FR3101111A1 - Exhaust air injection device - Google Patents

Abstract

Exhaust air injection device System for injecting air (4) to the exhaust for a combustion engine (3), comprising: - an air injection device (17), and - a solenoid valve (20), the air injection device (17) comprising a cylinder head (6) and a cylinder head cover (13), the cylinder head cover comprising a body in which a first air duct is formed (25), the cylinder head comprising a body in which are formed a second air duct (26) and a gas exhaust duct (9), the first air duct (25) being connected upstream to a pump injection air (19), the first air duct (25) being connected downstream to the second air duct (26), the second air duct (26) being connected downstream to the duct exhaust gas (9), the solenoid valve (20) being fixed against the cylinder head cover (13) and connected downstream to the first air duct (25). Figure for the abstract: figure 2

Description

Exhaust air injection device

The invention relates to a device for injecting air into the exhaust for a combustion engine. The invention also relates to an exhaust air injection system for a combustion engine. The invention also relates to a powertrain comprising such an air injection device and/or such an air injection system. The invention finally relates to a motor vehicle comprising such a powertrain and/or such an air injection device and/or such an air injection system.

State of the prior art

Motor vehicle internal combustion engines may have an exhaust air injection system, also referred to as an IAE system or secondary air injection system. The injection of pressurized fresh air into the exhaust ducts of a combustion engine causes combustion in the exhaust ducts of certain residues. This combustion causes an increase in the temperature of the exhaust gases upstream of pollution control devices such as a catalytic converter, a particulate filter, a selective catalytic reduction device. Since these depollution devices are only effective above a certain temperature of the exhaust gases (for example around 400°C), the integration of an air injection system in the exhaust makes it possible to improve their functioning. In particular, when the engine is started, an air injection system at the exhaust accelerates the increase in temperature of a pollution control device, and thus meets pollution standards.

An exhaust air injection system generally consists of an air injection pump pressurizing the air captured at the outlet of an air filter, a solenoid valve controlling the flow of air and an air diffusion system to an exhaust manifold. These systems include many pipes. They are therefore heavy and bulky and their integration into an engine compartment can be tricky. In addition, these systems can easily clog. The interfaces between the many pipes can also generate leaks. Thus the exhaust air injection systems are sometimes unreliable. Finally, the many air ducts cause pressure drops. The pump of an air injection system must therefore be powerful enough to compensate for these pressure drops.

Presentation of the invention

The object of the invention is to provide a device for injecting air into the exhaust remedying the above drawbacks and improving the devices known from the prior art.

More specifically, a first object of the invention is an exhaust air injection device which is particularly light and compact.

A second object of the invention is a device for injecting air into the exhaust which does not clog easily.

A third object of the invention is a device for injecting air into the exhaust which does not cause air leaks or exhaust gas leaks.

A fourth object of the invention is a device for injecting air into the exhaust which generates a minimum pressure drop.

A fifth object of the invention is a device for injecting air into the exhaust which is easily accessible for the purposes of a possible intervention for repair.

The invention relates to an exhaust air injection system for a combustion engine, the air injection system comprising:
- a device for injecting air into the exhaust, and
- a solenoid valve,
the air injection device comprising a cylinder head and a cylinder head cover, the cylinder head cover comprising a body in which a first air duct is formed, the cylinder head comprising a body in which a second air duct is formed and a gas exhaust pipe, the first air pipe being able to be connected upstream to an air injection pump, the first air pipe being connected downstream to the second air pipe, the second air duct being connected downstream to the gas exhaust duct, the solenoid valve being fixed against the cylinder head cover, the solenoid valve being connected downstream to the first air duct.

The air injection system may include a second sealing device between the cylinder head and the cylinder head cover, the second sealing device being adapted to prevent air or exhaust gas leaks from the first conduit air or from the second air line.

The second sealing device may include a metal gasket.

The cylinder head may include a plurality of gas exhaust ducts, and the second air duct may include a chamber and a plurality of air duct portions, each air duct portion being connected upstream to said chamber , and each air duct portion being connected downstream respectively to one of the gas exhaust ducts.

The first air duct can be arranged vertically above the second air duct, and the second air duct can extend the first air duct, the second air duct being arranged vertically above the gas exhaust line, so that a condensate formed in the first air line or in the second air line cannot stagnate in the first air line or in the second air line.

The cylinder head cover may comprise a fixing interface for the solenoid valve, the fixing interface comprising a third sealing device, the third sealing device being intended to prevent air or exhaust gas leaks.

The air injection system may comprise a support for a solenoid valve, said support being fixed directly against the cylinder head cover, the solenoid valve being fixed directly against said support, said support comprising an air collection chamber connected downstream to the first air duct.

The cylinder head cover may include a recess to increase the volume of the air collection chamber.

The air injection system may include a first sealing device between the cylinder head and the cylinder head cover, the first sealing device being adapted to prevent leaks of oil vapor outside a body cylinder head, the first sealing device comprising a resin gasket.

The invention also relates to a powertrain comprising a combustion engine, the combustion engine comprising an air injection system as defined above.

The invention also relates to a motor vehicle comprising an air injection system as defined above, and/or a powertrain as defined above.

Presentation of figures

These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment given on a non-limiting basis in relation to the attached figures, among which:

FIG. 1 is a schematic view of a motor vehicle comprising an exhaust air intake device according to one embodiment of the invention.

FIG. 2 is a side sectional view of a combustion engine fitted with an exhaust air intake device according to one embodiment of the invention.

FIG. 3 is an isometric perspective view of a cylinder head cover of the exhaust air intake device.

Figure 4 is an isometric top view of the cylinder head cover.

Figure 5 is an isometric bottom view of the cylinder head cover.

detailed description

Figure 1 schematically illustrates a motor vehicle 1 equipped with a powertrain 2 according to one embodiment of the invention. The vehicle 1 can be of any kind. In particular, it may for example be a private vehicle, a utility vehicle, a truck or a bus. Powertrain 2 includes a combustion engine 3 and an exhaust air injection system 4.

In the following description, upstream and downstream are defined with reference to the direction of natural flow of air or exhaust gases. Air or exhaust gases flow from upstream to downstream. Moreover, it is considered that the vehicle 1 rests on a horizontal ground. The vertical Z axis is represented by a vector oriented from bottom to top.

The combustion engine 3 comprises an engine block 5 in which are formed cylinders, seats of the combustion of a fuel, for example gasoline or diesel. The cylinders can be any number, for example three cylinders, four cylinders, six cylinders or eight cylinders. The combustion engine 3 also comprises a cylinder head 6 fixed to the engine block 5. The cylinder head 6 is a part of the combustion engine ensuring the high closure of the cylinders. The cylinder head 6 houses or supports in particular air intake valves, exhaust valves 7 as well as camshafts 8 in mechanical connection with the intake valves and the exhaust valves 7. The valves exhaust are mechanical components separating each of the cylinders from a gas exhaust pipe 9. The gas exhaust pipe 9 is a channel formed in the cylinder head to evacuate the exhaust gases, that is to say the gases resulting from the combustion of the fuel in the cylinders. The cylinder head may comprise as many separate gas exhaust pipes 9 as there are cylinders. Each exhaust gas duct conducts exhaust gases from a cylinder to the outside of the cylinder head.

The powertrain also comprises an exhaust device comprising an exhaust manifold 10, for example fixed against the cylinder head at the outlet of the gas exhaust ducts 9. The exhaust manifold may comprise as many inlets as there are exhaust ducts. gas exhaust and a single outlet. It is connected downstream to an exhaust pipe 11, itself connected downstream to a depollution device 12. The depollution device can be, for example, a catalytic converter, a particulate filter, a selective catalytic reduction device (also called SCR device), or any other device capable of purifying or reducing the rate of particles in the exhaust gases. The pollution control device may require the exhaust gases to reach a temperature threshold in order to operate optimally, for example a threshold of approximately 400° C.

The combustion engine 3 also includes a cylinder head cover 13, or cylinder head cover or even cylinder head cap. The cylinder head cover is an upper part of the combustion engine 3 covering the cylinder head 6. As shown in Figure 2, the cylinder head cover 13 can be mounted in vertical support on the cylinder head 6. A substantially horizontal plane P1 can vertically separate the cylinder head cover 13 of the cylinder head 6. The cylinder head 6 can comprise two lower half-bearings 14 and the cylinder head cover 13 can comprise two upper half-bearings 15. The two lower half-bearings 14 cooperate with the two upper half-bearings 15 to form two bearings supporting two camshafts. The assembly formed by the cylinder head 6 and the cylinder head cover 13 forms a sealed interior volume 16 in which the camshafts 8 and the valves 7 can be arranged in particular. Oil, in the form of vapor or droplets, can be located in this interior volume 16 in order to lubricate various moving parts of the combustion engine, in particular in order to lubricate the camshafts and the valves.

The cylinder head and the cylinder head cover can be one-piece parts. They can be made of metal. They can be obtained by machining and/or by foundry. The cylinder head cover is fixed in leaktight manner to the cylinder head, for example by means of fixing screws. As visible in Figures 3, 4 and 5 the cylinder head and the cylinder head cover may further comprise stiffening ribs, openings intended to accommodate, for example, injectors and/or spark plugs.

The exhaust air injection system 4 comprises an air injection device 17 formed in the cylinder head 6 and the cylinder head cover 13. It also comprises an air filter 18, an injection pump 19, and a solenoid valve 20. The air filter 18 is connected downstream to the air injection pump 19 by a first external pipe 21. The air injection pump 19 is connected downstream to the solenoid valve 20 via a second external pipe 22.

The air filter 18 is a device capable of taking fresh air from outside and filtering it. In particular, it can filter particles suspended in the air to prevent them from entering the air injection system at the exhaust. The air filter 18 can also be used to filter the fresh air which is supplied to the cylinders via intake ducts to allow fuel combustion.

The air injection pump 19, or more simply air pump 19, is a pump capable of putting the air coming from the air filter 18 under pressure. It can be electrically connected to a source of electrical energy and to an electronic control unit. Its activation can be controlled by control commands issued by the electronic control unit.

The solenoid valve 20 is a device capable of controlling the flow of air passing through it. It may include a connector electrically connected to the electronic control unit. Control commands issued by the electronic control unit make it possible to control the flow of air passing through the solenoid valve. It is fixed to the cylinder head cover 13 via a support 23. The support 23 is fixed, for example screwed, directly against the cylinder head cover and the solenoid valve is fixed, for example screwed directly against the support 23. The support 23 is fixed on a fixing interface 24 of the cylinder head cover clearly visible in FIG. 4. The solenoid valve is thus firmly held against the combustion engine 3, without overhang. Such fixing of the solenoid valve is particularly reliable and resistant to vibrations. The support 23 comprises an air collection chamber connected downstream to the air injection device 17. The support 23 may also comprise a channel connected upstream to the air collection chamber and downstream to the injection device. injection of air 17, in particular to a first air duct 25 formed in the cover of the cylinder head. Alternatively the support 23 and the cylinder head cover could form a single piece. In other words, the solenoid valve could be fixed directly against the cylinder head cover.

The cylinder head cover may also include a recess so as to save material and increase the volume of the collection chamber. This recess can advantageously be positioned below the solenoid valve 20.

We will now describe in more detail the air injection device 17, that is, a part of the exhaust air injection system 4 formed in the body of the combustion engine.

The cylinder head cover 13 comprises a body in which the first air duct 25 is formed. Similarly, the cylinder head comprises a body in which a second air duct 26 and the gas exhaust duct 9 are formed. first air duct 25 and the second air duct are therefore recesses made respectively in the body of the cylinder head cover 13 and in the body of the cylinder head 6. The first air duct 25 is connected (i.e. that is to say butted) downstream to the second air duct 26. The second air duct 26 is connected downstream to the gas exhaust duct 9.

The first air duct 25 therefore comprises an inlet which can be arranged on an upper face of the cylinder head cover and an outlet which can be arranged on a lower face of the cylinder head cover, the lower face being in contact with the cylinder head 6. By traversing the first air duct from its inlet to its outlet, that is to say from upstream to downstream, it is observed that it follows a downward trajectory, even locally horizontal.

Similarly, the second air duct 26 comprises an inlet arranged on an upper face of the cylinder head and an outlet which can be arranged on a side face of the cylinder head. By traversing the second air duct from its inlet to its outlet, that is to say from upstream to downstream, it can be seen that it follows an equally downward trajectory, even locally horizontal.

The first air duct 25 is arranged above the second air duct 26. The second air duct extends the first air duct 25 and is arranged above the gas exhaust duct 9 Thus, a liquid or a condensate formed in the first air duct cannot stagnate there and is evacuated by gravity towards the second air duct. Similarly, a liquid or a condensate formed in the second air duct cannot stagnate there and is evacuated by gravity towards the gas exhaust duct 9. In other words, neither the first air duct 25 nor the second air duct 26 does not include a low point forming a retention volume for a liquid. The orientation of the first air duct and the second air duct could be made as vertical as possible to promote gravity flow of any liquid or condensate to the exhaust duct.

Referring to Figures 1, 2 and 5 the assembly formed by the cylinder head and the cylinder head cover comprises a first sealing device 31 and a second sealing device 32, both arranged between the cylinder head and the cylinder head cover along the plane P1. The first sealing device is capable of preventing oil vapor leaks outside the assembly formed by the cylinder head and the cylinder head cover. The first sealing device can be arranged around the interior volume 16, in which the lubricating oil can be under pressure. The second sealing device is capable of preventing air or exhaust gas leaks from the first air duct or from the second air duct of the air injection device. It is arranged around the interface formed between the first air duct and the second air duct. It may have a shape substantially reproducing the shape of a section of the first air duct and of the second air duct, for example a globally circular or globally rectangular shape.

The two sealing devices are therefore subject to different constraints. The first device is designed to withstand an environment laden with lubricating oil, and the second device is designed to withstand pressurized air from upstream or possibly high temperature exhaust gases which occasionally rose upstream from the gas exhaust pipe 9. Advantageously, the first sealing device 31 may comprise a resin seal. The second sealing device may include a metal seal. In a variant embodiment, the air injection device could comprise a single sealing device that is simultaneously resistant to oil, pressurized air and exhaust gases. This single sealing device could for example be a metal gasket. However, a single sealing device would be more complex and more expensive to implement than two separate sealing devices of a different nature.

Referring to Figure 4, the housing cover further comprises a third sealing device 33 arranged on the attachment interface 24 for the support 23 holding the solenoid valve 20. Analogously to the second sealing device, the The third sealing device 33 is designed to resist pressurized air coming from upstream or possibly exhaust gases which occasionally rise upstream from the gas exhaust pipe 9. The third sealing device may include a metal gasket.

The system for injecting air into the exhaust thus constituted makes it possible to economize on an air line compared to the systems for injecting air into the exhaust known from the state of the art. Indeed, with the system according to the invention, there is no need to provide a pipe between the solenoid valve 20 and the cylinder head cover. This saves space in the engine compartment in which the combustion engine is positioned. In addition, the pipes formed by the air ducts 25 and 26 participate in lightening the combustion engine.

Referring to Figure 2, the combustion engine 3 can be positioned at a short distance from a bonnet 34 of the vehicle. The solenoid valve can be positioned so as to be directly accessible under the bonnet 34 of the vehicle. Its maintenance and/or possible replacement is thus facilitated.

When the combustion engine is running, fresh air is sucked in from outside by the air injection pump. The fresh air enters the air injection system at the exhaust 4 through the air filter 18, it then passes through the first external pipe 21, then the air injection pump 19. The air is pressurized by the air injection pump 19, it crosses the second external pipe 22, then reaches the solenoid valve 20. Depending on the state of the solenoid valve controlled by the electronic control unit, the air flow through the solenoid valve 20 can be adjusted. It then passes through the support 23 and then arrives in the air injection device at the level of the cylinder head cover 13. Thanks to the third sealing device 33, no air or exhaust gas leak occurs at the interface between the support 23 and the cylinder head cover. The air then passes through the first air duct 25 and reaches the second air duct 26 integrated into the cylinder head. Thanks to the second sealing device 32, no air or exhaust gas leak occurs at the interface between the first air duct and the second air duct. The air then arrives in the chamber 27 from which it is distributed in the air duct portions 28. The air is then injected into the gas exhaust ducts 9 as close as possible to the exhaust valves 7. The path of the air from the outside to the gas exhaust ducts offers a low pressure drop and good distribution homogeneity in the various gas exhaust ducts 9. The air thus mixed with the exhaust gas exhaust allows the combustion of the residues present in the exhaust gases. The temperature of the exhaust gases can thus increase rapidly, as soon as the combustion engine is started. The exhaust gases are then evacuated from the combustion engine 3 via the exhaust manifold 10, the exhaust pipe 11 and the pollution control unit 12. The exhaust gases having reached a high temperature, the pollution control unit can function optimally. The exhaust gases thus treated can then be evacuated from the vehicle. When condensate forms in the exhaust air injection system, it is guided by gravity to the gas exhaust line 9. It therefore cannot stagnate or accumulate in the one in the exhaust air injection system lines. Along with this operation, the various moving parts within the cylinder head 6 can be lubricated with pressurized oil. The pressurized oil does not escape through the interface between the cylinder head cover and the cylinder head thanks to the first sealing device 31.

Claims (11)

Exhaust air injection system (4) for a combustion engine (3), characterized in that it comprises:
- an air injection device (17), and
- a solenoid valve (20),
the air injection device (17) comprising a cylinder head (6) and a cylinder head cover (13), the cylinder head cover comprising a body in which a first air duct (25) is formed, the cylinder head comprising a body in which a second air duct (26) and a gas exhaust duct (9) are formed, the first air duct (25) being able to be connected upstream to a fuel injection pump air (19), the first air duct (25) being connected downstream to the second air duct (26), the second air duct (26) being connected downstream to the exhaust duct of the gas (9), the solenoid valve (20) being fixed against the cylinder head cover (13), the solenoid valve (20) being connected downstream to the first air duct (25).
Air injection system (4) according to the preceding claim, characterized in that it comprises a second sealing device (32) between the cylinder head (6) and the cylinder head cover (13), the second sealing device the seal being capable of preventing air or exhaust gas leaks from the first air duct or from the second air duct.
Air injection system (4) according to the preceding claim, characterized in that the second sealing device (32) comprises a metal seal.
Air injection system (4) according to one of the preceding claims, characterized in that the cylinder head (6) comprises a plurality of gas exhaust ducts (9), and in that the second exhaust duct air (26) comprises a chamber (27) and a plurality of portions of air ducts (28), each portion of air duct (28) being connected upstream to said chamber (27), and each portion of duct air being connected downstream respectively to one of the gas exhaust pipes (9).
Air injection system (4) according to one of the preceding claims, characterized in that the first air duct (25) is arranged vertically above the second air duct (26), and in that the second air duct (26) extends the first air duct (25), the second air duct (26) being arranged vertically above the gas exhaust duct (9), so that a condensate formed in the first air duct (25) or in the second air duct (26) cannot stagnate in the first air duct or in the second air duct.
Air injection system (4) according to one of the preceding claims, characterized in that the cylinder head cover (13) comprises a fixing interface (24) for the solenoid valve (20), the fixing interface (24 ) comprising a third sealing device (33), the third sealing device being intended to prevent air or exhaust gas leaks.
Air injection system (4) according to one of the preceding claims, characterized in that it comprises a support (23) for the solenoid valve, the said support (23) being fixed directly against the cylinder head cover (13), the solenoid valve (20) being fixed directly against the said support (23), the said support comprising an air collection chamber connected downstream to the first air conduit (25).
Air injection system (4) according to the preceding claim, characterized in that the cylinder head cover comprises a recess to increase the volume of the air collection chamber.
Air injection system (4) according to one of the preceding claims, characterized in that it comprises a first sealing device (31) between the cylinder head (6) and the cylinder head cover (13), the a first sealing device being adapted to prevent leakage of oil vapor outside a cylinder head body (6), the first sealing device (31) comprising a resin gasket.
Powertrain (2) characterized in that it comprises a combustion engine (3), the combustion engine (3) comprising an air injection system (4) according to one of the preceding claims.
Motor vehicle (1), characterized in that it comprises an air injection system (4) according to one of the preceding claims, and/or a powertrain (2) according to the preceding claim.