DE202016105725U1 - Supercharged internal combustion engine with compressor, exhaust gas recirculation and valve unit - Google Patents

Abstract

A supercharged internal combustion engine comprising - an intake system (1) for supplying a charge air flow, - an exhaust gas removal system for discharging exhaust gas, - at least one compressor (2) arranged in the intake system (1) and having at least one in a housing (2c) on a rotatable shaft (2d) mounted impeller (2e) is equipped, - an exhaust gas recirculation (5) comprising a return line (5a), which branches off from the Abgasabführsystem and upstream of the at least one impeller (2e) to form a node (5b) in the intake system (1) and a valve unit (3) arranged at the junction (5b) in the intake system (1) and comprising a valve housing (3d) and a valve (3a) arranged in the valve housing (3d), the valve (3a) being around one transverse to the fresh air flow axis (3b) is pivotable in the manner that the flap (3a) in a first end position with a front side (3a ') blocks the intake system (1) and the Rüc kführleitung (5a) releases and in a second end position with a rear side (3a'') the return line (5a) covered and the intake system (1) releases, characterized in that - the valve housing (3d) at least partially with a thermal insulation (4) is provided.

Description

• – einem Ansaugsystem zum Zuführen einer Ladeluftströmung,
• – einem Abgasabführsystem zum Abführen von Abgas,
• – mindestens einem im Ansaugsystem angeordneten Verdichter, der mit mindestens einem in einem Gehäuse auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist,
• – einer Abgasrückführung umfassend eine Rückführleitung, die vom Abgasabführsystem abzweigt und stromaufwärts des mindestens einen Laufrades unter Ausbildung eines Knotenpunktes in das Ansaugsystem mündet, und
• – einer am Knotenpunkt im Ansaugsystem angeordneten Ventileinheit, die ein Ventilgehäuse und eine in dem Ventilgehäuse angeordnete Klappe umfasst, wobei die Klappe um eine quer zur Frischluftströmung verlaufende Achse in der Art verschwenkbar ist, dass die Klappe in einer ersten Endposition mit einer Vorderseite das Ansaugsystem versperrt und die Rückführleitung freigibt und in einer zweiten Endposition mit einer Rückseite die Rückführleitung verdeckt und das Ansaugsystem freigibt.

The invention relates to a supercharged internal combustion engine with

• An intake system for supplying a charge air flow,
• An exhaust gas removal system for removing exhaust gas,
• At least one compressor arranged in the intake system and equipped with at least one impeller mounted in a housing on a rotatable shaft,
• An exhaust gas recirculation system comprising a return line which branches off from the exhaust gas removal system and opens into the intake system upstream of the at least one impeller, forming a junction, and
• A valve unit arranged at the nodal point in the intake system, comprising a valve housing and a flap arranged in the valve housing, wherein the flap is pivotable about an axis extending transversely to the fresh air flow in such a way that the flap blocks the intake system with a front side in a first end position and the return line releases and in a second end position with a back cover the return line and the intake system releases.

An internal combustion engine of the type mentioned is used as a motor vehicle drive. In the context of the present invention, the term internal combustion engine includes diesel engines and gasoline engines, but also hybrid internal combustion engines that use a hybrid combustion process, as well as hybrid drives, which in addition to the internal combustion engine include an electric motor that can be connected to the engine, which receives power from the internal combustion engine or as switchable auxiliary drive additionally delivers power.

In recent years, there has been a shift toward supercharged engines, with the economic importance of these engines for the automotive industry continuing to increase.

Charging is primarily a performance enhancement process in which the air needed for the engine combustion process is compressed, allowing each cylinder to be supplied with greater air mass per cycle. As a result, the fuel mass and thus the medium pressure can be increased.

The charge is a suitable means to increase the capacity of an internal combustion engine with unchanged displacement or to reduce the displacement at the same power. In any case, the charging leads to an increase in space performance and a lower power mass. If the displacement is reduced, then the load spectrum can be shifted to higher loads, where the specific fuel consumption is lower. By charging in combination with a suitable transmission design and a so-called downspeeding can be realized, in which also a lower specific fuel consumption can be achieved.

Charging thus supports the constant effort in the development of internal combustion engines to minimize fuel consumption, d. H. to improve the efficiency of the internal combustion engine.

Frequently, an exhaust gas turbocharger is used for charging, in which a compressor and a turbine are arranged on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in the turbine, causing the shaft to rotate. The energy emitted by the exhaust gas flow to the turbine and finally to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor conveys and compresses the charge air supplied to it, whereby a charging of the cylinder is achieved. Advantageously, a charge air cooler is provided downstream of the compressor in the intake system, with which the compressed charge air is cooled before entering the at least one cylinder. The radiator lowers the temperature and thus increases the density of the charge air, so that the cooler to a better filling of the cylinder, d. H. contributes to a larger air mass. There is a compaction by cooling.

The advantage of an exhaust gas turbocharger in comparison to a - drivable by auxiliary drive - loader is that an exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases, while a loader requires the energy required for its drive directly or indirectly from the internal combustion engine and thus, at least as long as the drive power does not come from an energy recovery, adversely affects the efficiency, d. H. decreases.

If it is not an electric machine, d. H. electrically drivable charger is regularly a mechanical or kinematic connection for power transmission between the charger and the internal combustion engine is required, which also affects the packaging in the engine compartment.

The advantage of a supercharger over an exhaust gas turbocharger is that the supercharger can always generate and provide the required boost pressure, regardless of the operating state of the internal combustion engine. This is especially true for a loader by means of Electric machine is electrically driven and therefore independent of the speed of the crankshaft.

In fact, according to the state of the art, it is difficult to increase the power by means of turbocharging in all engine speed ranges. It is observed a greater torque drop when falling below a certain speed. This torque drop becomes understandable if it is taken into account that the boost pressure ratio depends on the turbine pressure ratio or the turbine output. If the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a smaller turbine pressure ratio or a smaller turbine power. Consequently, the boost pressure ratio also decreases toward lower speeds. This is synonymous with a torque drop.

The internal combustion engine, which is the subject of the present invention, has a compressor for charging, wherein in the context of the present invention the term compressor can be subsumed both by a supercharger drivable by means of an auxiliary drive and by a compressor of an exhaust gas turbocharger.

Another fundamental goal is to reduce pollutant emissions. In solving this problem, charging may also be useful. With targeted design of the charge namely benefits in efficiency and in the exhaust emissions can be achieved. In order to comply with future limits for pollutant emissions in addition to the charge but further action is required.

Thus, the exhaust gas recirculation serves to reduce nitrogen oxide raw emissions. The recirculation rate x _{AGR is} determined to be x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR designates} the mass of recirculated exhaust gas and m _{fresh air} the fresh air supplied. Any oxygen or recirculated air returned via exhaust gas recirculation must be taken into account.

The supercharged by means of compressor internal combustion engine according to the invention is equipped with at least one exhaust gas recirculation, wherein the recirculating from the Abgasabführsystem return line opens to form a node upstream of the compressor in the intake system, as is the case regularly in a low-pressure EGR, the exhaust gas on the Returned inlet side, which has already flowed through a arranged in Abgasabführsystem turbine. For this purpose, the low-pressure EGR comprises a return line, which branches off downstream of the turbine from the Abgasabführsystem and preferably opens upstream of the compressor in the intake system.

The internal combustion engine, which is the subject of the present invention, furthermore has a valve unit, which is arranged in the intake system at the junction. The valve unit comprises a valve housing and a valve disposed in the valve housing. The flap can serve to adjust the amount of fresh air supplied via the intake system and at the same time meter the amount of exhaust gas recirculated via exhaust gas recirculation and is pivotable about an axis extending transversely to the fresh air flow such that in a first end position the front of the flap obstructs the intake system and at the same time the return line is released and in a second end position, the back of the flap covers the return line and at the same time the intake system is released. In the above sense, both obstructing and concealing do not necessarily mean closing or completely obstructing and concealing.

The transverse to the fresh air flow axis about which the flap is pivotable, does not have to be a figurative axis. Rather, this axis may be a virtual axis, the position of which may also have a small clearance with respect to the rest of the intake system, the storage being carried out in a different way.

Problems may arise with the exhaust gas recirculation switched on when exhaust gas is introduced upstream of the compressor into the intake system. It can form condensate. There are several scenarios of relevance.

On the one hand, condensate can form when recirculated hot exhaust gas meets cool fresh air and is mixed. The exhaust gas cools, whereas the temperature of the fresh air is raised. The temperature of the mixture of fresh air and recirculated exhaust gas, d. H. the charge air temperature is below the exhaust gas temperature of the recirculated exhaust gas. As part of the cooling of the exhaust gas previously contained gaseous substances contained in the exhaust gas, in particular water, condense when the taut temperature of a component of the gaseous charge air flow is exceeded.

It comes to a condensation in the free charge air flow, often impurities in the charge air form the starting point for the formation of condensate droplets.

On the other hand, condensate may form when hot exhaust gas or the charge air impinges on the inner wall of the intake system or on the inner wall of the valve housing, since the wall temperature is usually below the taut temperature of the relevant gaseous components. In this context, the valve body comes as Part of the intake system is of particular importance, because the valve body is regularly acted upon even when the exhaust gas recirculation is switched off with exhaust gas. The existing or standing in the valve housing exhaust gas cools due to heat conduction, which can form condensate on the exposed to exhaust gas inside the valve housing, which collects in the valve housing and when switching, ie activating the exhaust gas recirculation is suddenly introduced into the intake system.

The problem of condensate formation is exacerbated with increasing recirculation rate, since with the increase in the amount of recirculated exhaust gas, the proportions of the individual exhaust gas components in the charge air inevitably increase, in particular the proportion of water contained in the exhaust gas. According to the prior art, therefore, the amount of exhaust gas recirculated by means of low-pressure EGR is often limited in order to prevent or reduce the condensation out. The necessary limitation of the low-pressure EGR on the one hand and the high exhaust gas recirculation rates required for a significant reduction of the nitrogen oxide emissions on the other hand lead to different objectives in the dimensioning of the recirculated exhaust gas quantity. The legal requirements for the reduction of nitrogen oxide emissions illustrate the high relevance of this problem in practice.

Condensate and condensate droplets are undesirable and lead to increased noise in the intake system, possibly damaging the blades of the at least one compressor impeller. The latter is associated with a reduction in the efficiency of the compressor.

Against this background, it is the object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, with which the disadvantages known from the prior art are overcome and with the particular damage to the compressor due to condensation is counteracted.

• – einem Ansaugsystem zum Zuführen einer Ladeluftströmung,
• – einem Abgasabführsystem zum Abführen von Abgas,
• – mindestens einem im Ansaugsystem angeordneten Verdichter, der mit mindestens einem in einem Gehäuse auf einer drehbaren Welle gelagerten Laufrad ausgestattet ist,
• – einer Abgasrückführung umfassend eine Rückführleitung, die vom Abgasabführsystem abzweigt und stromaufwärts des mindestens einen Laufrades unter Ausbildung eines Knotenpunktes in das Ansaugsystem mündet, und
• – einer am Knotenpunkt im Ansaugsystem angeordneten Ventileinheit, die ein Ventilgehäuse und eine in dem Ventilgehäuse angeordnete Klappe umfasst, wobei die Klappe um eine quer zur Frischluftströmung verlaufende Achse in der Art verschwenkbar ist, dass die Klappe in einer ersten Endposition mit einer Vorderseite das Ansaugsystem versperrt und die Rückführleitung freigibt und in einer zweiten Endposition mit einer Rückseite die Rückführleitung verdeckt und das Ansaugsystem freigibt,

die dadurch gekennzeichnet ist, dass

• – das Ventilgehäuse zumindest bereichsweise mit einer Wärmeisolierung versehen ist.

This problem is solved by a supercharged internal combustion engine

• An intake system for supplying a charge air flow,
• An exhaust gas removal system for removing exhaust gas,
• At least one compressor arranged in the intake system and equipped with at least one impeller mounted in a housing on a rotatable shaft,
• An exhaust gas recirculation system comprising a return line which branches off from the exhaust gas removal system and opens into the intake system upstream of the at least one impeller, forming a junction, and
• A valve unit arranged at the nodal point in the intake system, comprising a valve housing and a flap arranged in the valve housing, wherein the flap is pivotable about an axis extending transversely to the fresh air flow in such a way that the flap blocks the intake system with a front side in a first end position and the return line releases and in a second end position with a rear side covers the return line and releases the intake system,

which is characterized in that

• - The valve housing is at least partially provided with a thermal insulation.

The valve housing of the internal combustion engine according to the invention has at least partially on a thermal insulation. The thermal insulation should counteract the formation of condensation in the valve housing and reduce or prevent the formation of condensation.

For this purpose, the valve housing - at least partially - provided with a thermal insulation, d. H. coated, clad, treated or the like. In the context of the present invention, a heat insulation is characterized in that the heat insulation has a low thermal conductivity, in particular a lower thermal conductivity than a base material optionally used for the valve housing.

The cooled by the cooler ambient air on the outside valve housing removes heat from the hot in the valve housing exhaust heat due to heat conduction, the heat insulation according to the invention as a barrier to reduce or hinder this heat conduction, which in turn counteracts the formation of condensate.

According to the invention, the heat insulation thus serves as a thermal barrier, by which the heat permeability of the valve housing is reduced. By this measure, the amount of heat dissipated from the inside of the valve housing via housing walls to the outside of the valve housing should be reduced in an advantageous manner.

To form a valve housing according to the invention may also serve a conventional valve housing, which is extended or modified in the context of post-processing or retrofitting to a valve housing according to the invention.

The risk of damage to the compressor due to condensate droplets is caused by the Use of a inventively designed valve housing reduced.

Thus, the object underlying the invention is achieved, namely provided a supercharged internal combustion engine, with which the known from the prior art disadvantages are overcome and with the particular damage to the compressor due to condensation is counteracted.

As part of the exhaust gas recirculation, preferably exhaust gas is passed through the compressor, which has been subjected to exhaust gas aftertreatment, in particular in a particle filter. In this way, deposits in the compressor, which change the geometry of the compressor, in particular the flow cross-sections, and worsen the efficiency of the compressor, can be avoided.

Further advantageous embodiments of the supercharged internal combustion engine are discussed in connection with the subclaims.

Advantageous embodiments of the supercharged internal combustion engine, in which the axis near the edge, d. H. is arranged near an edge portion of the flap. In this embodiment, the flap is similar to a door mounted laterally and pivotally, namely at one of its edges. This distinguishes the flap of the invention of centrally mounted shut-off elements or flaps such as a butterfly valve.

Advantageous embodiments of the supercharged internal combustion engine, in which the axis near the wall, d. H. is arranged near a wall portion of the intake system. The intake system regularly takes over the function of a frame with respect to the flap, d. H. framed the flap. As such, an embodiment in which the axis is located near an edge portion of the flap is also typically an embodiment in which the axis is located near a wall portion of the aspiration system. The essential advantage of both embodiments is that the flap is positioned close to the wall in the second end position, so that a completely free passage for the fresh air is created.

Advantageous embodiments of the supercharged internal combustion engine, in which the valve housing is provided to more than 40% with a thermal insulation.

Advantageous embodiments of the supercharged internal combustion engine, in which the valve housing is provided with more than 60% with a thermal insulation.

Embodiments of the supercharged internal combustion engine in which the valve housing is provided with more than 80% heat insulation are particularly advantageous.

Particularly advantageous embodiments of the supercharged internal combustion engine, in which the valve housing is completely or almost completely provided with a heat insulation.

The more extensive the valve housing is heat-insulated, the more effective the thermal insulation can fulfill its function as a thermal barrier and the more effective the formation of condensation is counteracted.

Embodiments of the supercharged internal combustion engine in which the thermal insulation comprises plastic are advantageous.

Embodiments of the supercharged internal combustion engine in which the thermal insulation comprises ceramic are advantageous.

Embodiments of the supercharged internal combustion engine in which the thermal insulation comprises enamel are advantageous.

Plastic, ceramic and enamel and the like are characterized by a low thermal conductivity, so that these materials are particularly suitable for the formation of a thermal insulation to prevent condensation in the valve housing.

Embodiments of the supercharged internal combustion engine in which the thermal insulation is at least also formed by means of surface treatment are advantageous. For the formation of the thermal insulation can also first material, such as enamel or ceramic or the like, are introduced and then surface-treated. Optionally, the thermal insulation is formed exclusively by means of surface treatment.

Advantageous embodiments of the supercharged internal combustion engine, in which the heat insulation is formed at least by using different materials for the valve housing, in the way that one material has a thermal conductivity λ _low and another material has a thermal conductivity λ _high , where: λ _low < λ _high .

Embodiments of the supercharged internal combustion engine in which the thermal insulation is at least one in a cavity are advantageous includes located gas cushion. The gas cushion or air cushion serves as a heat barrier, whereby the thermal conductivity or the heat permeability of the valve housing is reduced.

In the present case, the cavity does not have to be a hermetically sealed room. The gas cushion can also fill a recess or undercut of a double-walled valve housing which is open towards the edges. Preferably, however, the cavity is a closed space from which the air can not escape. Instead of air, any other gas or a liquid or the like may be used, for example Styrofoam or the like.

Embodiments of the supercharged internal combustion engine in which the valve housing has a modular design are advantageous. In particular, when the thermal insulation or the valve housing comprises a cavity located in an air cushion or the like and / or is made of several different materials, a modular construction of the valve housing is suitable.

Embodiments of the supercharged internal combustion engine in which the at least one cavity is at least also formed using shuttering elements are advantageous, wherein the shuttering elements serve to form an at least partially double-walled valve housing and thus the formation of the at least one cavity.

In principle, embodiments of the supercharged internal combustion engine in which the valve housing is at least partially double-walled, whereby the at least one cavity is formed at least with advantage, are advantageous.

In this context, embodiments of the supercharged internal combustion engine in which the at least one cavity is also formed using shuttering elements arranged at a distance from one another are advantageous, wherein inner shuttering elements form a permanently exhaust-gas-conducting system and outer shuttering elements arranged at a distance from the inner shuttering elements form the at least one to serve a cavity.

The valve housing may be a system constructed of sheet metal, for example, in which the at least one cavity is formed in the course of the assembly by using shuttering elements arranged at a distance from one another. Cast parts or other components may or may not be attached to this valve housing.

The valve housing may also be a casting or monolithic component, in which the at least one cavity is incorporated as part of the casting process or manufacturing process as an integral part. A monolithic component can also be manufactured by means of 3D printing.

Embodiments of the supercharged internal combustion engine in which the heat insulation forms an inner side of the valve housing which is exposed to exhaust gas are at least advantageous.

Embodiments of the supercharged internal combustion engine may also be advantageous in which the thermal insulation forms at least one outer side of the valve housing which is not exposed to exhaust gas.

In contrast to a valve housing, in which the heat insulation is provided on the inside, the hot exhaust gas in a valve housing, in which the heat insulation is provided on the outside, must first heat or warm the hot exhaust gas loaded inner walls of the valve housing before the provided on the outside thermal insulation can act as a thermal barrier.

Embodiments of the supercharged internal combustion engine in which at least one exhaust-gas turbocharger is provided, which comprises a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system, are advantageous. With regard to the above embodiment, reference is made to the statements already made in connection with the exhaust gas turbocharger, in particular the advantages that have been pointed out.

In this connection, therefore, embodiments of the supercharged internal combustion engine in which the at least one compressor is the compressor of the at least one exhaust gas turbocharger are also advantageous.

Embodiments of the supercharged internal combustion engine in which the at least one compressor is a radial compressor are advantageous. This embodiment allows a dense packaging in terms of charging. The compressor housing can be designed as a spiral or worm housing. In an exhaust gas turbocharger, the deflection of the charge air flow in the compressor of the exhaust gas turbocharger can advantageously be used to guide the compressed charge air to the inlet side by the shortest route from the outlet side, on which the turbine of the exhaust gas turbocharger is frequently arranged.

In this context, embodiments are advantageous in which the turbine of the at least one exhaust-gas turbocharger is a radial turbine. This embodiment also allows a tight packaging of the exhaust gas turbocharger and thus the overall charge.

Unlike the turbines, compressors are defined by their outflow. A radial compressor is thus a compressor whose outflow from the blades takes place substantially radially. In the context of the present invention, essentially radial means that the velocity component in the radial direction is greater than the axial velocity component.

But can also be advantageous embodiments of the supercharged internal combustion engine, in which the at least one compressor is designed in Axialbauweise. The outflow from the impeller blades of an axial compressor takes place substantially axially.

Embodiments of the supercharged internal combustion engine in which the at least one compressor has an inlet region which runs and is coaxial with the shaft of the at least one impeller are advantageous, so that the inflow of the charge air to the at least one impeller takes place essentially axially.

In an axial flow of the compressor often eliminates a deflection or change in direction of the charge air flow in the intake upstream of the at least one impeller, whereby unnecessary pressure losses in the charge air flow due to flow deflection can be avoided and the pressure of the charge air is increased at the inlet to the compressor. The lack of change in direction also reduces the contact of the exhaust gas or the charge air with the inner wall of the intake system or with the inner wall of the compressor housing and thus reduces the heat transfer and condensation.

When using at least one exhaust gas turbocharger embodiments of the supercharged internal combustion engine are advantageous in which the return line branches off from the Abgasabführsystem downstream of the turbine of the at least one exhaust gas turbocharger according to a low-pressure EGR.

In contrast to a high pressure EGR, which introduces exhaust gas taken from the exhaust system upstream of the turbine into the intake system, preferably downstream of the compressor, at low pressure EGR exhaust is recirculated to the inlet side which has already passed through the turbine. For this purpose, the low-pressure EGR comprises a return line, which branches off downstream of the turbine from the Abgasabführsystem and opens upstream of the compressor in the intake system.

The main advantage of the low-pressure EGR compared with the high-pressure EGR is that the exhaust gas flow introduced into the turbine is not reduced by the amount of recirculated exhaust gas in the case of exhaust gas recirculation. It is always the entire exhaust gas flow to the turbine to generate a sufficiently high boost pressure available.

The exhaust gas, which is returned to the inlet side by means of low-pressure EGR and is preferably cooled, is mixed with fresh air upstream of the compressor. The thus generated mixture of fresh air and recirculated exhaust gas forms the charge air or combustion air, which is supplied to the compressor and compressed.

Embodiments of the supercharged internal combustion engine in which a first shut-off element in the exhaust-gas removal system is arranged downstream of the branch of the return line are advantageous. The first shut-off element can be used to increase the exhaust gas pressure upstream of the shut-off element in the exhaust gas discharge system, and thus be used for an increase in the pressure gradient between the Abgasabführsystem and the intake system. This offers particular advantages at high recirculation rates, which require a larger pressure gradient.

Also advantageous are embodiments of the supercharged internal combustion engine in which a second shut-off element is arranged in the intake system upstream of the junction. The second shut-off element is used on the inlet side to reduce the pressure in the intake system and thus - as the first shut-off - contribute to an increase in the pressure gradient between the Abgasabführsystem and the intake system.

In this context, embodiments of the supercharged internal combustion engine in which the first and / or the second shut-off element is a pivotable or rotatable flap are advantageous.

In order to improve the torque characteristic of the supercharged internal combustion engine, it may be advantageous to provide two or more exhaust gas turbochargers, for example a plurality of exhaust gas turbochargers connected in series. By switching in series of two exhaust gas turbochargers, one of which is an exhaust gas turbocharger as a high pressure stage and an exhaust gas turbocharger as a low pressure stage, the compressor map can be widened in an advantageous manner, both towards smaller compressor streams as well as towards larger compressor streams.

In particular, in the case of the exhaust gas turbocharger serving as a high-pressure stage, the pumping limit can be shifted towards smaller compressor flows, which means that high boost pressure ratios can be achieved even with small compressor flows, which significantly improves the torque characteristic in the lower rpm range. This is achieved by designing the high-pressure turbine for small exhaust gas mass flows and providing a bypass line, with which increasing exhaust gas mass flow increasingly exhaust gas is passed to the high-pressure turbine.

The torque characteristic may be further characterized by a plurality of turbochargers arranged in parallel, i. H. be improved by a plurality of parallel turbines with a smaller turbine cross-section, with turbines are switched successively with increasing exhaust gas.

Moving the surge line towards smaller charge air flows is also possible with turbochargers arranged in parallel, so that sufficiently high boost pressures can be provided for small quantities of charge air in order to ensure a satisfactory torque characteristic of the internal combustion engine at low speeds.

Furthermore, the response of such a supercharged engine is significantly improved over a comparable internal combustion engine having a single exhaust gas turbocharger because the smaller turbines are less sluggish and the rotor of a smaller sized turbine and a smaller sized compressor can be accelerated faster.

Advantageous embodiments of the supercharged internal combustion engine may be, in which the valve unit is additionally equipped with a valve which comprises a valve body which is connected to the flap and in this way mechanically coupled, wherein a pivoting of the flap causes an adjustment of the valve in space and the valve body either releases or obstructs the return line. Consequently, the flap can serve as an actuator for the valve.

All variants of the above embodiment has in common that the flap is used only for adjusting the amount of air supplied via the intake system and not the dosage of the recirculated exhaust gas amount. The latter is accomplished with the valve, which is stuck in the return line when blocking and serves as an EGR valve.

Advantageous embodiments of the supercharged internal combustion engine, in which the node is formed and arranged in the vicinity of the at least one impeller to form a distance .DELTA. A compressor near arrangement of the node shortens the distance of the hot recirculated exhaust gas from the point of introduction into the intake system to the at least one impeller, so that the time in which condensate droplets can form in the free charge air flow is reduced. A formation of condensate droplets is thus counteracted.

In addition, a swirl introduced into the flow using the flap is still effective upon entry of the charge air into the impeller, d. H. still pronounced. Namely advantageous embodiments in which the flap is not flat and at least on the front has at least one deformation as unevenness. The deformation of the flap causes fluidically favorable effects. A substantially axial charge air flow or fresh air flow can with the help of the flap a speed component transverse to the shaft of the compressor, d. H. a twist, to be forced. As a result, the surge limit of the compressor can be shifted towards smaller charge air flows, which is why higher charge pressure ratios are achieved even with small charge air flows.

In this context, embodiments in which the following applies for the distance Δ are advantageous: Δ ≦ 2.0D _V and Δ ≦ 1.5D _V , where D _V indicates the diameter of the at least one impeller. According to advantageous embodiments, which applies to the distance Δ: Δ ≤ 1.0D _V, preferably 0.75D Δ ≤ _V.

In the following the invention with reference to an embodiment and according to 1 described in more detail. Hereby shows:

1 schematically and in a side view arranged in the intake compressor of a first embodiment of the internal combustion engine together with exhaust gas recirculation and valve unit, partially cut.

1 shows schematically and in a side view of the intake system 1 arranged compressor 2 a first embodiment of the internal combustion engine together with exhaust gas recirculation 5 and valve unit 3 , partially cut.

For supplying the charge air to the cylinders, the internal combustion engine has an intake system 1 and for the purpose of charging the cylinders, there is provided an exhaust gas turbocharger having a turbine (not shown) disposed in the exhaust gas discharge system and one in the intake system 1 arranged compressor 2 includes. The compressor 2 is a centrifugal compressor 2 B in its case 2c one on a rotatable shaft 2d stored impeller 2e circulates. The wave 2d of the impeller 2e lies in the plane of the 1 and runs horizontally.

The compressor 2 the exhaust gas turbocharger has an inlet area 2a on, coaxial with the shaft 2d of the compressor 2 runs and is formed so that the section of the intake system 1 upstream of the compressor 2 has no direction changes and the flow of charge air to the compressor 2 the exhaust gas turbocharger or its impeller 2e essentially axially.

The internal combustion engine is further equipped with exhaust gas recirculation 5 equipped, which is a return line 5a which branches off the exhaust gas removal system downstream of the turbine and upstream of the compressor 2 and the compressor impeller 2e forming a node 5b into the intake system 1 empties. The node 5b is present to form a small distance near the compressor 2 arranged.

At the junction 5b is a valve unit 3 arranged, which is a valve body 3d and one in the valve housing 3d arranged flap 3a includes.

To set the amount of recirculated exhaust gas is an EGR valve 6 , which also in the valve body 3d is placed. The EGR valve 6 includes a valve body 6a who is the return line 5a covering in the position shown and with the pivoting flap 3a connected and in this way mechanically with the flap 3a coupled, wherein pivoting the flap 3a an adjustment of the valve body 6a conditionally, ie moving or turning the valve body 6a in the room. Consequently, the flap serves 3a as actuator for the valve 6 or the valve body 6a ,

The flap 3a is an axis transverse to the fresh air flow axis 3b pivotable. This transverse to the fresh air flow axis 3b to which the flap 3a is pivotable, is perpendicular to the plane of the drawing. The present is this axis 3b near a brim of the flap 3a and near a wall portion of the intake system 1 arranged, leaving the flap 3a similar to a door is mounted laterally.

1 shows the flap 3a in two different pivot positions. In a first end position in which the flap 3a perpendicular to the virtual extension of the compressor shaft 2d stands, locks the door 3a with her front 3a' the intake system 1 , In a second end position, in which the flap 3a parallel to the virtual extension of the compressor shaft 2d extends, covering the back 3a'' the flap 3a the return line 5a the exhaust gas recirculation 5 whereas the intake system 1 is released. The valve 6 as such is only for the flap located in the second end position 3a shown.

A pivoting of the flap 3a is with an adjustment of the valve body 6a of the EGR valve 6 connected, with the flap 3a just setting the via intake system 1 supplied amount of air is used and not the dosage of the recirculated exhaust gas amount. The latter is served by the EGR valve 6 ,

The valve housing 3d is on the outside partially with a thermal insulation 4 provided to a cooling of the valve housing 3d located to counteract exhaust gas and thereby the formation of condensation in the valve housing 3d to reduce or prevent. The heat conduction via valve housing 3d to the outside should be inhibited.

LIST OF REFERENCE NUMBERS

1

 intake system

2

 Compressor, compressor of the turbocharger

2a

 Entry area of the compressor of the exhaust gas turbocharger

2 B

 centrifugal compressors

2c

 Housing of the compressor

2d

 Shaft of the compressor

2e

 Impeller of the compressor

3

 valve unit

3a

 flap

3a'

 Front of the flap

3a''

 Rear of the flap

3b

 Swivel axis of the flap

3c

 Storage of the flap

3d

 valve housing

4

 thermal insulation

5

 Exhaust gas recirculation

5a

 Return line

5b

 junction

6

 AGR valve

6a

 valve body

Δ

 Distance of the node to the impeller

AGR

 Exhaust gas recirculation

D _V

 Diameter of the at least one impeller

m _AGR

 Mass of recirculated exhaust gas

_{Fresh air}

 Mass of fresh air supplied

x _AGR

 Exhaust gas recirculation rate

Claims (20)

Charged internal combustion engine with - an intake system ( 1 for supplying a charge air flow, an exhaust gas discharge system for removing exhaust gas, - at least one in the intake system ( 1 ) arranged compressors ( 2 ) with at least one in a housing ( 2c ) on a rotatable shaft ( 2d ) mounted impeller ( 2e ), - exhaust gas recirculation ( 5 ) comprising a return line ( 5a ), which branches off from the exhaust gas removal system and upstream of the at least one impeller ( 2e ) forming a node ( 5b ) into the intake system ( 1 ), and - one at the junction ( 5b ) in the intake system ( 1 ) arranged valve unit ( 3 ), which is a valve housing ( 3d ) and one in the valve housing ( 3d ) arranged flap ( 3a ), wherein the flap ( 3a ) about an axis extending transversely to the fresh air flow ( 3b ) is pivotable in the way that the flap ( 3a ) in a first end position with a front side ( 3a' ) the intake system ( 1 ) and the return line ( 5a ) and in a second end position with a rear side ( 3a'' ) the return line ( 5a ) and the intake system ( 1 ), characterized in that - the valve housing ( 3d ) at least partially with a thermal insulation ( 4 ) is provided. Supercharged internal combustion engine according to claim 1, characterized in that the axle ( 3b ) near an edge portion of the flap ( 3a ) is arranged. Supercharged internal combustion engine according to claim 1 or 2, characterized in that the axis ( 3b ) near a wall section of the intake system ( 1 ) is arranged. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the valve housing ( 3d ) to more than 60% with a thermal insulation ( 4 ) is provided. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the valve housing ( 3d ) to more than 80% with a thermal insulation ( 4 ) is provided. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the valve housing ( 3d ) completely with a thermal insulation ( 4 ) is provided. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) Plastic. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) Ceramic. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) is formed at least by means of surface treatment. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) at least by using different materials for the valve housing ( 3d ) is formed, in the way that one material has a thermal conductivity λ _low and another material has a thermal conductivity λ _high , where: λ _low <λ _high . Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) comprises at least one gas cushion located in a cavity. Supercharged internal combustion engine according to claim 11, characterized in that the at least one cavity is formed at least also by using shuttering elements, wherein the shuttering elements of the formation of an at least partially double-walled valve housing ( 3a ) and thus serve to form the at least one cavity. Supercharged internal combustion engine according to claim 11 or 12, characterized in that the valve housing ( 3a ) is at least partially double-walled, whereby the at least one cavity is formed at least with. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) an exhaust gas loaded inside of the valve housing ( 3a ) at least with forms. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the thermal insulation ( 4 ) an outside of the valve housing which is not exposed to exhaust gas (US Pat. 3a ) at least with forms. Supercharged internal combustion engine according to one of the preceding claims, characterized in that at least one exhaust-gas turbocharger is provided which has a turbine arranged in the exhaust-gas removal system and one in the intake system ( 1 ) arranged compressors ( 2 ). Supercharged internal combustion engine according to claim 16, characterized in that the at least one compressor ( 2 ) of the compressor ( 2 ) of the at least one exhaust gas turbocharger. Supercharged internal combustion engine according to claim 16 or 17, characterized in that the return line ( 5a ) downstream of the turbine the at least one exhaust gas turbocharger branches off from the exhaust gas removal system. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the valve unit ( 3 ) additionally with a valve ( 6 ) equipped with a valve body ( 6a ), which with the flap ( 3a ) and is mechanically coupled in this way, wherein a pivoting of the flap ( 3a ) an adjustment of the valve ( 6 ) and the valve body ( 6a ) the return line ( 5a ) either free or blocked. Supercharged internal combustion engine according to one of the preceding claims, characterized in that the node ( 5b ) in the vicinity of the at least one impeller ( 2e ) is formed and arranged to form a distance Δ.

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