WO2007093729A2

WO2007093729A2 - Air intake circuit for internal combustion engine

Info

Publication number: WO2007093729A2
Application number: PCT/FR2007/050777
Authority: WO
Inventors: Benoît FROUVELLE
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2006-02-14
Filing date: 2007-02-12
Publication date: 2007-08-23
Also published as: EP1984609A2; FR2897393B1; WO2007093729A3; FR2897393A1

Abstract

The invention concerns an air intake circuit (1) for internal combustion engine (2). Said circuit (1) comprises a main air pipe (8) connecting a turbocharger (3) and an engine intake manifold (2.1). A cooler (9) mounted in series with the main air pipe (8) cools the air from the turbocharger (3). A bypass pipe (10) comprises one first end (11) connected to the main pipe (8) upstream of the cooler at an upstream junction point (12) upstream, and a second end (13) connected to the main pipe (8) downstream of the cooler at a downstream junction point (14). To control proportionally the total gas flow circulated to the intake manifold, a proportional valve (21) is positioned downstream of the downstream junction (14).

Description

INTAKE AIR CIRCUIT FOR INTERNAL COMBUSTION ENGINE

The present invention provides an intake air circuit for an internal combustion engine. The invention particularly aims to simplify the structure of such a circuit, while facilitating the control of the flow rate and temperature of the air inside this circuit. The invention finds a particularly advantageous application with motor vehicle diesel engines, including passenger car engines.

Diesel engines are internal combustion engines that can consume heavy fuels, such as diesel or fuel oil. In these engines, combustion is triggered by self-ignition of the air in highly compressed fuel. For this purpose, the fuel is injected into a combustion chamber, while the air is fed into this chamber through an intake manifold of the engine.

To improve their performance, diesel engines generally include a turbocharger. This turbocharger, driven by the engine exhaust gas, produces pressurized air called charge air. This supercharging air increases the air flow to the intake manifold. However, the compression of the air by the turbocharger causes a rise in the temperature of the air at the intake. This increase in temperature results in the degradation of the thermodynamic efficiency of the engine, as well as the increase of emissions of particles harmful to the environment.

This is the reason why the turbocharged diesel engines almost always include a charge air cooler (RAS abbreviated) positioned at the outlet of the turbocharger. This cooler cools the charge air by heat exchange with a flow of outside air or a coolant.

Cooling of the air through the cooler reduces the temperature of the engine exhaust. However, during the first minutes of operation of the engine, the temperature of the exhaust gas is unfavorable to the initiation of an oxidation catalyst connected to the output of the engine and treating particles harmful to the environment. During the first minutes of operation, it may therefore be necessary not to cool the air of the intake circuit.

In addition, the engine generally includes a gas recirculation circuit (EGR) which injects the exhaust gases into the intake manifold to burn them again. To control the composition between the exhaust gas and the air entering the engine, the air flow is indirectly controlled via a valve in the recirculation circuit. However, under certain operating conditions of the engine, it may be necessary to greatly reduce the air flow, while a small pressure difference reigns across the recirculation circuit. Under these operating conditions, the air flow rate is limited directly inside the intake circuit. In addition, diesel engines usually include a particle filter connected to the output of the oxidation catalyst which further limits the emission of particles harmful to the environment. To regenerate the particulate filter, the temperature of the flue gases is raised to reach the soot combustion temperature of the particulate filter. This regeneration phase can be achieved by greatly reducing the amount of air in the intake circuit. In addition, under certain operating conditions where an unfavorable external temperature or urban running, the supercharged air is not cooled in order to increase the temperature of the engine exhaust gases.

Finally, for reasons of approval, it is not enough to be content with injection techniques to stop the engine. Indeed, these techniques can cause jolts, vibrations, or unwanted noise. In addition to these techniques, the air flow at the intake is greatly reduced in order to stop the engine more adequately. In summary, there are engine operating conditions in which it may be necessary to proportionally control the air flow entering the intake, and / or control the cooling of the air, allowing the air to go through the cooler or to avoid it. A so-called "double doser" device is known that makes it possible to meet these needs. This device takes the form of a Y-shaped housing connecting a chiller outlet and an outlet of a bypass duct bypassing the chiller. This device comprises a first valve mounted on the bypass duct and a second valve mounted on the duct of the cooler.

As described in US-6868840, the two valves may be proportional valves. It is thus possible to control the flow of air entering the engine, as well as the distribution of gases passing through the cooler. and the bypass duct. Such a system satisfies satisfactorily the needs of flow control and management of air cooling. However, the cost of two proportional valves is relatively high and the implementation of these two valves can be binding in terms of packaging.

In a known dual metering device, the first valve (mounted on the bypass duct) is of the all-or-nothing type, while the second valve (mounted on the duct of the cooler) is of the proportional type. When the first valve is closed, all the air passes through the cooler. The air is thus cooled and the second valve makes it possible to control the flow proportionally. When the first valve is open and the second valve closed, all air passes through the bypass duct. The partial or total opening of the second valve controls the level of air cooling, but does not control the total flow of air entering the engine.

In another known dual composite metering device, the first valve (mounted on the bypass duct) is of the proportional type and the second valve (mounted on the cooler duct) is of the all-or-nothing type. When the second valve is closed, all the air passes through the bypass duct and the first valve allows proportional control of the air flow. When the second valve is open, the air is cooled by closing the first valve. In this case, all the air passes into the cooler. On the other hand, it is impossible to control the airflow while maintaining optimal cooling. Indeed, a partial or total opening of the first valve causes degraded cooling of the air but does not control the total flow of air sent to the inlet.

The dual dual doser is less expensive than the dual proportional doser, but is only partially satisfactory. Indeed, the control of the air flow is possible only in mode minimum cooling (all air passes through the chiller) or maximum cooling mode (all air passes through the bypass circuit).

The purpose of the invention is to simplify the structure and cost of existing intake air circuits, while allowing precise control of the flow rate and temperature of the air supplied to the engine intake.

For this purpose, in the invention, the completion of the functions of proportional control of the air flow and control of the cooling is separated by means of an architecture composed of two devices adapted to each of these two functions.

The air circuit according to the invention thus comprises a "shutter" type selection valve mounted on a branch between the cooler and the bypass duct. This selection valve makes it possible to pass air either into the cooler or into the cooling circuit. This selection valve thus makes it possible to control the cooling of the circuit air. The air circuit according to the invention further comprises a proportional type valve positioned downstream of the cooler and the junction between this cooler and the bypass duct. This valve provides proportional control of the total air flow to the inlet, ie air from the chiller and bypass duct, and, where applicable, gas from the exhaust system. recirculation.

In a first embodiment, the selection valve is mounted on the branch between the cooler and the bypass duct, downstream of the cooler and the bypass duct.

In a second embodiment, the selection valve is mounted on the branch between the cooler and the bypass duct upstream of the cooler and the bypass duct. This realization can be interesting in the cases where the access of the downstream junction between the cooler and the bypass duct is difficult. In addition, this embodiment makes it easy to complete a circuit comprising, after manufacture, a proportional valve positioned downstream of the cooler.

These embodiments meet the functional needs of flow control and air temperature, as well as a dual proportional proportioner, while being simpler since only one of the two actuators is proportional. This results in a simplified control and a reduced cost, a priori of the same order as the price difference between a dual proportional proportioner and double mixed metering.

Moreover, compared to a dual dual doser, the control possibilities offered by the invention are more numerous, the dual dual doser not allowing to control the flow in all cases of engine operation.

In addition, the invention offers an additional degree of freedom in terms of implementation on the engine. The invention therefore relates to an intake air circuit for an internal combustion engine, this circuit comprising:

a main air duct interconnecting a turbocharger and an intake manifold of the engine, this turbocharger delivering pressurized air to the intake manifold via this main air duct,

a cooler connected in series with the main air duct for cooling the air coming from the turbocharger, and

a bypass pipe comprising a first end connected to the main pipe upstream of the cooler at the location of an upstream junction, and a second end connected to the main pipe downstream of the cooler at the site of a downstream junction, characterized in that it further comprises: a proportional type valve positioned on the main pipe, downstream of the downstream junction, between this downstream junction and the intake manifold, this valve being able to proportionally control the total air flow sent to the collector; admission.

The invention will be better understood on reading the description which follows and the examination of the figures which accompany it. These figures are given for illustrative but not limiting of the invention. These figures show:

- Figures la and Ib: a schematic representation of the first embodiment of the invention, for two different modes of operation;

- Figures 2a and 2b: a schematic representation of the second embodiment of the invention, for two different modes of operation.

Identical elements retain the same reference from one figure to another.

Figures 1 show an intake air circuit 1 according to the invention which connects a turbocharger 3 to a diesel engine 2.

More precisely, this engine 2 comprises an intake manifold 2.1 and an exhaust manifold 2.2. The exhaust manifold 2.2 is connected to the turbocharger 3 which comprises a driving turbine 6 and a supercharging turbine 4. The driving turbine 6 drives the supercharging turbine 4 in rotation so that the turbine 4 draws outside air 7 and delivers this pressurized air (supercharging air) into a main duct 8 . This main conduit 8 connects the turbocharger 3 to the intake manifold 2.1. The circulation of the supercharging air in the circuit 1 is represented by arrows.

A charge air cooler 9 is connected in series with the main conduit 8. This cooler 9 cools the charge air by heat exchange with outside air or with engine coolant 2.

Furthermore, a bypass duct 10 allows the supercharging air 5 to bypass the cooler 9. For this purpose, the bypass duct 10 comprises an end 11 connected to the main duct 8 upstream of the cooler 9, at the location a junction 12 upstream. The duct 10 also has an end 13 connected to the main duct 8 downstream of the cooler 9, at the location of a junction 14 downstream.

The exhaust manifold 2.2 is also connected to a recirculation duct 15 which allows recirculation of an exhaust gas portion 26 to the intake manifold 2.1. For this purpose, a first end 16 of the duct 15 is connected to the exhaust manifold 2.2, and a second end 17 of this duct 15 is connected to the duct 10, between the ends 11 and 13 of the duct 10. A valve 18 is mounted on this duct 15 and allows to adjust the flow of exhaust gas 26 to recirculate. A heat exchanger 19 is mounted on the conduit 15, downstream of the valve 18, to cool these exhaust gases.

In order to control the temperature of the gases of the circuit 1, a selection valve 20 controlled by an on-off actuator is connected at the location of the downstream junction 14. This selection valve 20 interconnects, downstream of the cooler 9, the main duct 8 and the downstream end 13 of the duct 10 bypass. This selection valve 20 makes it possible to pass the supercharging air either into the branch duct 10 or into the cooler 9. For this purpose, the valve 20 comprises a flap 20.1 capable of rotating about its axis 20.2. This flap 20.1 is controlled by the on-off type actuator, so that in a first position, the flap 20.1 closes the duct 8 upstream of the junction 14 and in a second position, the shutter 20.1 closes the end 13 of the duct 10. The shutter 20.1 can pass indifferently from one position to another.

In addition, a proportional type valve 21 is mounted on the main duct 8, downstream of the valve 20. More precisely, this valve 21 is mounted on the duct 8, between the valve 20 and the intake manifold 2.1. This valve 21 is controlled by a proportional actuator capable of varying the dimensions of an opening of this valve 20, so that the valve 20 passes or blocks all or part of the gas passing through.

For this purpose, the valve 21 comprises a flap 21.1 rotatable about its axis 21.2 and can take all possible positions between its open position (the flap 21.1 is perpendicular to the duct 8) and its closed position (the flap 21.1 is parallel at line 8). Thus, the flap 21.1 can take a virtually unlimited number of positions, unlike the flap 20.1 which can take only two positions.

The valve 21 thus makes it possible to control, in a proportional manner, the flow rate of all the gases sent to the engine 2, that is to say of the air passing through the main duct 8 and / or the bypass duct 10 as well as exhaust gases passing through the recirculation duct.

The valves 20 and 21 are preferably integrated inside one and the same housing 22 in the most compact manner possible.

In the operating mode of FIG. 1a, the valve 20 directs the supercharging air 5 to the cooler 9. To this end, the shutter 20.1 closes the end 13 of the bypass duct 10. Thus, the supercharging air and, if appropriate, the recirculating exhaust gases 26 are cooled by the cooler 9 and then sent to the intake manifold 2.1. The valve 21 then makes it possible to control the flow rate of the cooled gases sent to the intake manifold 2.1. In the operating mode of FIG. 1b, the valve 20 directs the supercharging air 5 to the bypass duct 10. To this end, the flap 20.1 closes the main duct 8 upstream of the junction 14. Thus, the air 5 of supercharging and, where appropriate, the exhaust gases 26 in recirculation are sent to the intake manifold 2.1, without being cooled by the cooler 9. The valve 21 then controls the flow of uncooled gas sent to the intake manifold 2.1. Thus, whether the charge air is cooled or not, the valve 21 makes it possible to control, with the desired freedom, the total gas flow rate sent to the intake manifold 2.1.

In the embodiment of FIGS. 2, the selection valve 20 is positioned on the junction 12, between the turbocharger 3 and the cooler 9. The valves 20 and 21 are thus positioned inside two distinct modules, so that It is possible to adapt the circuit 1 to motor configurations 2 where the junction 14 is difficult to access. In this embodiment, the flap 20.1 of the valve 20 is controlled by an on-off type actuator, so that in a first position, the flap 20.1 closes the main duct 8 downstream of the junction 12 and in a second position , the flap 20.1 closes the end 11 of the main duct 10. The flap 20.1 can move indifferently from one position to another.

In the operating mode of FIG. 2a, the valve 20 directs the supercharging air 5 to the cooler 9. For this purpose, the valve 20 closes the end 11 of the bypass duct 10. Thus, the charge air is cooled by the cooler 9 and sent to the intake manifold 2.1 together with a portion of the recirculated exhaust gases. The valve 21 then controls the total flow rate of the cooled gases sent to the intake manifold 2.1. In the operating mode of FIG. 2b, the valve 20 directs the air 5 towards the bypass duct 10. For this purpose, the valve 20 closes the main duct 8 at a location downstream of the junction 12 and upstream of the cooler 9. Thus, the supercharging air and, if applicable, the exhaust gases are sent to the intake manifold 2.1 without being cooled by the cooler 9. The valve 21 then controls the total flow of the uncooled gases sent to the intake manifold 2.1. Thus, again, whether the charge air is cooled or not, the valve 21 makes it possible to control, with the desired freedom, the total gas flow rate sent to the intake manifold 2.1.

The choice of one or the other of the embodiments depends, as we have seen, on the conformation of the engine 2, but also on the thermal stresses to which the different parts are subjected. In fact, the valve 20 mounted upstream of the cooler 9 (FIG. 2) is subjected to higher temperatures than those to which the valve 24 mounted downstream of the cooler 9 is subjected. The temperature-sensitive selection valves are thus rather mounted according to the embodiment of FIGS.

The valves 20 and 21 are controlled by means of a control circuit (not shown) taking into account the operating parameters of the motor. In a default operation that can be observed in the event of a malfunction of the control circuit or in the event of a rest (when the valve is not actuated), the valve 20 directs the charge air to the cooler 9. the valve 20 corresponds to the least polluting operating mode of the engine

2.

The actuators that actuate the valves 20 and 21 are of the electric or pneumatic type. Thus, in one example, the on / off actuator of the valve 20 is a jack pneumatic, while the proportional actuator of the valve 21 is a DC motor.

Furthermore, it is possible to mount an inlet air heater in series with the bypass duct, the recirculation duct can then be connected downstream or upstream of this air heater. Such a heater 25 facilitates the regeneration of a particulate filter connected to the output of the engine 2.

Alternatively, as shown in dotted lines 23, the recirculation duct 15 is connected downstream of the valve 21, between this valve 21 and the intake manifold, or directly to the intake manifold 2.1. In this variant, it is possible to control the exhaust gas flow rate independently of the charge air flow rate. In another variant, the first end 16 of the duct 15 is connected downstream of the particulate filter and the second end 17 of the duct 15 is connected upstream of the supercharging turbine 4.

In a variant, the valve 20 is a double-proportional, double-flap valve for independently adjusting the flow rate of the gases passing through the bypass duct 10 and the cooler 9.

Claims

1 - Intake air intake circuit (1) for an internal combustion engine (2), said circuit (1) comprising:

a main air duct (8) interconnecting a turbocharger (3) and an intake manifold (2.1) of the engine, the turbocharger (3) delivering pressurized air to the intake manifold (2.1). via this duct (8) of main air,

a cooler (9) connected in series with the main air duct (8) for cooling the air coming from the turbocharger (3), and

a bypass duct (10) comprising a first end (11) connected to the main duct (8) upstream of the cooler at the location of an upstream junction (12), and a second end (13) connected to the duct ( 8) downstream of the cooler at a downstream junction (14), characterized in that it further comprises:

a proportional-type valve (21) positioned on the main duct (8), downstream of the downstream junction (14), between this downstream junction (14) and the intake manifold (2.1), this valve (21) of proportional type being able to proportionally control the total air flow sent to the inlet manifold (2.1), and

a selection valve (20) controlled by an on-off actuator, this selection valve (20) being mounted on the downstream junction (14) or on the upstream junction (12), this valve

(20) for directing air from the turbocharger (3) to either the cooler (9) or the bypass conduit (10).

2 - intake air circuit according to claim 1, characterized in that: the valve (20) for selection and the proportional valve (21) are positioned inside a single housing (22). 3 - intake air circuit according to claim 1 or 2, characterized in that:

in its default position, the selection valve (20) directs air from the turbocharger (3) to the cooler (9).

4 - intake air circuit according to one of claims 1 to 3, characterized in that it further comprises:

a recirculation duct (15), this recirculation duct (15) having a first end (16) connected to an exhaust manifold (2.2) of the engine and a second end (17) connected to the collector (2.1) of engine intake,

- This recirculation duct (15) for sending a portion of the engine exhaust gas (2) to the intake manifold (2.1) to burn again.

5 - intake air circuit according to claim 4, characterized in that the second end (17) of the recirculation duct (15) is connected to the duct (10) bypass, between the first end (11) and the second end (13) of this duct (10) bypass.

6 - intake air circuit according to claim 4, characterized in that the second end (17) of the recirculation duct (15) is connected to the main duct (8) downstream of the downstream junction (14), between this junction (14) downstream and the intake manifold (2.1), or directly to the intake manifold (2.1).

7 - intake air circuit according to claim 4, characterized in that the first end (16) of the recirculation duct (15) is connected downstream of the particulate filter and the second end (17) of the duct (15). ) recirculation is connected upstream of the turbine (4) supercharging.

8 - intake air circuit according to one of claims 1 to 7, characterized in that it comprises an inlet air heater (25), the heater (25) being mounted in series with the conduit (10) bypass.