DE202013104782U1 - Internal combustion engine with cooling - Google Patents

Abstract

Internal combustion engine with at least one cylinder head (1), which has at least two cylinders (2), in which
- Each cylinder (2) at least one outlet opening (4b) for discharging the exhaust gases via Abgasabführsystem (4), wherein each exhaust port (4b) is followed by an exhaust pipe (4a),
- Each cylinder (2) has at least one inlet opening (3b) for supplying air via the intake system (3), and
- The exhaust pipes (4a) of at least two cylinders (2) merge to form an exhaust manifold at a collection point of Abgasabführsystems (4) to an overall exhaust line,
characterized in that
- Is provided upstream of the collection point at least one opening (5) in Abgasabführsystem (4) to which a compressed air supply line (6) upstream and which serves the introduction of air into the Abgasabführsystem (4) for the purpose of cooling the at least one cylinder head (1) ,

Description

• – jeder Zylinder mindestens eine Auslassöffnung zum Abführen der Abgase via Abgasabführsystem aufweist, wobei sich an jede Auslassöffnung eine Abgasleitung anschließt,
• – jeder Zylinder mindestens eine Einlassöffnung zum Zuführen von Luft via Ansaugsystem aufweist, und
• – die Abgasleitungen von mindestens zwei Zylindern unter Ausbildung eines Abgaskrümmers an einer Sammelstelle des Abgasabführsystems zu einer Gesamtabgasleitung zusammenführen.

The invention relates to an internal combustion engine having at least one cylinder head, which has at least two cylinders, in which

• Each cylinder has at least one outlet opening for discharging the exhaust gases via the exhaust gas removal system, wherein an exhaust gas line adjoins each outlet opening,
• - Each cylinder has at least one inlet opening for supplying air via the intake system, and
• - Combine the exhaust pipes of at least two cylinders to form an exhaust manifold at a collection point of Abgasabführsystems to an overall exhaust line.

Internal combustion engines of the type mentioned are used as a drive for motor vehicles. In the context of the present invention, the term internal combustion engine comprises gasoline engines and diesel engines, but also hybrid internal combustion engines that use a hybrid combustion process, as well as hybrid propulsion systems which, in addition to the internal combustion engine, comprise an electric machine which can be electrically connected to the internal combustion engine and which receives power from the internal combustion engine or as switchable auxiliary drive additionally delivers power.

Internal combustion engines have at least one cylinder head, which is used to form the at least two cylinders, d. H. Combustion chambers, connected to a cylinder block. As part of the charge exchange, the exhaust of the combustion gases via the outlet openings and the filling of the combustion chamber, d. H. suction of air, through inlet ports of at least two cylinders. To control the charge cycle four-stroke engines almost exclusively lift valves are used as control members that perform an oscillating stroke during operation of the internal combustion engine and thus release the inlet and outlet ports and close. The required for the movement of the valves valve actuating mechanism including the valves themselves is referred to as a valve train.

The cylinder head is used to hold the controls and overhead camshaft to accommodate the entire valve train. In spark-ignited internal combustion engines, moreover, the required ignition device, in direct-injection internal combustion engines beyond the injection device can be arranged in the cylinder head. To form a functional, d. H. the combustion chambers sealing connection of cylinder head and cylinder block are to provide sufficient and sufficiently large holes, which significantly affects the structural design of the cylinder head. If the internal combustion engine has liquid cooling, at least one coolant jacket is integrated in the at least one cylinder head, which passes the coolant through the cylinder head.

The above statements make it clear that the at least one cylinder head of an internal combustion engine is a thermally and mechanically highly loaded component. The demands on the cylinder head continue to increase. It should be noted in this context that an increasing proportion of internal combustion engines - by turbocharger supercharger or mechanical supercharger - is charged. Due to the increasingly dense packaging in the engine compartment and the increasing integration of components and components in the cylinder head, for example, the integration of the exhaust manifold, in particular increases the thermal load of the internal combustion engine or the cylinder head, so that increased cooling requirements and measures to are seize that prevent a thermal overload of the internal combustion engine safely.

In principle, it is possible to carry out the engine cooling in the form of air cooling or liquid cooling. In the air cooling, the internal combustion engine is provided with a fan, wherein the heat dissipation takes place by means of a guided over the surface of the cylinder head air flow.

Due to the higher heat capacity of liquids compared to air can be dissipated with a liquid cooling much larger amounts of heat than is possible with an air cooling. For this reason, internal combustion engines are increasingly equipped with a liquid cooling.

Liquid cooling requires the equipment of the internal combustion engine or of the at least one cylinder head with at least one coolant jacket, d. H. the arrangement of the coolant through the cylinder head leading coolant channels. The heat given off to the coolant is withdrawn from the coolant in a heat exchanger, which is preferably arranged in the front-end region of the vehicle.

In general, the design of the engine cooling takes place, regardless of whether it is designed as air cooling or liquid cooling, with regard to the maximum occurring cooling demand. The result of this approach is engine cooling which, with respect to normal driving, i. H. is oversized in view of the average cooling demand.

In order to reliably prevent the overheating of the engine, the cooling performance of the engine cooling is designed for operating conditions with very high or maximum cooling demand, which are characterized by high loads at the same time low vehicle speeds, ie in terms of operating conditions such as those occur during acceleration and uphills in order to deliver the requested cooling capacity even under the most adverse conditions. Under such conditions, the engine cooling has to cope with a very large amount of heat, ie dissipate, without the required for the heat dissipation air flow is available.

The design of the engine cooling with respect to the scenario described above leads to disproportionately large, d. H. oversized cooling. As a result, the fan of air cooling or the heat exchanger, d. H. the cooler of a liquid cooling, very large dimensions and that, although this is not necessary for normal driving, d. H. apart from a few extreme driving situations would actually be unnecessary.

In particular, such a design results in a liquid cooling to an excessively large cooler, which is difficult to accommodate in the front-end area of a vehicle.

To take into account in this context, in particular, that the radiator can not be increased arbitrarily, since usually more heat exchangers, in particular cooling devices, must be provided in order to ensure safe, trouble-free operation of the internal combustion engine and to optimize the operation of the internal combustion engine, and an oversized cooler greatly limits the other heat exchangers in arrangement and dimensioning.

In the following some examples for further heat exchangers are called and described, in order to clarify the problem.

The heat released as a result of the combustion of the fuel is not only delivered to the walls delimiting the combustion chamber, the exhaust gas flow and optionally to the engine coolant, but also partially to the engine oil. In order to comply with the maximum permissible oil temperature, the heat dissipation via the oil pan due to heat conduction and natural convection is often not sufficient, so that an additional oil cooler is provided.

On the intake side of an internal combustion engine, a charge air cooler is often arranged in the intake system, which lowers the temperature of the intake air and thus increases the density of the cylinder fresh charge. In this way, a charge air cooler contributes to a better filling of the combustion chamber with air or with fresh mixture. Usually supercharged internal combustion engines are equipped with a charge air cooler.

In addition to the charge air cooler, internal combustion engines often have further heat exchangers, in particular cooling devices.

Modern internal combustion engines are increasingly being equipped with exhaust gas recirculation (EGR). The exhaust gas recirculation, d. H. the recirculation of combustion gases from the exhaust side to the intake side of the internal combustion engine is considered to be effective in meeting future emissions limits, particularly nitrogen oxide emission limits. Since the formation of nitrogen oxides requires high temperatures, a concept for reducing nitrogen oxide emissions is to develop combustion processes with lower combustion temperatures, with exhaust gas recirculation as a means of reducing temperatures.

With increasing exhaust gas recirculation rate, the nitrogen oxide emissions can be significantly reduced. In this case, the exhaust gas recirculation rate x _{AGR is} determined as x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _AGR denotes the mass of recirculated exhaust gas and m _{fresh air} the supplied and possibly compressed fresh air or charge air.

In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates are required, which can be on the order of x _AGR ≈ 50% to 70%.

To realize such high recirculation rates, cooling of the recirculated exhaust gas, i. H. a compression of the exhaust gas by cooling, imperative to increase the density of the recirculated exhaust gas. The internal combustion engine is therefore equipped with an additional cooling device for cooling the recirculating exhaust gas.

Other coolers can be provided, for example for cooling the transmission oil in automatic transmissions and / or for cooling hydraulic fluids, in particular hydraulic oil, which is used in the context of hydraulically actuated adjusting devices or for steering assistance.

Another heat exchanger is the air condenser of an air conditioner, which usually works after the cold steam process. The temperature of the passenger compartment supplied air flow is lowered when flowing around an evaporator, the air flow inside the evaporator inside flowing refrigerant extracts the heat and thereby evaporates itself.

The above explanations make it clear that modern internal combustion engines are equipped with a plurality of heat exchangers, which must be formed without exception to fulfill their function with a sufficiently large heat transfer surface, resulting in the dimensioning and arrangement of the individual heat exchangers in the front-end area due to limited space is often problematic, d. H. leads to conflicts.

In the prior art, therefore, coolers are already arranged in series, spaced from each other and partially overlapping. Optionally, flow baffles are used to guide the flow of air through the engine compartment.

In this context, the radiator of the engine cooling is of particular importance, since this cooler is indispensable for safe operation of the internal combustion engine and has to cope with large amounts of heat.

To the heat exchangers of the cooling systems, d. H. the cooling devices, even at a standstill, d. H. provide a sufficiently high air mass flow when the vehicle is stationary, or at low vehicle speeds, some cooling systems modern motor vehicle drives are equipped with powerful fan motors that drive a fan, d. H. set in rotation. The fan motors are usually operated electrically and can support the heat transfer in the heat exchangers in principle at any operating point. The control of such fan motors by means of motor control.

Nevertheless, further measures are required to limit the thermal load of an internal combustion engine even under the most adverse conditions.

In order to avoid a thermal overload of individual components of the internal combustion engine, enrichment (λ <1) is frequently always carried out according to the prior art whenever high exhaust gas temperatures are to be expected. In this case, more fuel is injected than can be burned at all with the amount of air provided, wherein the excess fuel is also heated and evaporated, so that the temperature of the combustion gases decreases. However, this procedure is considered to be disadvantageous from an energetic point of view, in particular with regard to the fuel consumption of the internal combustion engine, and with regard to the pollutant emissions.

The exhaust gas temperatures can in principle also be reduced by leaning (λ> 1) of the fuel-air mixture. The effect is similar to an enrichment. While too much fuel is injected during enrichment (λ <1), less fuel is injected in an emptying than could be burned with the amount of air provided, that is to say, in the case of enrichment. H. more air is provided than is needed to burn the fuel, with the excess air participating in the combustion process, i. H. is heated with. As a result, the temperature of the combustion gases also decreases. The reduction in temperature due to emaciation is much lower than when enriched, because the excess air, unlike the excess fuel, does not have to be evaporated.

Against the background of the foregoing, it is the object of the present invention to provide an internal combustion engine according to the preamble of claim 1, which has an improved compared to the prior art cooling.

• – jeder Zylinder mindestens eine Auslassöffnung zum Abführen der Abgase via Abgasabführsystem aufweist, wobei sich an jede Auslassöffnung eine Abgasleitung anschließt,
• – jeder Zylinder mindestens eine Einlassöffnung zum Zuführen von Luft via Ansaugsystem aufweist, und
• – die Abgasleitungen von mindestens zwei Zylindern unter Ausbildung eines Abgaskrümmers an einer Sammelstelle des Abgasabführsystems zu einer Gesamtabgasleitung zusammenführen,

und die dadurch gekennzeichnet ist, dass

• – stromaufwärts der Sammelstelle mindestens eine Öffnung im Abgasabführsystem vorgesehen ist, an die sich stromaufwärts eine Druckluftversorgungsleitung anschließt und die dem Einbringen von Luft in das Abgasabführsystem zwecks Kühlung des mindestens einen Zylinderkopfes dient.

This object is achieved by an internal combustion engine having at least one cylinder head, which has at least two cylinders in which

• Each cylinder has at least one outlet opening for discharging the exhaust gases via the exhaust gas removal system, wherein an exhaust gas line adjoins each outlet opening,
• - Each cylinder has at least one inlet opening for supplying air via the intake system, and
• - merge the exhaust gas lines of at least two cylinders to form an exhaust gas manifold at a collection point of the Abgasabführsystems to an overall exhaust gas line,

and which is characterized in that

• - Is provided upstream of the collection point at least one opening in the Abgasabführsystem, to which upstream of a compressed air supply line connects and which serves to introduce air into the Abgasabführsystem for the purpose of cooling the at least one cylinder head.

According to the invention air is selectively introduced into the Abgasabführsystem to cool the at least one cylinder head and thus the internal combustion engine and reduce the thermal stress of the cylinder head. According to the invention, the air blown into a hot exhaust pipe, due to flow conditions, attaches to the wall delimiting the exhaust pipe, which is at least formed by the cylinder head, and thus forms a film-like insulation which keeps the hot exhaust gases away from the cylinder head material.

The veil cooling according to the invention not only extracts heat from the cylinder head by convection. Rather, the air curtain prevents or impedes the direct introduction of heat from the hot exhaust gas into the cylinder head, whereby the thermal stress of the cylinder head a priori reduced, that is reduced.

The procedure according to the invention is therefore characterized by the fact that the heat input into the cylinder head is reduced or made more difficult by creating a thermal barrier. The reduced heat input into the cylinder head relieves an optionally provided cooling of the internal combustion engine, d. H. the engine cooling. This allows in particular to dimension the radiator of the engine cooling smaller.

On a enrichment at exhaust gas temperatures, which indicate an additional cooling demand according to the prior art, can be dispensed with according to the invention. This leads to a qualitative improvement in the overall cooling, since unnecessary enrichment is omitted, which is extremely advantageous, because under energetic aspects, in particular with regard to the fuel consumption of the internal combustion engine, and in terms of pollutant emissions enrichment is disadvantageous. In particular, enrichment does not always allow the internal combustion engine to be operated as desired or in the manner as would be required, for example, for a proposed exhaust aftertreatment system.

Regardless of what has been stated above, enrichment can also take place in the case of an internal combustion engine according to the invention, i. H. performed, for example, a enrichment for lowering the exhaust gas temperature to protect an exhaust aftertreatment system or a turbine from overheating, but also as an additional cooling measure in extreme driving situations with maximum cooling demand.

With the internal combustion engine according to the invention, the object underlying the invention is achieved, namely an internal combustion engine provided according to the preamble of claim 1, which has an improved compared to the prior art cooling.

Embodiments of the internal combustion engine in which the at least one cylinder head is made of aluminum at least partially, preferably predominantly or completely, are advantageous. This brings in particular weight advantages.

Embodiments of the internal combustion engine in which liquid cooling is provided are advantageous, with at least one coolant jacket, which belongs to a coolant-carrying coolant circuit, in which at least one cylinder head is integrated in order to form the liquid cooling. Due to the high heat capacity of a liquid can be removed with a liquid cooling very large amounts of heat.

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

Embodiments of the internal combustion engine in which the exhaust gas lines of the at least two cylinders within the cylinder head merge to form the overall exhaust gas line are advantageous. The combination of exhaust pipes to an overall exhaust line is generally and in the context of the present invention referred to as exhaust manifold.

When supercharged by exhaust gas turbocharger internal combustion engines, it is basically endeavored to arrange the turbine of an exhaust gas turbocharger as close to the outlet openings of the cylinder to keep the path of the hot exhaust gases turbine wheel as short as possible and the line volume upstream of the turbine wheel small. The most extensive integration of the exhaust pipes or the exhaust manifold in the cylinder head is purposeful.

The length of the exhaust pipes is reduced by integration into the cylinder head. On the one hand thereby the line volume, d. H. reduces the exhaust gas volume of the exhaust pipes upstream of a turbine, so that the response of this turbine is improved. On the other hand, the shortened exhaust pipes also lead to a lower thermal inertia of the exhaust system upstream of the turbine, so that the temperature of the exhaust gases is increased at the turbine inlet, which is why the enthalpy of the exhaust gases at the inlet of the turbine is higher. Optionally provided exhaust aftertreatment systems achieve a required minimum operating temperature faster.

The integration of the exhaust manifold basically leads to a more compact design of the internal combustion engine and allows a tight packaging of the entire drive unit in the engine compartment. In addition, there are cost advantages in the production. A simplification of the assembly and a weight reduction of the internal combustion engine are further advantages. A production of the exhaust manifold made of temperature-resistant material is eliminated because of the inventive air curtain cooling or optionally integrated in the cylinder head liquid cooling can be participated.

Embodiments of the internal combustion engine in which at least one exhaust-gas turbocharger comprising a compressor arranged in the intake system and a turbine arranged in the exhaust-gas removal system are provided are advantageous, the turbine being arranged downstream of the collection point in the exhaust-gas removal system.

An exhaust gas turbocharger comprises a compressor arranged in the intake system and a turbine arranged in the exhaust gas discharge system, which are arranged on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in this 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 charging of the at least two cylinders is achieved. Optionally, a charge air cooling is provided, with which the compressed charge air is cooled before entering the cylinder. It may be advantageous to equip the intercooler with a bypass line in order to bypass the intercooler if necessary, for example after a cold start.

The advantage of the exhaust gas turbocharger, for example compared to a mechanical supercharger, is that no mechanical connection is required for the power transmission between the supercharger and the internal combustion engine. While a mechanical supercharger obtains the energy required for its drive completely from the internal combustion engine and thus reduces the power provided and thus adversely affects the efficiency, the exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases.

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. At the same vehicle boundary conditions, the load collective can thus be shifted to higher loads in which the specific fuel consumption is lower.

Difficulty is often the interpretation of turbocharging turbocharger, with basically a noticeable increase in performance in all speed ranges is sought. In the prior art, a torque drop is often observed when falling below a certain speed. The torque characteristic of a supercharged internal combustion engine can be improved by different measures, for example, the fact that a plurality of superchargers - exhaust gas turbocharger and / or mechanical supercharger - are provided in parallel and / or arranged in series.

In this connection, embodiments of the internal combustion engine in which the compressed air supply line branches off from the intake system downstream of the compressor are advantageous.

In internal combustion engines in which the compressor is equipped with a blow-off line which branches off from the intake system downstream of the compressor, embodiments can also be advantageous, which are characterized in that the compressed-air supply line branches off from the blow-off line.

According to the invention, the air is introduced into the exhaust gas removal system against the exhaust back pressure prevailing in the exhaust gas removal system. Also to be considered is the gas dynamics that occur during the charge cycle in the exhaust gas removal system, together with pre-discharge impacts.

The pressure gradient necessary for the introduction of the air is in this case generated using the compressor of the exhaust gas turbocharger, d. H. anyway, pressurized and available air is already being used. An additional compressor for feeding the compressed air supply line can thus be dispensed with.

Nevertheless, in non-supercharged internal combustion engines, an additional compressor or a different compressed air reservoir for supplying the compressed air supply line can be provided or used.

Embodiments of the internal combustion engine in which at least two mutually spaced openings are provided in at least one exhaust pipe are advantageous.

To form a film-like air curtain serving as insulation or thermal barrier, it is advantageous to provide two or more openings. Several openings facilitate the introduction of the air in such a way that the exhaust pipe delimiting, from the cylinder head with trained wall over a large area, preferably fully wetted with air and is acted upon. Ideally, a trachea or trachea flow surrounding the exhaust gas is formed.

For the reasons mentioned above, embodiments of the internal combustion engine are therefore advantageous in this context, in which the at least two openings along a circumference of the exhaust pipe are arranged spaced from each other.

For the above reasons, embodiments of the internal combustion engine are advantageous in this context, in which at least three openings are arranged in a ring around the exhaust pipe spaced from each other.

Embodiments of the internal combustion engine in which the at least three openings are arranged in a ring-shaped manner around the at least one outlet opening of at least one cylinder are advantageous. Then, the exhaust pipe associated with the at least one exhaust port is opened from the beginning, i. H. starting from the heat source, namely the combustion chamber, cooled or protected by Schleierkühlung from excessive heat input. It should be noted in this context that the thermal stress of the cylinder head increases toward the outlet opening.

In internal combustion engines in which the at least one outlet opening of a cylinder is associated with an outlet valve which is mounted in the closed position in a valve seat and closes the outlet opening, embodiments are advantageous, which are characterized in that the at least three openings are arranged in the region of the valve seat wherein the exhaust valve closes the at least three openings in the closed position. Then, the outlet valve simultaneously acts as a shut-off element, which serves to activate or deactivate the curtain cooling. There are synergy effects, since hot exhaust gases are discharged into the Abgasabführsystem on the one hand with open exhaust valve and on the other hand, the then existing cooling demand is directly satisfied, since the opening of the exhaust valve simultaneously and as needed, the veil cooling is activated.

Advantageous embodiments of the internal combustion engine, in which the compressed air supply line to the at least one opening at the exhaust side end an acute angle α with the respective exhaust pipe forms with α <45 °, preferably with α <25 °. The compressed air supply line in the present case forms with the center axis of the exhaust pipe, d. H. with the central current thread of the exhaust gas flow leading through the exhaust pipe an acute angle α.

A tangential introduction of the air into the exhaust pipe supports the formation of a film-like air curtain on the inner walls of the Abgasabführsystems and thus the formation of insulation or thermal barrier.

Embodiments of the internal combustion engine in which a shut-off element is arranged in the compressed air supply line are advantageous.

In an internal combustion engine with cooling, it is not intended and also not advantageous that the cooling absorbs the largest possible amount of heat under all operating conditions. Rather, basically a demand-based control of the cooling is sought, which takes into account the different operating modes of an internal combustion engine and takes into account that it may be advantageous to extract less heat from the engine, for example in the warm-up phase. Namely, to reduce the fuel consumption, rapid heating of the engine oil in order to reduce the friction power, especially after a cold start, is expedient. A heating of the engine oil causes a decrease in the viscosity of the oil and thus provides for a reduction of the friction or friction, especially in the oil-supplied bearings, such as the bearings of the crankshaft. The engine oil can basically be heated up in an accelerated manner so that as little heat as possible is withdrawn from the internal combustion engine during the warm-up phase, whereby the heating of the internal combustion engine is forced.

For the reasons mentioned above, it is therefore advantageous to arrange a shut-off element in the compressed air supply line. The shut-off element is used to activate or deactivate the veil cooling and thus enables a needs-based cooling.

Different embodiments, however, do not require an additional shut-off element in the compressed air supply line. In supercharged internal combustion engines in which the compressor of an exhaust gas turbocharger is equipped with a Abblaseleitung in which a shut-off element for controlling the blow-off is arranged, the compressed air supply line from the blow-off line downstream of this shut-off branch, so that the compressed air supply line is fed with air, if the blow-off line is or is released by opening the associated shut-off element for the purpose of charge air blow-off.

If the at least one opening is arranged in the region of the valve seat, the associated outlet valve also functions as a shut-off element which connects the compressed-air supply line via the opening to the exhaust-gas removal system and separates it from the exhaust-gas removal system.

Advantageous embodiments of the internal combustion engine, in which the at least one opening as a nozzle, d. H. nozzle-like, is formed.

Embodiments of the internal combustion engine in which the at least one opening in a part of the exhaust-gas removal system are advantageous is provided, which is integrated in the at least one cylinder head.

Embodiments of the internal combustion engine in which the compressed air supply line is at least partially integrated in the at least one cylinder head are advantageous.

Advantageous embodiments of the internal combustion engine, in which the at least one opening is provided in an exhaust pipe of Abgasabführsystems, which is integrated in the at least one cylinder head.

To limit and reduce the thermal load of an internal combustion engine of the aforementioned type, it is advantageous to introduce air upstream of the collection point by means of compressed air supply line via the at least one opening in the Abgasabführsystem the internal combustion engine to cool the at least one cylinder head.

Advantageously, the air is introduced as a function of the load and / or the rotational speed of the internal combustion engine via the at least one opening in the Abgasabführsystem for the purpose of cooling the at least one cylinder head.

• – eine Temperatur T ermittelt wird, und
• – Luft via der mindestens einen Öffnung in das Abgasabführsystem eingebracht wird, falls die Temperatur T eine vorgebbare Grenztemperatur T_Grenz,up übersteigt mit T ≥ T_Grenz,up.

Also advantageous are variants in which

• - A temperature T is determined, and
• - Air is introduced via the at least one opening in the Abgasabführsystem if the temperature T exceeds a predetermined limit temperature T _{limit, up} with T ≥ T _{limit, up} .

The temperature may be a component temperature, an exhaust gas temperature or a coolant temperature. As a basis for decision for the cooling of the cylinder head, the determined temperature is used.

It is advantageous to determine the temperature T mathematically. The mathematical determination of the temperature T takes place, for example, by means of simulation, in which models known from the prior art, for example dynamic heat models and kinetic models, are used to determine the heat of reaction generated during the combustion. As input signals for the simulation operating parameters of the internal combustion engine are preferably used, which are already present, d. H. be determined in a different context.

The simulation calculation is characterized in that no further components, in particular no sensors, have to be provided in order to determine the temperature, which is favorable in terms of cost. The disadvantage, on the other hand, is that the temperature determined in this way is merely an estimated value, which can reduce the quality of the control or regulation of the curtain cooling.

It is therefore also advantageous to measure the temperature T metrologically by means of a sensor directly.

In this case, variants are advantageous in which the internal combustion engine is equipped with a motor control and the temperature T detected by means of a sensor is provided as an input variable.

Whether a temperature T is determined by calculation or measured by means of a sensor also depends on the type of temperature. The metrological detection of an exhaust gas temperature T _exhaust is often difficult, since during operation of the internal combustion engine very high temperatures in the exhaust gas can be achieved. The metrological detection of a cylinder head _temperature T _cyl, however, prepares no difficulties. A cylinder head has comparatively moderate temperatures, even when the internal combustion engine has warmed up, and also offers a multitude of possibilities, ie different locations, for arranging a sensor without impairing the functionality of the internal combustion engine.

• – eine Temperatur T_cyl des mindestens einen Zylinderkopfes ermittelt wird, und
• – Luft via der mindestens einen Öffnung in das Abgasabführsystem eingebracht wird, falls die Zylinderkopftemperatur T_cyl eine vorgebbare obere Grenztemperatur T_Grenz,up übersteigt mit T_cyl ≥ T_Grenz,up.

Advantageous are variants in which

• A temperature T _{cyl of} the at least one cylinder head is determined, and
• - Air is introduced via the at least one opening in the _{Abgasabführsystem} if the cylinder head temperature T _{cyl exceeds} a predetermined upper limit temperature T _{limit, up} with T _cyl ≥ T _{limit, up} .

In the present case, cooling takes place as a function of the cylinder head _temperature T _cyl . This is turned off directly to the engine to be cooled or the cylinder head to be cooled and thus to the component, which is the immediate subject of the method for cooling. Whether a cooling is made or not, is decided on the basis of the currently present temperature of the cylinder head T _cyl .

For estimating the cylinder head _temperature T _cyl, it is also possible to use another component temperature, in particular a cylinder block temperature, which is detected, for example, by measurement using a sensor or determined mathematically by means of a simulation calculation. According to this variant, the temperature of the cylinder head is determined indirectly - using a different temperature.

In a liquid-cooled internal combustion engine, there is also the possibility of the cylinder head _temperature T _cyl using the Temperature of the coolant to determine, ie estimate.

It is advantageous to determine the cylinder head _temperature T _cyl at the location of the head at which a very high or the maximum head temperature is reached or expected.

Also, a cylinder head temperature T _cyl are detected at a location to detect the temperature T _cyl elsewhere in the head, that is estimated, namely for a position to which the predetermined limit temperature refers. This procedure, ie to detect the temperature at one point by measurement and to specify the limit temperature for another site is basically possible, but requires the transformation of the temperature for comparison.

The use of the cylinder head _temperature T _cyl as a decision _criterion for the cooling is characterized by the fact that exactly the temperature is used for controlling or regulating the cooling, which is to be limited or reduced in the context of cooling, namely the cylinder head _temperature T _cyl .

Nevertheless, an exhaust gas temperature could be monitored and determined and used as an indication of a required cooling in order to avoid overheating of the internal combustion engine and to limit the cylinder head _temperature T _cyl .

• – eine Abgastemperatur T_exhaust im Abgasabführsystem ermittelt wird, und
• – Luft via der mindestens einen Öffnung in das Abgasabführsystem eingebracht wird, falls die Abgastemperatur T_exhaust eine vorgebbare Grenztemperatur T_Grenz,up übersteigt mit T_exhaust ≥ T_Grenz,up.

Therefore, variants are also advantageous in which

• - An exhaust gas temperature T _{exhaust is} determined in Abgasabführsystem, and
• - Air is introduced via the at least one opening in the Abgasabführsystem, if the exhaust gas temperature T _exhaust exceeds a predetermined limit temperature T _{limit, up} with T _exhaust ≥ T _{limit, up} .

• – eine Kühlmitteltemperatur T_coolant der flüssigkeitsgekühlten Brennkraftmaschine zu ermitteln, und
• – Luft via der mindestens einen Öffnung in das Abgasabführsystem einzubringen, falls die Kühlmitteltemperatur T_coolant eine vorgebbare Grenztemperatur T_Grenz,up übersteigt mit T_coolant ≥ T_Grenz,up.

In the case of liquid-cooled internal combustion engines, in which the at least one cylinder head has at least one integrated coolant jacket, it may be advantageous to

• To determine a coolant temperature T _{coolant of} the liquid-cooled internal combustion engine, and
• - Introduce air via the at least one opening in the Abgasabführsystem, if the coolant temperature T _coolant exceeds a predetermined limit temperature T _{limit, up} with T _coolant ≥ T _{limit, up} .

• – die Temperatur T ermittelt wird, und
• – Luft via der mindestens einen Öffnung nur dann in das Abgasabführsystem eingebracht wird, falls die Temperatur T eine vorgebbare Grenztemperatur T_Grenz,up übersteigt mit T ≥ T_Grenz,up und für eine vorgebbare Zeitspanne Δt_up größer ist als diese Grenztemperatur T_Grenz,up.

Advantageous are variants in which

• - The temperature T is determined, and
• - Air via the at least one opening is only introduced into the Abgasabführsystem if the temperature T exceeds a predetermined limit temperature T _{limit, up} with T ≥ T _{limit, up} and for a predetermined period of time .DELTA.t _{up is} greater than this limit temperature T _{limit, up} ,

The introduction of an additional condition for the introduction of air should help avoid too frequent or over-hasty activation of the _{curtain cooling} , in particular an activation of the _{curtain cooling} , for example, the cylinder head temperature T _cyl only briefly _exceeds a predetermined upper limit temperature T _{limit, up} and then falls again or fluctuates around the predetermined limit temperature, without exceeding would justify a cooling.

With this procedure, it is possible to respond appropriately to scenarios in which the cylinder head temperature T _cyl only briefly rises above the limit temperature T _{limit, up} and then drops again or fluctuates around the predetermined limit temperature.

It is advantageous to introduce into the air before introducing into the Abgasabführsystem a liquid. The liquid is introduced with the air flow as a carrier medium in the Abgasabführsystem, wherein the liquid is heated and evaporated, whereby the exhaust gas temperature is lowered.

The liquid used is preferably water. Water has the advantage over other coolants that it is non-toxic, readily available and inexpensive and also has a very high heat capacity, which is why water is suitable for the removal and absorption of large amounts of heat.

Advantageously, variants in which the air is introduced into the exhaust pipe, when an exhaust valve associated exhaust valve is in the closed position. Then the exhaust back pressure in the exhaust pipe is lower.

In the following, the invention will be described with reference to an embodiment of the internal combustion engine according to the 1 . 2a and 2 B explained. Hereby shows:

1 schematically a fragment of a cylinder head of a first embodiment of the internal combustion engine, partially cut, and

2a the outlet side valve seat ring in 1 illustrated embodiment, and

2 B the in 2a shown valve seat ring in section along the line AA.

1 schematically shows a fragment of a cylinder head 1 a first embodiment of the internal combustion engine, partially cut.

Shown is a cylinder 2 a liquid-cooled internal combustion engine in cross section. The cylinder head 1 has to form the liquid cooling an integrated coolant jacket 9 which belongs to a coolant-carrying coolant circuit.

The cylinder 2 has an inlet opening 3b for supplying air to the upstream one to an intake system 3 belonging suction line 3a followed. The cylinder 2 furthermore has an outlet opening 4b for removing the exhaust gases from the combustion chamber 2 via an exhaust gas removal system 4 , being attached to the outlet opening 4b downstream of an exhaust pipe 4a followed.

The exhaust pipes 4a the cylinder 2 lead to the formation of an exhaust manifold at a collection point of Abgasabführsystems 4 to an overall exhaust line together (not shown).

The outlet opening 4b of the cylinder 2 is an exhaust valve 7 associated with which a valve stem 7a and one at the combustion chamber end of the shaft 7a arranged valve plate 7b includes. In the illustrated closed position of the valve 7 becomes the valve plate 7b in a valve seat 8th stored, the present of one in the cylinder head 1 provided valve seat ring 8th is formed.

In the area of the valve seat ring 8th are several openings 5 provided, which are annular around the exhaust pipe 4a and thus around the outlet opening 4b spaced from each other, to the upstream compressed air supply lines 6 connect and the introduction of air into the Abgasabführsystem 4 for the purpose of cooling the cylinder head 1 serve. Thus, upstream of the collection point openings 5 in the exhaust system 4 intended.

2a shows the outlet side valve seat ring 8th the in 1 illustrated embodiment. 2 B shows this valve seat ring 8th in section along the line AA.

The used valve seat ring 8th has grooves which are spaced along the circumference and in the installed position of the ring 8th along with the rest of the cylinder head 1 the openings 5 train or represent. In the present case, the grooves or openings run 5 perpendicular to the central axis of the exhaust pipe and the valve stem.

LIST OF REFERENCE NUMBERS

1

 cylinder head

2

 Cylinder, combustion chamber

3

 intake system

3a

 suction

3b

 inlet port

4

 Abgasabführsystem

4a

 exhaust pipe

4b

 outlet

5

 opening

6

 Compressed air supply line

7

 outlet valve

7a

 valve stem

7b

 valve disc

8th

 Valve seat ring, valve seat

9

 Liquid cooling, coolant jacket

T _coolant

 Coolant temperature

T _cyl

 CHT

T _exhaust

 exhaust gas temperature

T _{border, up}

 predefinable upper limit temperature

Δt _up

specifiable minimum period for exceeding T _{limit, up}

Claims (15)

Internal combustion engine with at least one cylinder head ( 1 ), which has at least two cylinders ( 2 ), in which - each cylinder ( 2 ) at least one outlet opening ( 4b ) for discharging the exhaust gases via Abgasabführsystem ( 4 ), wherein at each outlet opening ( 4b ) an exhaust pipe ( 4a ), - each cylinder ( 2 ) at least one inlet opening ( 3b ) for supplying air via the intake system ( 3 ), and - the exhaust pipes ( 4a ) of at least two cylinders ( 2 ) to form an exhaust manifold at a collection point of the Abgasabführsystems ( 4 ) merge into an overall exhaust line, characterized in that - at least one opening upstream of the collection point ( 5 ) in the exhaust gas removal system ( 4 ), to which upstream a compressed air supply line ( 6 ) and the introduction of air into the Abgasabführsystem ( 4 ) for cooling the at least one cylinder head ( 1 ) serves. Internal combustion engine according to claim 1, characterized in that the exhaust pipes ( 4a ) the at least two cylinders ( 2 ) within the cylinder head ( 1 ) to the total exhaust line. Internal combustion engine according to claim 1 or 2, characterized in that at least one exhaust gas turbocharger, one in the intake system ( 3 ) arranged compressors and an im Exhaust gas removal system ( 4 Turbine is provided downstream, the turbine downstream of the collection point in the exhaust system ( 4 ) is arranged. Internal combustion engine according to claim 3, characterized in that the compressed air supply line ( 6 ) downstream of the compressor from the intake system ( 3 ) branches off. Internal combustion engine according to claim 3 or 4, wherein the compressor is provided with a blow-off line downstream of the compressor from the intake system ( 3 ) branches off, characterized in that the compressed air supply line ( 6 ) branches off from the blow-off line. Internal combustion engine according to one of the preceding claims, characterized in that in at least one exhaust pipe ( 4a ) at least two mutually spaced openings ( 5 ) are provided. Internal combustion engine according to claim 6, characterized in that the at least two openings ( 5 ) along a circumference of the exhaust pipe ( 4a ) are arranged spaced from each other. Internal combustion engine according to claim 6 or 7, characterized in that at least three openings ( 5 ) annularly around the exhaust pipe ( 4a ) are arranged spaced from each other. Internal combustion engine according to claim 8, characterized in that the at least three openings ( 5 ) annularly around the at least one outlet opening ( 4b ) at least one cylinder ( 2 ) are arranged spaced from each other. Internal combustion engine according to claim 9, wherein the at least one outlet opening ( 4b ) of a cylinder ( 2 ) an exhaust valve ( 7 ), which in the closed position in a valve seat ( 8th ) and the outlet opening ( 4b ), characterized in that the at least three openings ( 5 ) in the region of the valve seat ( 8th ) are arranged, wherein the exhaust valve ( 7 ) the at least three openings ( 5 ) closes in the closed position. Internal combustion engine according to one of the preceding claims, characterized in that the compressed air supply line ( 6 ) to the at least one opening ( 5 ) at the exhaust-side end an acute angle α with the respective exhaust pipe ( 4a ) forms with α <45 °. Internal combustion engine according to one of the preceding claims, characterized in that in the compressed air supply line ( 6 ) A shut-off element is arranged. Internal combustion engine according to one of the preceding claims, characterized in that the at least one opening ( 5 ) is designed as a nozzle. Internal combustion engine according to one of the preceding claims, characterized in that the compressed air supply line ( 6 ) at least partially in the at least one cylinder head ( 1 ) is integrated. Internal combustion engine according to one of the preceding claims, characterized in that the at least one opening ( 5 ) in an exhaust pipe ( 4a ) of the exhaust removal system ( 4 ) provided in the at least one cylinder head ( 1 ) is integrated.

Images