DE102012009288A1 - Internal combustion engine for passenger car, has electrically operated compressor and exhaust gas turbocharger which is provided with various shaped turbines - Google Patents

Abstract

The engine (10) has a main portion that is provided with an exhaust gas turbocharger and an electrically operated compressor (32). The exhaust gas turbocharger is provided with various shaped turbines. The compressor is connected to a voltage source with an electrical voltage range between 10V to 15V. The compressor is connected to absorbent glass mat (AGM) battery as voltage source. An independent claim is included for a method for operating internal combustion engine.

Description

The invention relates to an internal combustion engine having an exhaust gas turbocharger and an electrically operated compressor and a method for operating such an internal combustion engine.

To increase the performance of internal combustion engines charging systems can be used, which provide an increase in pressure in the intake of the engine for increased filling of the combustion chambers with charge air. Often, so-called exhaust gas turbochargers are used, which consist of a turbine and a compressor connected thereto via a shaft. The turbine is integrated into the exhaust system of the internal combustion engine and is thus flowed through by the exiting an internal combustion engine of the internal combustion engine exhaust gas, which is relaxed and transmits part of its flow energy to the turbine. This leads to a rotational movement of a rotor of the turbine, which is transmitted via a shaft to the compressor. The compressor is integrated in the charge air system of the internal combustion engine and ensures compression of the internal combustion engine of the engine supplied charge air.

A principal disadvantage of exhaust gas turbochargers is that they require a sufficiently large exhaust gas mass flow for their function, without no relevant compression performance and thus not the desired increase in performance of the internal combustion engine can be achieved. If, for example, a high load is suddenly requested from an operating point of the internal combustion engine in which it is operated with a low load and thus also with a low exhaust gas mass flow, then some work cycles pass before the larger exhaust gas flow generated by the increased load has accelerated the exhaust gas turbocharger and thereby provides the desired compaction performance. This delay in power delivery is often referred to as a "turbo lag".

To keep this turbo lag sufficiently small, d. H. To achieve a good response of the internal combustion engine, the turbines of exhaust gas turbochargers. which have a fixed turbine geometry, therefore regularly designed so that they produce a relatively high compressor power even at a low exhaust gas mass flow. However, this requires a geometry of the turbine blades that causes a relatively high throttle effect. Although this relatively high throttle effect allows the high performance of the turbine, but at the same time prevents a sufficiently high flow rate of the exhaust gas, if at high speeds and loads of the internal combustion engine, a large exhaust gas mass flow is generated. As a result, the exhaust gas counterpressure increases, which adversely affects the combustion processes in the internal combustion engine. As a rule, exhaust gas turbochargers with fixed turbine geometry are therefore provided with a bypass (a so-called "wastegate"), via which part of the exhaust gas mass flow can be conducted in order to ensure a sufficiently high throughput.

To avoid the formation of a turbo lag as possible, exhaust gas turbochargers have been developed in which the turbine blades upstream vanes are made adjustable. Such turbochargers are also referred to as VTG turbochargers (VTG: Variable Turbine Geometry). In these, the guide vanes can be adjusted with respect to the angle at which the exhaust gas flows against the turbine blades, wherein at a comparatively large angle of attack, the throttle effect, ie. H. the pressure drop across the turbine is relatively large. Then, even with a relatively small exhaust gas mass flow, a relatively high compressor performance can be achieved. With an increasing exhaust gas mass flow then the vanes are adjusted in the direction of a small angle of attack, whereby both a sufficiently high compressor power and a sufficiently high flow rate of the exhaust gas can be ensured by the turbine. In principle, the use of a bypass can be dispensed with.

At present, VTG exhaust gas turbochargers are used almost exclusively in diesel engines. Use in gasoline engines is provided only in individual cases, which is due in particular to the high temperatures of the exhaust gas generated by gasoline engines, which make a considerable constructive and material-technical effort required to make the adjustment of the VTG exhaust gas turbocharger sufficiently temperature resistant. However, the use of VTG exhaust gas turbochargers in gasoline engines promises great potential.

There are two options when using VTG technology: Firstly, the "low-end torque" (LET), d. H. the response at low speeds and loads of the engine compared to a turbocharger with fixed turbine geometry to improve significantly or on the other - for the purpose of significant performance increase over such an exhaust gas turbocharger - to use a larger (VTG) exhaust gas turbocharger, the engine thanks to the VTG technology has a comparable LET. Especially in the first case, very high charging levels can be achieved even at low speeds. For such applications, VTG exhaust gas turbochargers, which additionally have a wastegate, are particularly suitable because they can be well optimized for the lower engine speed range.

The major advantages in stationary operation of the VTG turbocharger on a gasoline engine are mainly due to the very favorable pressure gradient across the cylinder head, the so-called scavenging gradient; due. Due to the variability of the geometry of the turbine high charge pressures can be realized with low back pressures in front of the turbine. As a result, a very good Restgasausspülung is supported in the entire charged operating range of the internal combustion engine, resulting in the consequence of very favorable combustion parameters. However, these advantages in steady-state operation turn into their opposite in dynamic (transient) operation. Since a VTG exhaust gas turbocharger usually always designed slightly larger than an exhaust gas turbocharger with fixed turbine geometry (to realize the advantages described above), should be provided relatively large in transient, ie transient or dynamic operation, the angle of attack of the turbine blades. The thus generated, responsible for the good response high turbine pressure ratio, however, has a negative effect on the scavenging gradient. The purging gradient in transient operation is therefore generally much worse than in stationary operation due to the system. As a result, the Restgasausspülung the combustion chambers is deteriorated, resulting in a delayed response, which is also subjectively often perceived as inharmonious.

As an alternative to using a VTG exhaust gas turbocharger, it has also been proposed to combine an exhaust turbocharger with fixed turbine geometry with an additional compressor which is not driven by the exhaust gas flow of the internal combustion engine. This may be, for example, a mechanically driven compressor (compressor) or even an electrically driven compressor, a so-called e-booster act. The main advantage of an e-booster lies in the ability to drive this regardless of the operating condition of the internal combustion engine. It can thus be provided to operate the e-booster with relatively high power in an operating state of the internal combustion engine in which it is operated with relatively low load and thus with a low exhaust gas flow. The e-booster can then compensate for the existing due to the small exhaust gas mass flow power deficit of the exhaust gas turbocharger. A corresponding internal combustion engine is for example from the DE 101 59 801 A1 known.

Such, an exhaust gas turbocharger and an e-booster combining internal combustion engines have so far found no input into the mass production of motor vehicles. This is due in particular to the fact that the e-booster must be designed to be very powerful in order to be meaningfully combined with the exhaust gas turbocharger. For this purpose, it is particularly necessary that this must provide a sufficiently high compressor performance within a very short period of time and this compressor performance is also required relatively frequently and over a relatively long period.

The integration of such powerful e-Boosters in existing in passenger cars, powered by a voltage of 12 volts electrical system is not possible or only at a disproportionate expense, for example, using a particularly powerful battery: The requested by an e-booster Electrical power, typically greater than 2 kW, is very high for a conventional 12 V electrical system. The occurring currents exceed partially, in particular temporarily significantly 150 A, so that a voltage dip occurs in the electrical system. Voltage dips, however, must be avoided at all costs since, among other things, safety-related components such as an electric power steering system may be affected. In order to prevent an inadmissible voltage dip, for example, an additional capacitor (for example, an Ultracap) or a high-quality battery (for example, a lithium-ion battery or a nickel-metal hydride battery) including disconnectors can be integrated into the electrical system. However, these technologies are on the one hand relatively expensive and on the other hand difficult to integrate in the existing space of the front of a conventional passenger car.

Based on this prior art, the present invention seeks to provide an internal combustion engine with an electrically operated compressor and / or a method for operating such an internal combustion engine, wherein the compressor with a voltage source in an electrical system without complementary, by a circuit breaker electrically separable capacitive components is operable.

This object is solved by the subject matters of the independent claims. Advantageous embodiments of the internal combustion engine according to the invention and the method according to the invention are the subject of the respective dependent claims and will become apparent from the following description of the invention.

Surprisingly, it has been found that the combination of an exhaust gas turbocharger with a variable turbine geometry with an electrically operated compressor, a so-called e-booster, an internal combustion engine can be provided which has a very harmonious transient behavior, at the same time the electric compressor only so rarely for Use must come, that without substantial expenditure also a use in motor vehicles with the currently installed standard electrical system, in particular with an electrical voltage of 12 volts, can be done.

An internal combustion engine according to the invention accordingly has an exhaust gas turbocharger and an electrically operated compressor and is characterized in that the exhaust gas turbocharger is designed with a variable turbine geometry.

In particular, the internal combustion engine may have an internal combustion engine with at least one cylinder, in which a piston is movably guided in the longitudinal axial direction. A mixture of a fuel and charge air (i.e., an oxygen-containing gas, typically air) is burned in a combustion chamber of the cylinder and supplied to an exhaust system. In this exhaust system, a turbine of the exhaust gas turbocharger can be integrated. The turbine is driven in rotation by the exhaust gas flowing through it. The rotational movement of the turbine is transferred to a compressor of the exhaust gas turbocharger, which may be integrated into a charge air system of the internal combustion engine. In the charge air system according to the invention, an electrically operated compressor is additionally integrated. The charge air is compressed by the compressor of the exhaust gas turbocharger and / or the electric compressor and then fed to the cylinder of the internal combustion engine.

Under an exhaust gas turbocharger with a "variable turbine geometry" (VTG exhaust gas turbocharger) is understood according to the invention an exhaust gas turbocharger, the turbine pressure ratio - regardless of a change in the exhaust gas mass flow - by a defined change in the flow geometry is variable. Such an exhaust-gas turbocharger may preferably have at least one turbine with adjustable guide vanes, wherein the angle of inflow, under which the individual guide vanes are impinged by the exhaust gas, is adjustable.

The method according to the invention for operating an internal combustion engine according to the invention is characterized in that the compressor is switched on exclusively in transient operation (and in particular in the case of a sudden load request from an operating state of the internal combustion engine characterized by a low load requirement) and preferably switched off again immediately and, more preferably, Is bypassed (by, for example, a bypass), as soon as the exhaust gas turbocharger even a sufficient Spülgefällte can be achieved. In this case, a good transient response is achieved in an advantageous manner.

A "purging gradient" is understood to mean the ratio of the pressure of the charge air and the exhaust gas pressure upstream of the turbine of the exhaust gas turbocharger. This purging gradient significantly influences the residual gas purging of the cylinder (s) of the internal combustion engine and thus the transient behavior of the internal combustion engine. As a "sufficiently high", a purging gradient can be considered that allows a residual gas purging, in which no more than 10% and preferably not more than 5% residual gas remains in the cylinders.

The combination of a VTG exhaust gas turbocharger with an electric compressor also allows - as is known from the prior art for VTG turbocharger - at an additional load request from a characterized by a low load operating point of the internal combustion engine, the turbine of the exhaust gas turbocharger in the direction of a high Turbine pressure ratio to adjust without the otherwise, d. H. in a VTG exhaust gas turbocharger without support according to the invention by an electric compressor, associated disadvantages and in particular the poor residual gas purging and the concomitant, perceived as inharmonious transient behavior of the internal combustion engine to accept. Rather, a poor Restgasausspülung is prevented by the electric compressor and the pressure increase generated by this on the charge air side of the internal combustion engine. On the other hand, as soon as the VTG turbocharger itself can again ensure a favorable flushing gradient, the electric compressor can be switched off and then preferably bypassed by a bypass. As a result, this very low turn-on of the electric compressor can be achieved, whereby this can be integrated with relatively little effort in motor vehicles with an electrical 12 V electrical system.

In a preferred embodiment of the internal combustion engine according to the invention is therefore also provided to connect the compressor to a voltage source with an electrical voltage of 10 V to 15 V and in particular 12 V to 14 V and more preferably of about 12 V. In particular, the compressor can be connected to a voltage source in a vehicle electrical system without additional without complementary, can be electrically separated by a circuit breaker capacitive components.

The voltage source may preferably be a lead-acid battery, in particular a conventional wet lead-acid battery. The lead-acid battery preferably has a capacity of greater than or equal to 20 Ah.

However, the e-booster operation also increases the energy throughput through the battery. In order to ensure the life of the battery despite the increased energy throughput, it is particularly preferred to use a special design of the lead-acid battery: an Absorbent-glass-Mat battery (AGM battery). Such batteries are installed, for example, in passenger cars with start-stop systems.

Furthermore, the internal combustion engine according to the invention may have a bypass bypassing the compressor. This bypass is preferably switchable, d. H. the proportion of the charge air conducted via the bypass can be regulated, preferably between 0% and 100%.

Regardless of the possibility of realizing the internal combustion engine according to the invention in a motor vehicle with a 12 V electrical system, the advantages of the internal combustion engine according to the invention also in such vehicles, the higher vehicle electrical system voltage (for example, hybrid vehicles, ie, an internal combustion engine and an electric traction drive combining vehicles) exhibit, be exploited. The higher the on-board voltage, the stronger the support of the electric compressor can in principle be configured, as a result of which in turn the VTG turbocharger can be made larger. As a result, the performance increase of the internal combustion engine achieved by the exhaust-gas turbocharger can be further increased. For example, in an internal combustion engine according to the invention, which is integrated with an electrical system having a relatively small capacity, an electric compressor can be combined with a VTG exhaust gas turbocharger, wherein the VTG exhaust gas turbocharger additionally has a wastegate. When combined with a higher capacity electrical system, on the other hand, a more powerful electric compressor can be combined with a VTG turbocharger without wastegate.

Preferably, the inventive combination of a VTG exhaust gas turbocharger with an electric compressor is provided in an internal combustion engine, which is operated according to the Otto principle.

The invention will be explained in more detail with reference to an embodiment shown in the drawing. In the drawing shows:

1 : an internal combustion engine according to the invention in a schematic representation.

The 1 shows a schematic representation of an embodiment of an internal combustion engine according to the invention. The internal combustion engine comprises a four-cylinder internal combustion engine 10 , In the four cylinders 12 of the internal combustion engine 10 a mixture of fuel and air is burned. The resulting exhaust gases are via a turbine 14 passed an exhaust gas turbocharger integrated in an exhaust line of the internal combustion engine, where they are relaxed, with energy to a rotor of the turbine 14 is transmitted to drive this rotating. The turbine 14 of the exhaust gas turbocharger is provided with a variable turbine geometry, so that by an actuator, which is preferably not electrically operated (alternatively, for example, pneumatic), can be carried out an adjustment of vanes of the turbine to the turbine pressure ratio, ie the ratio of the exhaust pressure before and behind the turbine to actively influence. Furthermore, there is a wastegate 16 , ie a turbine bypassing (first) bypass provided. Via an electrically controllable valve 18 can the flow rate of exhaust gas through the wastegate 16 be regulated in any values between 0% and 100%. After the exhaust the turbine 14 the exhaust gas turbocharger or the wastegate 16 has passed through, this is supplied to an exhaust system of the exhaust system, of the in the 1 only a precatalyst 20 is shown. The exhaust gas is then blown into the atmosphere via the exhaust system.

The rotor of the turbine 14 the exhaust gas turbocharger is over a shaft 22 with an impeller of a compressor 24 the exhaust gas turbocharger connected. About this compressor 24 is from the internal combustion engine 10 sucked air (charge air) pre-compressed, resulting in a higher filling of the cylinder 12 and as a result, a power increase of the internal combustion engine 10 should be achieved. Optionally, it can also be provided, including the compressor 24 the exhaust gas turbocharger with a (second) bypass 26 to provide, with the proportion of the over the bypass 26 guided air through a valve 28 is controllable.

Depending on the respective operating point of the internal combustion engine 10 , ie in particular the speed of the internal combustion engine 10 as well as the amount of each working cycle in the four cylinders 12 introduced fuel (ie the load), that of the compressor 24 the exhaust gas turbocharger compressed charge air either via an electrically from a controllable electric motor 30 driven compressor 32 or a (third) bypass 34 in which a control flap 36 (ie a valve) is integrated, guided. It is provided, the charge air only via the electric compressor 32 to lead (and to drive this electrically) when from an operating condition of the internal combustion engine 10 with low load out an increased load request. In particular, the actual pressure in one behind the electric compressor can / can be used as controlled variables 32 or the bypass 34 arranged suction pipe, a defined, specific for the respective operating point target pressure in the intake manifold and / or alternative, the load request of the internal combustion engine 10 descriptive quantities, the actual pressure after the compressor 24 the exhaust gas turbocharger and / or after the electric compressor 32 , the actual pressure in front of the turbine 14 the exhaust gas turbocharger and / or suitable values for detecting a transient operating state of the internal combustion engine 10 , z. B. a Farbpedalgradient and / or the difference between the actual and nominal load of the engine are used. Here, one, several or all of these values can be used. The values can either be measured by suitable sensors or calculated (ie modeled) by suitable models.

Due to the support of the turbocharger, due to the initially low load, with the internal combustion engine 10 is operated, only a correspondingly low compressor power provides, by means of the electric compressor 32 can an improved residual gas purging and as a result of a more harmonious transient behavior of the internal combustion engine 10 be achieved.

As soon as the exhaust gas turbocharger ensures sufficient residual gas purging due to the increased exhaust gas mass flow due to the increased load requirement, the electric compressor becomes 32 switched off again and the charge air via the bypass 34 led to a pressure drop across the (switched off) electric compressor 32 to avoid.

The over the electric compressor 32 or the (third) bypass 34 guided charge air is then via a built-in intake manifold of the internal combustion engine throttle 38 and a charge air cooler 40 the individual cylinders 12 of the internal combustion engine 10 fed. The intercooler 40 is liquid cooled, with the cooling liquid from a pump 42 in a circuit between the intercooler 40 as well as a cooler 44 is conveyed for the cooling liquid. The intercooler may alternatively be air cooled.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10159801 A1 [0009]

Claims (10)

Internal combustion engine with an exhaust gas turbocharger and an electrically operated compressor ( 32 ), characterized in that the exhaust gas turbocharger is formed with a variable turbine geometry. Internal combustion engine according to claim 1, characterized in that the compressor ( 32 ) is connected to a voltage source with a voltage of 10 V to 15 V. Internal combustion engine according to claim 2, characterized in that the voltage source has a voltage of 12 V to 14 V. Internal combustion engine according to one of the preceding claims, characterized in that the electrically operated compressor is connected to a lead-acid battery as a voltage source. Internal combustion engine according to claim 4, characterized in that the lead-acid battery is an Absorbent Glass Mat battery Internal combustion engine according to one of the preceding claims, characterized in that it is designed for operation according to the Otto principle. Internal combustion engine according to one of the preceding claims, characterized by a compressor ( 32 ) immediate bypass ( 36 ). Method for operating an internal combustion engine according to one of the preceding claims, characterized in that the compressor ( 32 ) is switched on only in transient operation and preferably at an increased load request from a characterized by a low load operating condition out. A method according to claim 8, characterized in that the exhaust gas turbocharger during operation of the compressor ( 32 ) is adjusted in the direction of a high turbine pressure ratio. Method according to claim 8 or 9, characterized in that the compressor ( 32 ) is switched off again as soon as a sufficiently high scavenging gradient can be provided by the exhaust gas turbocharger.

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