the short-circuiting means according to the result of the comparison.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention

  relates generally to the regulation of the flow of recirculation gas burned in a combustion chamber of an internal combustion engine and intended to be reinjected into the same combustion chamber. It relates more particularly to a method of regulating a flow of recirculating gas flowing in a recirculation line of an internal combustion engine, the recirculation line comprising, between an upstream portion and a downstream portion, means for cooling the recirculating gas flow and means of short-circuiting these cooling means adapted to take two states, including an activated state in which the flow of recirculation gas passes directly from the upstream part to the downstream part of the recirculation line without passing through the cooling means, and a deactivated state in which the flow of recirculation gas passes through the cooling means.

  The invention finds a particularly advantageous application in its application to supercharged internal combustion engines. It also relates to a device for regulating a recirculation gas flow comprising a recirculation line of an internal combustion engine comprising an upstream part intended to be connected to an exhaust line of the engine, a downstream part intended to be connected to an engine intake line, and, between said upstream portion and said downstream portion, means for cooling the recirculation gas flow and means for short-circuiting these cooling means adapted to take two states, a state of which activated in which the recirculation gas flow passes directly from the upstream portion to the downstream portion of the recirculation line without passing through the cooling means, and a deactivated state in which the recirculation gas flow passes through the cooling means . BACKGROUND OF THE INVENTION The internal combustion engines of the aforementioned type use as intake gas a mixture of fresh air and flue gas. These flue gases are commonly called recirculating gases (EGR gas). They are taken by the recirculation line in the exhaust line, directly downstream of the exhaust manifold of the internal combustion engine, and are introduced into a fresh air intake line, directly upstream of the distributor of the engine. air from the internal combustion engine. In the engines already known, there is provided on this recirculation line cooling means consisting of an air cooler and, near this air cooler, a valve that regulates the flow of burnt gases flowing in the line recirculation. This valve makes it possible to obtain an adequate mixture of fresh air and recirculation gas at the inlet of the combustion chamber in order to lower the volume of pollutant particles discharged by the engine without significantly reducing its performance.

  This valve can be arranged either at the inlet of the recirculation line, near the inlet of the air cooler, or at the outlet of the recirculation line, near the outlet of the air distributor (the cooler of the air does not occupy the same place along the exhaust line). Document US 6 971 377 for example discloses such a control device. This control device further comprises, between the inlet and the outlet of the air cooler, a bypass duct provided with a second valve allowing, when the temperature of the recirculation gas passes below a threshold value, short circuit the air cooler. This short-circuit is not controlled according to the level of stress of the engine but only as a function of the temperature of the recirculation gases in order to prevent condensation from forming in the recirculation line and at the inlet of the chamber combustion of the internal combustion engine, which would be detrimental to engine performance. In particular, the valve which regulates the flow of burnt gases flowing in the recirculation line is controlled independently of this second valve.

  However, with or without this device, we always find that when the engine is heavily loaded and the valve is closed, the engine performance is not optimal. More specifically, the applicant has highlighted, as part of its research, that the pressure of the combustion chamber inlet gas is lower when the valve is disposed at the inlet of the recirculation line at the outlet . In addition, it has also shown that the valve fouls more quickly and that the efficiency of the turbocharger of the internal combustion engine is lower when the valve is disposed at the outlet of the recirculation line rather than input.

  OBJECT OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a method and a regulating device which are adapted to increase, if necessary, the performance of the internal combustion engine whatever the location of the valve in the recirculation line. More particularly, according to the invention there is provided a control method as defined in the introduction, comprising the steps of: - detecting at least one characteristic value of the stress level of the internal combustion engine, comparing said minus a characteristic value with a threshold value; activation or deactivation of the short-circuiting means according to the result of the comparison. There is also provided a control device as defined in the introduction, in which there is provided means for detecting at least one characteristic value of the stress level of the internal combustion engine, means for storing at least one threshold value associated with said at least one characteristic value, means for comparing said at least one characteristic value with the threshold value associated with it, and means for controlling the short-circuiting means to activate or deactivate the short-circuit means; -circuitage according to the comparison result provided by the comparison means. When the valve is placed at the outlet of the recirculation line, the flow of recirculating gas begins to be cooled by the air cooler, then passes through the valve before being injected into the intake line. With such an architecture, the particles carried by the flow of recirculating gas solidify in the cooler so that they foul the valve quickly. In addition, it is understood that when the valve is thus placed, the recirculation line defines a large volume of air between its inlet and the inlet of the air cooler.

  When the valve is closed, this volume of air is a dead volume that creates disturbances on the flow of flue gas flowing in the exhaust line. These disturbances indeed modify the flow of gases in the exhaust line, and in particular disorganize the pressure waves that circulate in this line. Therefore, this dead volume disrupts the flow of flue gas flowing in the exhaust line. These disturbances generate pressure drops which induce a drop in turbine efficiency of the turbo compressor, which decreases the performance of the internal combustion engine. Conversely, when the valve is placed at the inlet of the recirculation line, it is understood that the latter defines a large volume of air between its outlet and the outlet of the air cooler. When the valve is closed, this volume of air forms a dead volume which creates disturbances on the flow of fresh gas circulating in the intake line. These disturbances indeed modify the flow of gases in the intake line, and in particular disorganize the pressure waves which, if they were properly organized, would favor the pressurization of the fresh air at the inlet of the combustion chamber. of the motor. This dead volume therefore limits the use of this phenomenon of pressure waves to increase the fresh air filling of the combustion chamber; it accordingly reduces the performance of the internal combustion engine.

  Thus, thanks to the invention, when the internal combustion engine is strongly stressed, the valve is closed so that it blocks the circulation of the gases in the recirculation line and the short-circuiting means are activated in such a way as to reduce the importance of the dead volume, the air included in the air cooler no longer participating in this dead volume. The disturbances caused by the dead volume then decrease in intensity which allows the pressure waves flowing in the intake line or in the exhaust line (depending on the location of the valve) to be undisturbed so that the engine performance is little changed by the presence of this recirculation line. Other advantageous and non-limiting features of the regulation method according to the invention are as follows: the short-circuiting means are activated when the detected characteristic value characterizes a level of solicitation of the motor greater than that corresponding to the threshold value, and disabling the shorting means when the detected characteristic value characterizes a motor bias level lower than that corresponding to the threshold value; the recirculation line comprising a valve, the valve is closed when the detected characteristic value characterizes a motor biasing level higher than that corresponding to the threshold value, and the valve is opened when the detected characteristic value characterizes a solicitation level; motor lower than that corresponding to the threshold value; said at least one characteristic value comprises the required torque and / or the speed of the internal combustion engine; and both the required torque and the speed of the internal combustion engine are detected, the required torque is compared with the threshold value associated with it and the speed of the internal combustion engine with the associated threshold value, and the shorting means are activated or deactivated according to the result of the two comparisons.

  Other advantageous and non-limiting features of the regulating device according to the invention are the following: the cooling means comprise an inlet and an outlet each opening respectively in the upstream and downstream parts of the recirculation line, and the short-circuit means circuit comprise a movable flap between two stable positions, a position corresponding to the activated state of the short-circuiting means in which the shutter closes the inlet and the outlet of the cooling means and connects the upstream and downstream parts of the recirculation line, and a position corresponding to the deactivated state of the short-circuiting means in which the flap separates the upstream and downstream parts of the recirculation line and opens the inlet and outlet of the cooling means; the flap is pivotally mounted and is controlled by the control means between two stable angular positions; the recirculation line comprises a valve disposed at the inlet of the upstream portion of the recirculation pipe, near the inlet of the cooling means; the recirculation line comprises a valve disposed at the outlet of the downstream part of the recirculation pipe, near the outlet of the cooling means; and the detection, storage and comparison means are integrated in an electronic and / or computer control device of the internal combustion engine.

  DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

  The following description with reference to the accompanying drawings given as non-limiting examples, will make it clear what the invention is and how it can be achieved.

In the accompanying drawings:

  - Figure 1 is a schematic overview of a first embodiment of an internal combustion engine comprising a control device according to the invention;

  FIGS. 2A and 2B are diagrams of operation of the control device of FIG. 1; and

  FIG. 3 is a schematic overview of a second embodiment of the internal combustion engine of FIG.

  As a preliminary, it will be noted that, from one figure to another, the identical or similar elements of the different embodiments of the invention will, as far as possible, be referenced by the same reference signs and will not be described. Everytime.

  In the description, the terms upstream and downstream will be used in the direction of the flow of air, from the point of taking the fresh air into the atmosphere to its outlet by an expansion pot 40.

  Figures 1 and 3 schematically shows an internal combustion engine 10 which comprises a combustion chamber 11, here four cylinders 11A.

  At the outlet of the combustion chamber 11, the internal combustion engine 10 comprises an exhaust manifold 13 which opens into a burnt gas exhaust line 20 extending as far as the expansion vessel 40.

  In addition, the internal combustion engine 10 comprises on this exhaust line 20 a turbine 31 of a turbocharger 30 rotating a compressor 32. Upstream of the combustion chamber 11, the internal combustion engine 10 has a line intake 23 which comprises successively an air filter 60 which filters the fresh air taken from the atmosphere, the compressor 32 which compresses the fresh air filtered by the air filter 60, and finally a main air cooler 43 which cools the fresh air compressed by the compressor 32. This fresh air then opens into an air distributor 12 which brings the fresh air into each of the cylinders 11A of the combustion chamber 11. The internal combustion engine 10 comprises by elsewhere a recirculation line 50 which is stitched on the exhaust line 20, between the exhaust manifold 13 and the turbine 31, and which opens into the intake line 23, between the main air cooler 43 and the repai 12. This recirculation line 50 makes it possible to inject into the intake line 23 a portion of the combustion flue gases, called recirculation gases, to produce an intake mixture comprising fresh air. and flue gases. It therefore reduces the volume of polluting particles emitted by the engine. The recirculation line 50 comprises an upstream portion 58 connected to the exhaust line 20, a downstream portion 59 connected to the inlet line 23, and, between the upstream portion 58 and the downstream portion 59, a valve 51 juxtaposed, on the one hand, to cooling means 70 of the recirculation gas flow, and, on the other hand, to short-circuiting means 80 of these cooling means 70. According to a first embodiment of the invention represented in FIG. 1, the recirculation line 50 comprises an upstream portion 58 of very short length which opens into the valve 51 and a downstream portion 59 of longer length making it possible to connect the cooling means 70 and the shortcircuiting means 80 to the line 23. More specifically, as shown in FIGS. 2A and 2B, the valve 51 has an inlet which is connected to the upstream portion 58 of the recirculation line 50 and in which is disposed a valve seat 55, and a Release plugging in a volume 57 which is delimited by a housing fixed to the valve 51 and which is connected to the downstream portion 59 of the recirculation line 50. The valve 51 comprises a valve 52 provided with a cylindrical body 54 and a head 53 adapted to cooperate with the valve seat 55. It is intended to regulate the flow rate of the recirculating gas flow flowing in the recirculation line 50. The valve 52 is here controlled in position by an electromagnetic coil 56 fixed in the frame of the valve 51 around the cylindrical body 54 of the valve 52. Therefore, when an electric current passes through the electromagnetic coil 56, this coil exerts an electromagnetic force on the valve 52 which plates the latter on its seat and obstructs the line of On the other hand, when no electric current passes through the electromagnetic coil 56, the pressure forces exerted on the valve 52 raise it it sits, thus allowing the recirculation gases to pass through the recirculation line 50.

  The cooling means comprise a water cooler 70 with water internally comprising a cooling channel whose inlet 71 and outlet 72 open into the volume 57, close to each other. The inlet 71 is more precisely located on the side of the upstream portion 58 of the recirculation line 50 and the outlet 72 on the side of the downstream portion 59 of the recirculation line 50. The short-circuiting means here consist of a flap 80 mounted on a shaft 81 integral in rotation with an electric motor (not shown) and pivotable between two stable angular positions. These two angular positions correspond to two distinct states of the shorting means, an activated state and a deactivated state. The shutter 80 has a rectangular shape. Its two lateral edges can slide against the walls of the casing defining the volume 57. Its two end edges can in turn each be supported, depending on the angular position of the flap 80, on one or the other of two distinct zones. of the casing defining the volume 57. Thus, as shown in FIG. 2B, when the short-circuiting means 80 are in the activated state, the end edges of the flap 80 bear on first zones of the casing so as to hermetically separate the volume 57 in two sub-volumes. A first sub-volume into which the inlet 71 and outlet 72 of the air cooler 70, and a second sub-volume into which the outlet of the valve 51 and the inlet of the downstream portion 59 of the recirculation line 50. Therefore, in the activated state, the short-circuiting means close off the inlet 71 and the outlet 72 of the cooling means 70 and connect the upstream 58 and downstream 59 parts of the recirculation line 50. On the other hand, as the 2A, when the short-circuiting means 80 are in the deactivated state, the end edges of the flap 80 are supported on other areas of the housing so as to hermetically separate the volume 57 into two other sub-volumes. A first sub-volume into which the inlet 71 of the air cooler 70 and the outlet of the valve 51 open, and a second sub-volume into which the outlet 72 of the air cooler 70 and the inlet of the downstream part 59 of the recirculation line 50. Consequently, in the deactivated state, the short-circuiting means separate the upstream 58 and downstream 59 parts of the recirculation line 50 and open the inlet 71 and outlet 72 of the cooling means 70 The flow of recirculating gas circulating in the recirculation line 50 is thus first cooled in the air cooler 70 before being injected into the intake line 23. The electromagnetic coil 56 of the valve 51 and the electric motor actuating the flap 80 are both powered by a battery and controlled by control means integrated with an electronic device and / or computer control of the internal combustion engine. This electronic and / or computer device also comprises means for detecting characteristic values of the stress level of the internal combustion engine 10, namely here means for detecting the engine speed and means for detecting the required torque. To do this, the required torque detection means can for example detect the position of an accelerator pedal connected to the engine. The electronic and / or computer device further comprises means for storing a threshold value associated with the required torque and a threshold value associated with the engine speed. These threshold values are fixed and are determined during the development phases of the engine. The electronic and / or computer device finally comprises means for comparing the detected required torque with the threshold value associated with it and the detected engine speed with the threshold value associated therewith. For the implementation of the invention, the method for regulating the recirculation gas flow comprises three successive steps. During a first detection step, the electronic and / or computer device detects the required torque and the speed of the internal combustion engine 10. During a second so-called comparison step, it compares each of these detected values with the threshold value associated with it and which is stored in the memory means.

  At the end of this second step, it controls with the aid of its control means the activation or deactivation of the short-circuiting means 80 as a function of the result of the comparison provided by the comparison means. More specifically, it activates the short-circuiting means 80 if the required torque and the engine speed are both greater than their threshold value, which characterizes a high level of stress on the internal combustion engine 10. In this case, the electronic and / or computer device then further controls the closing of the valve 52 of the valve 51. Otherwise, if at least one or other of these characteristic values is lower than its threshold value, the electronic device and / or The computer deactivates the short-circuiting means 80 and opens the valve 52. Thus, when the internal combustion engine is under heavy load, the recirculation line 50 is completely obstructed so that the engine burns only fresh air. in its combustion chamber 11. It is therefore adapted to deliver a large torque. In addition, thanks to the invention, the dead volume in which stagnant recirculation gas has a relatively small length insofar as the air cooler 70 is short-circuited. The flow of fresh air passing through the intake line 23 is therefore little disturbed by the presence of this dead volume, so that the engine performance is optimal. As a variant, the electronic and / or computer device could be adapted to activate or deactivate the short-circuiting means 80 only as a function of one or other of the characteristic values that are the required torque and the engine speed. 10. Any other characteristic value of the engine load level may also be suitable. According to a second embodiment of the invention shown in FIG. 3, the recirculation line 50 comprises an upstream portion 58 of considerable length and a downstream portion 59 of short length. In this embodiment, the valve 51 is disposed downstream of the cooling means 70 and short-circuiting 80 so that the volume 57 is connected, on one side, to the outlet of the upstream portion 58 of the recirculation 50, and the other at the inlet of the valve 51. The implementation of the invention remains however identical.

  Thus, when the internal combustion engine 10 is highly stressed, the short-circuiting means 80 are activated. Consequently, the flow of burnt gases passing through the exhaust line 20 is little disturbed by the dead volume constituted by the air included in the upstream portion 58 of the recirculation line 50, so that the turbine 31 of the turbo compressor is rotated at an optimum speed. The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.

Claims (11)

  A method of regulating a flow of recirculating gas flowing in a recirculation line (50) of an internal combustion engine (10), the recirculation line (50) comprising, between an upstream portion (58) and a downstream portion (59), cooling means (70) of the recirculating gas flow and short-circuiting means (80) of said cooling means (70) adapted to assume two states, including an activated state in which the recirculating gas flow passes directly from the upstream portion (58) to the downstream portion (59) of the recirculation line without passing through the cooling means (70), and a deactivated state in which the recirculation gas flow passes through the cooling means (70), characterized in that the method comprises the steps of: detecting at least one characteristic value of the stress level of the internal combustion engine (10), - comparing said at least one characteristic value with a v threshold threshold, - activation or deactivation of the short-circuiting means (80) according to the result of the comparison.   2. Control method according to the preceding claim, characterized in that activates the short-circuiting means (80) when the characteristic value detected characterizes a stress level of the internal combustion engine (10) greater than that corresponding to the threshold value, and disabling the short-circuiting means (80) when the detected characteristic value characterizes a stress level of the internal combustion engine (10) lower than that corresponding to the threshold value. 25   3. Control method according to the preceding claim, characterized in that, the recirculation line (50) comprising a valve (51), the valve (51) is closed when the characteristic value detected characterizes a level of stress of the combustion engine internal (10) greater than that corresponding to the threshold value, and the valve (51) is opened when the detected characteristic value 30 characterizes a stress level of the internal combustion engine (10) lower than that corresponding to the threshold value.   4. Control method according to one of the preceding claims, characterized in that said at least one characteristic value comprises the required torque and / or the speed of the internal combustion engine (10).   5. Control method according to the preceding claim, characterized in that it detects both the required torque and the speed of the internal combustion engine (10), the required torque is compared with the threshold value associated with it and the RPM of the internal combustion engine (10) with the associated threshold value, and the short-circuiting means (80) is activated or deactivated according to the result of the two comparisons.   A device for regulating a recirculating gas flow having a recirculation line (50) of an internal combustion engine (10) comprising an upstream portion (58) for connection to an exhaust line (20). ) of the internal combustion engine (10), a downstream part (59) intended to be connected to an intake line (23) of the internal combustion engine (10), and, between said upstream part (58) and said part downstream (59) cooling means (70) of the recirculating gas flow and short-circuiting means (80) of said cooling means (70) adapted to take two states, including an activated state in which the flow of recirculating gas passes directly from the upstream portion (58) to the downstream portion (59) of the recirculation line (50) without passing through the cooling means (70), and a deactivated state in which the flow of gas from recirculation passes through the cooling means (70), characterized in that means for detecting at least one characteristic value of the biasing level of the internal combustion engine (10), means for storing at least one threshold value associated with said at least one characteristic value, means for comparing the said at least one characteristic value with the threshold value associated therewith, and control means of the short-circuiting means (80) for enabling or disabling the short-circuiting means (80) according to the comparison result provided by the means of comparison.   7. Control device according to the preceding claim, characterized in that the cooling means (70) comprise an inlet (71) and an outlet (72) opening respectively in the upstream (58) and downstream (59) portions of the line of recirculation (50) and in that the short-circuiting means comprise a flap (80) movable between two stable positions, a position corresponding to the activated state of the short-circuiting means in which the flap (80) closes the inlet (71) and the outlet (72) of the cooling means (70) and connects the upstream (58) and downstream (59) portions of the recirculation line (50), and a position corresponding to the deactivated state of the means short-circuiting circuit in which the flap (80) separates the upstream (58) and downstream (59) portions of the recirculation line (50) and opens the inlet (71) and outlet (72) of the cooling means (70) .   8. Control device according to the preceding claim, characterized in that the flap (80) is pivotally mounted and is controlled by the control means between two stable angular positions.   9. Control device according to one of the two preceding claims, characterized in that the recirculation line (50) comprises a valve (51) disposed at the inlet of the upstream portion (58) of the recirculation pipe (50), near the inlet (71) cooling means (70).   10. Control device according to one of claims 7 and 8, characterized in that the recirculation line (50) comprises a valve (51) disposed at the outlet of the downstream portion (59) of the recirculation pipe (50). near the outlet (72) of the cooling means (70).   11. Control device according to one of claims 6 to 10, characterized in that the detection, storage and comparison means are integrated in an electronic device and / or computer control of the internal combustion engine (10). 25