DE102010036581A1 - Liquid-cooled combustion engine for motor car, has shut-off element arranged upstream to steering valve and in feed line of heating circuit, where shut-off element is controlled by engine controller based on coolant temperature - Google Patents

Abstract

The engine (1) has a heating circuit (9) provided in a coolant-operating heating part (11). An automatic steering valve (7) comprises a temperature-reactive element (7a) subjected with coolant. A return line (6) is connected either with a supply line (4) or separated from the supply line. An electrical actuatable shut-off element (12) is arranged upstream to the steering valve and in a feed line (10) of the heating circuit. The electrical actuatable shut-off element is controlled by an engine controller (13) based on coolant temperature. An independent claim is also included for a method for operating a liquid-cooled combustion engine.

Description

• – einem Kühlmittelkreislauf umfassend mindestens einen im Zylinderkopf integrierten Kühlmittelmantel, eine Zuführleitung zur Versorgung des Kühlmittelmantels mit Kühlmittel, eine Abführleitung zum Abführen des Kühlmittels und eine Rückführleitung, welche von der Abführleitung abzweigt und via einem selbsttätig – temperaturabhängig – steuernden Ventil in die Zuführleitung einmündet und in der ein Wärmetauscher vorgesehen ist, und
• – einem Heizungskreislauf, der eine Versorgungsleitung umfaßt, die von der Abführleitung abzweigt und via dem selbsttätig steuernden Ventil in die Zuführleitung einmündet und in der eine kühlmittelbetriebene Heizung vorgesehen ist, wobei das selbsttätig steuernde Ventil ein mit Kühlmittel beaufschlagtes temperatur-reaktives Element aufweist und die Rückführleitung in Abhängigkeit von der Kühlmitteltemperatur T_{coolant,valve} am Element entweder mit der Zuführleitung verbunden oder von der Zuführleitung getrennt ist, wohingegen die Versorgungsleitung mittels Ventil von der Zuführleitung nicht trennbar ist.

The invention relates to a liquid-cooled internal combustion engine with at least one cylinder head and

• A coolant circuit comprising at least one coolant jacket integrated in the cylinder head, a supply line for supplying the coolant jacket with coolant, a discharge line for discharging the coolant and a return line which branches off from the discharge line and opens into the supply line via an automatically temperature-dependent-controlling valve; a heat exchanger is provided, and
• - A heating circuit comprising a supply line which branches off from the discharge line and opens via the automatically controlling valve in the supply line and in which a coolant-driven heater is provided, wherein the automatically controlling valve has a temperature-responsive element acted upon with coolant and the return line depending on the coolant temperature T _{coolant valve} on the element is either connected to the supply line or separated from the supply line, whereas the supply line by means of valve from the supply line is not separable.

Furthermore, the invention relates to a method for operating such an internal combustion engine.

An internal combustion engine of the above type is used for example as a drive for a motor vehicle. In principle, it is possible to carry out the cooling of the internal combustion engine in the form of air cooling or liquid cooling. Due to the higher heat capacity of liquids can be dissipated with a liquid cooling much larger amounts of heat than is possible with an air cooling.

The thermal load of the motors is steadily increasing. This is also due to the fact that internal combustion engines are increasingly charged and - with the aim of a dense packaging - more and more components, such as the exhaust manifold, are integrated into the cylinder head or cylinder block, whereby the thermal load of the motors, d. H. the internal combustion engine, grows.

For this reason, internal combustion engines are increasingly equipped with liquid cooling according to the prior art.

The liquid cooling requires the equipment of the cylinder head with a coolant jacket, d. H. the arrangement of the coolant through the cylinder head leading coolant channels. The heat does not have to be directed to the cylinder head surface, as in the case of air cooling, in order to be dissipated. The heat is already in the interior of the cylinder head to the coolant, usually mixed with additives added water. The coolant is thereby conveyed by means of a pump arranged in the supply line of the coolant circuit, so that it circulates. The heat emitted to the coolant heat is dissipated in this way from the interior of the cylinder head via the discharge line and removed from the coolant outside the cylinder head again, which can be done in different ways. Like the cylinder head, the cylinder block can be equipped with one or more coolant jackets.

The coolant circuit is completed by a return line which branches off from the discharge line and opens into the supply line and via which the coolant heated in the cylinder head is returned to the coolant inlet side. The discharge and the supply line need not represent lines in the strict sense, but may be part of the coolant jacket or be formed in the form of a coolant inlet housing or coolant outlet housing.

In the return line, a heat exchanger is provided which removes heat from the coolant again. To provide the heat exchanger under all operating conditions, especially when the vehicle is stationary and at low vehicle speeds, a sufficiently high air mass flow and to support the heat transfer in principle, the cooling systems of modern motor vehicle engines are increasingly equipped with powerful fan motors that drive a fan or set in rotation. The fan motors are usually operated electrically and are preferably infinitely controllable with different loads or speeds.

The coolant can after flowing through the cylinder head, d. H. downstream of the cylinder head, heat also be extracted by further use.

In the internal combustion engine object of the present invention, there is provided a coolant-operated heater that uses the coolant heated in the cylinder head to heat the air supplied to the passenger compartment of the vehicle, and the temperature of the coolant decreases.

The heating circuit includes a supply line, which branches off from the discharge line and opens into the supply line and in which a coolant-operated heater is provided.

Consequently, the coolant heated in the cylinder head is deprived of heat not only in the heat exchanger of the coolant circuit but also as it flows through the heating circuit. The heating circuit can therefore also be referred to as a small cooling circuit or small coolant circuit. Nevertheless, in the context of the present invention, a distinction is made between the coolant circuit on the one hand, whose primary function is the cooling of the cylinder head using the heat exchanger, and the heating circuit on the other hand, which serves to heat the air supplied to the interior, even if both circuits partially use the same lines , For example, the supply and the discharge line.

It is not the objective and the object of liquid cooling to extract the largest possible amount of heat from the internal combustion engine under all operating conditions. Rather, a needs-based control of the liquid cooling is sought, which in addition to the full load and the operating modes of the internal combustion engine takes into account, in which it is more advantageous to extract less or as little heat as possible from the internal combustion engine.

It should be noted in this context that it is always endeavor to minimize the fuel consumption of an internal combustion engine. In addition to an improved, d. H. more effective, combustion is the reduction of friction in the focus.

With regard to the latter, rapid heating of the engine oil, especially after a cold start, is expedient. Rapid heating of the engine oil during the warm-up phase of the engine provides for a correspondingly rapid decrease in the viscosity of the oil, resulting in a reduction in friction, especially in the oil-powered bearings, such as the crankshaft bearings.

Various concepts are known from the prior art, which seek to reduce the friction loss by rapid heating of the engine oil. The oil can be actively heated, for example by means of external heating device. A heater is but in terms of fuel use an additional consumer, which is a reduction in fuel consumption. Other concepts include storing the engine-heated engine oil in an insulated container and using it on a restart, whereby the oil heated during operation can not be kept indefinitely at a high temperature. According to another concept, a coolant-operated oil cooler is used in the warm-up phase and used for heating the oil, which in turn requires rapid heating of the coolant.

In principle, rapid heating of the engine oil to reduce friction losses can also be achieved by rapid heating of the internal combustion engine itself, which in turn is assisted by d. H. forced, is that the internal combustion engine during the warm-up phase as little heat is removed.

In this respect, the warm-up phase of the internal combustion engine after a cold start is an example of an operating mode in which it is advantageous to extract heat from the internal combustion engine as little as possible, ideally none.

A control of the liquid cooling, in which for the purpose of rapid heating of the internal combustion engine, the heat extraction is reduced after a cold start, can be realized by the use of a self-dependent temperature-controlling valve, which is often referred to in the art abbreviated as a thermostat.

This automatically controlling valve has a temperature-responsive element acted upon by coolant, the return line being connected to the supply line as a function of the coolant temperature T _{coolant valve} on the element either in the open position of the valve or being separated from the supply line in the closed position of the valve. The supply line of the heating circuit is continuously connected to the supply line with the interposition of the automatically controlling valve.

The supply line passes through the valve to pressurize the temperature-responsive element with coolant from the heating circuit when the valve is closed. When the valve is closed, for example after a cold start, the coolant flow is prevented via the coolant circuit or heat exchanger and the coolant circulates in the heating circuit, wherein the temperature-reactive element of the valve is acted upon by the coolant of the heating circuit. The coolant flow through the cylinder head is reduced due to the closed valve, whereby on the one hand, the heat transfer due to convection is reduced and on the other hand, the comparatively small, freely circulating coolant quantity can be heated faster. With the deactivation of the coolant circuit, the heat removal in the radiator is eliminated.

If the temperature T _{coolant, valve} of the coolant circulating in the heating circuit reaches or exceeds a certain threshold temperature T _{coolant, valve, therhold} at the temperature-reactive element _{, the valve} opens and _exceeds the valve and the return line is connected to the Feed line connected. Now coolant flows from the coolant circuit via the valve into the supply line and mixes with the originating from the heating circuit coolant flow. The coolant flow rate through the cylinder head increases and consequently the amount of heat extracted from the cylinder head increases, with the temperature T _{coolant of} the coolant decreasing due to the additional and colder coolant from the cooling circuit, forcibly leading to a higher temperature difference between the coolant and the cylinder head.

It should be _noted that if the temperature T _{coolant, valve} falls below the threshold temperature T _{coolant, valve, therhold, the element will be acted upon by the total} coolant flow resulting from the mixing of the two coolant flows in the valve, which will cause the valve to re-close , As a rule, the thermostat opens and closes several times during warm-up.

It would be advantageous, after a cold start of the internal combustion engine, the circulation of the coolant in the heating circuit, d. H. to completely suppress the flow of coolant to adjust in this way the heat dissipation due to convection. The coolant would then not flow at least at the beginning of the warm-up phase, but rather stand in the lines and in the coolant jacket of the cylinder head, which further accelerates the heating of the coolant and the heating of the brake motor. Such a control would additionally promote the heating of the engine oil and further reduce the friction loss.

In addition, in principle, a control of the liquid cooling is desirable with which not only the circulating coolant quantity or the coolant flow rate can be reduced after a cold start in the warm-up phase to accelerate the heating of the coolant or the engine oil, but also on the heat balance of can be influenced to the operating temperature heated internal combustion engine.

A first further development of the described control of a liquid cooling provides to replace the conventional thermostat by a map-controlled thermostat, which in contrast to the conventional thermostat is not characterized by a specific fixed opening temperature, but the electric heating a map-specific virtual opening temperature can be impressed.

Thus, the - depending on the coolant temperature - automatically controlling valve is replaced by a motor control map-specific controlled valve, so that the coolant flows and thus the extracted heat and the coolant temperature are variable and can be adjusted as needed.

A map-controlled thermostat, ie valve, likewise has a temperature-responsive element acted upon by coolant, which, in principle, in turn has a component-specific opening temperature. However, the temperature-responsive element is electrically heated, so that the thermostat is controlled not only by the prevailing at the element coolant temperature T _coolant , but also by means of electrical heating or power supply by the engine control. When the element is heated by means of heating, the element is impressed from the outside by a virtual coolant temperature which is higher than the coolant temperature actually present at the element.

A map-controlled thermostat makes it possible to design the component-specific opening temperature to the part-load operation in order to realize a part-load operation coolant temperature T _coolant of 95 ° C to 110 ° C. This unacceptable for higher loads and unusually high opening temperature is then corrected with increasing load by electrical heating, ie by introducing electrical energy in such a way that the thermostat opens at lower temperatures present on the element, for example, the usual for higher loads Coolant temperature from 85 ° C to 95 ° C sets.

An automatically controlled valve with a fixed component-specific opening temperature must meet all load conditions and therefore have a designed for high loads opening temperature, which is relatively low and leads to lower coolant temperatures even in partial load operation.

Different coolant temperatures for different load conditions are extremely advantageous because the heat transfer in the cylinder head is determined not only by the amount of coolant passed, but also significantly by the temperature difference between the component and coolant.

A higher coolant temperature in part-load operation is synonymous with a small temperature difference between the coolant and the cylinder head. A low heat transfer at low and medium loads is the result. This increases the efficiency in partial load operation. Since an internal combustion engine is generally operated in the partial load range after a cold start, the increased coolant temperature also offers advantages in terms of reducing the friction in the warm-up phase.

In addition to the statements with regard to the map-controlled thermostat, it should be noted that from the prior art embodiments are known which prevent the circulation of the coolant in smaller coolant circuits, for example the heating circuit, as soon as the coolant circuit is opened by the radiator.

The high costs of the map-controlled thermostat are contrary to a wide application in series production. Another disadvantage is seen in the complex control of the thermostat and the fact that in case of failure or failure of the electric heater, an opening of the valve only occurs when the coolant reaches the temperature-reactive element, the comparatively high component-specific opening temperature, causing it a thermal overload of the internal combustion engine can come.

The present invention is therefore also an internal combustion engine whose liquid cooling is equipped with a function of the coolant temperature automatically controlling valve, which is characterized by a specific constant opening temperature.

Against the background of the above, it is the object of the present invention to provide a liquid-cooled internal combustion engine according to the preamble of claim 1, the liquid cooling is designed such that both the heat balance of the engine in the warm-up phase as well as the heat balance of the heated internal combustion engine Advantageous influence can be taken.

A further sub-task of the present invention is to show a method for operating such an internal combustion engine.

• – einem Kühlmittelkreislauf umfassend mindestens einen im Zylinderkopf integrierten Kühlmittelmantel, eine Zuführleitung zur Versorgung des Kühlmittelmantels mit Kühlmittel, eine Abführleitung zum Abführen des Kühlmittels und eine Rückführleitung, welche von der Abführleitung abzweigt und via einem selbsttätig – temperaturabhängig – steuernden Ventil in die Zuführleitung einmündet und in der ein Wärmetauscher vorgesehen ist, und
• – einem Heizungskreislauf, der eine Versorgungsleitung umfaßt, die von der Abführleitung abzweigt und via dem selbsttätig steuernden Ventil in die Zuführleitung einmündet und in der eine kühlmittelbetriebene Heizung vorgesehen ist, wobei das selbsttätig steuernde Ventil ein mit Kühlmittel beaufschlagtes temperatur-reaktives Element aufweist und die Rückführleitung in Abhängigkeit von der Kühlmitteltemperatur T_{coolant,valve} am Element entweder mit der Zuführleitung verbunden oder von der Zuführleitung getrennt ist, wohingegen die Versorgungsleitung mittels Ventil von der Zuführleitung nicht trennbar ist,

die dadurch gekennzeichnet ist, dass

• – stromaufwärts des selbsttätig steuernden Ventils ein elektrisch betätigbares Absperrelement in der Versorgungsleitung des Heizungskreislaufs angeordnet ist, das mittels Motorsteuerung in Abhängigkeit von einer Temperatur T_coolant des Kühlmittels steuerbar ist.

The first sub-task is solved by a liquid-cooled internal combustion engine with at least one cylinder head and

• A coolant circuit comprising at least one coolant jacket integrated in the cylinder head, a supply line for supplying the coolant jacket with coolant, a discharge line for discharging the coolant and a return line which branches off from the discharge line and opens into the supply line via an automatically temperature-dependent-controlling valve; a heat exchanger is provided, and
• - A heating circuit comprising a supply line which branches off from the discharge line and opens via the automatically controlling valve in the supply line and in which a coolant-driven heater is provided, wherein the automatically controlling valve has a temperature-responsive element acted upon with coolant and the return line depending on the coolant temperature T _{coolant valve} on the element is either connected to the supply line or separated from the supply line, whereas the supply line is not separable by means of valve from the supply line,

which is characterized in that

• - Is arranged upstream of the self-controlling valve, an electrically actuated shut-off in the supply line of the heating circuit, which is controllable by means of motor control function of a temperature T _{coolant of} the coolant.

The internal combustion engine according to the invention has an electrically operable shut-off element in the supply line, with which the heat transfer in the cylinder head can be influenced both in the warm-up phase and after completion of the warm-up phase.

Closing the shut-off element after a cold start prevents circulation of the coolant in the heating circuit. The coolant flow is thereby completely stopped because a coolant flow through the heat exchanger acting as a cooler does not yet take place due to the low coolant temperature and the closed valve.

Characterized in that the coolant is brought to a stop in the cylinder head by closing the shut-off after a cold start, the heating of the coolant and the heating of the internal combustion engine are accelerated. Due to the lower heat extraction in the cylinder head, the engine oil heats up faster. The friction is thereby reduced, which has an advantageous effect on fuel consumption.

By suitably activating the shut-off element, it is possible to influence the coolant flows even after the warm-up phase has ended. H. the coolant flow rate and thus the coolant temperature and the heat balance of the heated internal combustion engine.

In a warm-running internal combustion engine different coolant temperatures for different load conditions can be realized in this way, although - in contrast to the prior art - an automatically controlling valve and no map-controlled valve is used.

The internal combustion engine according to the invention makes it possible to control the coolant temperatures in the Part load operation to raise, which can improve the efficiency in the partial load range.

For this purpose, the shut-off element is intermittently opened at low and medium loads, with alternating short opening and closing phases. The shut-off is therefore not open continuously. Rather, the opening phases are interrupted by closing phases.

The control of the shut-off element in detail, in particular the intermittent clocked opening of the shut-off element as a function of the coolant temperature T _coolant , will be described in detail in connection with the method _according to the invention. In particular, liquid-cooled internal combustion engines in which the shut-off element can be controlled by means of motor control as a function of a temperature T _{coolant, circuit of} the coolant in the coolant _circuit are advantageous. The control requires the storage of maps in the engine control.

The internal combustion engine according to the invention thus solves the first sub-task on which the invention is based. There is provided an internal combustion engine, the liquid cooling is designed such that both the heat balance of the internal combustion engine in the warm-up phase as well as the heat balance of the heated internal combustion engine can be advantageously influenced.

The proposed concept is also suitable for retrofitting already on the market internal combustion engines.

In addition to the coolant circuit and the heating circuit further circuits or heat exchangers can be provided.

On the intake side of an internal combustion engine, a charge air cooler is often arranged. The intercooler lowers the temperature of the intake fresh air or of the sucked fresh mixture and thus increases the density of the cylinder fresh charge. In this way, the 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.

The cooling of the charge air by means of intercooler is used primarily to increase the performance of the internal combustion engine. The air required for the combustion process is compressed due to the cooling, whereby each cylinder per cycle can be supplied with a larger air mass. As a result, the fuel mass and thus the medium pressure can be increased.

In addition, 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 not only an excess of air but also 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 lowering 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%. In order to realize these high recycling rates, cooling of the exhaust gas to be recirculated, ie compression of the exhaust gas by cooling, is absolutely necessary in order to increase the density of the recirculated exhaust gas. The Brernnkraftmaschine 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.

Although it is generally advantageous to heat the engine oil as quickly as possible after a cold start in order to reduce the friction, the oil of a warmed up internal combustion engine usually has to be cooled, as overheating of the engine oil leads to premature aging of the oil and deterioration the lubricating properties leads.

In order to maintain a maximum permissible oil temperature, the heat release via the oil sump by means of heat conduction and natural convection is often no longer sufficient, so that an oil cooler is provided, which can be coolant-driven, ie the heat extracting the oil using the coolant. A coolant-driven oil cooler also offers the possibility of engine oil in the Warm-up phase using the coolant to heat.

Both embodiments of the internal combustion engine in which the oil cooler is provided parallel to the coolant-operated heater and also embodiments in which the oil cooler is arranged in series with the coolant-operated heater are advantageous.

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

Embodiments of the internal combustion engine in which a sensor is provided for the metrological detection of the coolant temperature T _coolant are advantageous. The sensor-detected coolant temperature is provided to the engine controller as an input.

The metrological detection of the coolant temperature T _coolant by means of a sensor is presently unproblematic because the coolant has moderate temperatures even when the engine has warmed up, for example in comparison to the high temperatures of the combustion gases. The cooling circuit of an internal combustion engine also offers a variety of possibilities, ie many points, for the arrangement of a sensor, without the functioning of the liquid cooling would be affected.

Although a mathematical determination of the coolant temperature exclusively by means of simulation, in which dynamic heat models and kinetic models are used to determine the heat of reaction generated during combustion, is basically a way to determine the coolant temperature T _cooling , but not the preferred approach, even if the simulation calculation requires no further components, in particular no sensors, in order to determine the temperature, which is favorable in terms of cost. The coolant temperature T _cooling determined by means of simulation is merely an estimated value, which would adversely affect the quality of the control of the liquid cooling.

For estimating the coolant temperature T _cooling, it is also possible to use a component temperature, in particular a cylinder head temperature, which, for example, in turn is detected by means of a sensor. According to this variant, the temperature of the coolant is determined indirectly - using a different temperature - which is basically another way to determine the coolant temperature.

If the coolant temperature is detected by means of a sensor, embodiments are advantageous in which the sensor for detecting the coolant temperature T _{cooling is arranged} adjacent to an outlet of the coolant circuit from the at least one cylinder head.

The arrangement of the sensor downstream of the cylinder head, according to the above embodiment concretely in the area of the coolant outlet from the cylinder head, ensures that the temperature is detected at a point of the cooling circuit, at which the coolant has already undergone a significant increase in temperature, since it is the cylinder head flowed through and absorbed heat. This is advantageous since the coolant temperature is frequently regulated or should be regulated to a maximum permissible coolant temperature.

With the above aspect in mind, it is particularly advantageous to determine the temperature at the point in the refrigeration cycle where the refrigerant reaches the maximum temperature. For the same reason, variants are also advantageous in which the sensor is arranged close to the highest point of the coolant circuit or coolant jacket, since the vaporized, superheated coolant collects at the highest point of the circuit and preferably there the venting of the cooling circuit is made.

According to an alternative variant of the method, the sensor for detecting the coolant temperature T _{coolant can} also be arranged adjacent to an inlet of the coolant circuit into the at least one cylinder head.

The inlet temperature of the coolant can also be used to determine the coolant temperature T _coolant at another point of the cooling circuit, ie to estimate.

In principle, it is possible to measure the temperature at one point and to transform this temperature in order to determine the coolant temperature at another location.

From the above it follows that embodiments of the internal combustion engine are advantageous in which the sensor is provided for metrological detection of the coolant temperature T _coolant in the coolant circuit downstream of the at least one cylinder head and upstream of the heat exchanger in the coolant circuit.

Advantageous embodiments of the internal combustion engine, in which a vent line is provided, the upstream of the Shut-off opens into the supply line and in which a surge tank is arranged.

The guide or the connection of the vent line according to the above type proves to be extremely advantageous in the warm-up phase. Closing the shut-off element according to the invention after a cold start with the aim of preventing the circulation of the coolant in the heating circuit also stops the coolant flow in the deaeration system. As a result, the amount of coolant circulating freely and to be heated in the warm-up phase is further reduced by the amount present in the venting circuit, in particular in the expansion tank, which in one case may be one and a half to two liters.

Embodiments of the internal combustion engine in which the heat exchanger of the coolant circuit is a radiator are advantageous. The equipment of the heat exchanger with a fan ensures a sufficiently high air mass flow even at a standstill and at low vehicle speeds.

Embodiments of the internal combustion engine in which a pump for conveying the coolant is arranged in the supply line are advantageous, so that the coolant circulates.

Embodiments of the internal combustion engine in which the temperature-responsive element of the valve is a wax element are advantageous.

The second of the invention underlying subtask, namely to show a method for operating an internal combustion engine according to one of the aforementioned embodiments, is achieved by a method in which the electrically actuable shut-off depending on a temperature T _{coolant of} the coolant and the load p _me Internal combustion engine is controlled, in such a way that the shut-off element is intermittently opened at the end of the warm-up phase at low and medium loads.

The comments made in connection with the internal combustion engine according to the invention also apply to the inventive method.

With the method according to the invention, after the end of the warm-up phase, influence is exerted on the heat balance of the internal combustion engine, ie. H. on the heat transfer in the cylinder head. The criteria by means of which the conclusion of the warm-up phase is determined as the decisive prerequisite for the initiation of the method according to the invention are determined in advance.

Advantageously, the specification of a certain minimum temperature T _min , which must have reached the coolant, so that the warm-up phase is considered completed. The minimum temperature T _min can be deposited for comparison purposes, for example in the engine control. Alternatively or additionally, a period of time, ie, a minimum operating time t _min , are given, via which the internal combustion engine must have been operated since the start or restart at least, ie which must have elapsed so that it may be assumed that a warm-running internal combustion engine.

In an analogous manner, it is to be determined what is to be regarded as a low and medium load so that the partial load range in which the method according to the invention is used is clearly defined. The lower and upper limits of the associated part-load range can be specified in percent, with the full load is suitable as a reference. A determination of the load range can be made several times for different speeds or even once, then possibly with the rated load as a reference. The definition of the load range explains the dependence of the control of the shut-off element on the load p _me .

By suitably driving the shut-off element, namely the intermittent, d. H. the repeatedly interrupted by closing, opening the shut-off element is directly influenced on the coolant flow of the heating circuit and thus on the coolant flow through the cylinder head.

The shut-off is not continuously opened in the partial load range, but phase-closed again and again, so that alternate opening phases and closing phases and the amount of coolant passed through the cylinder head in the middle is reduced. The result is an increase in the coolant temperature. Closing the shut-off element sets the circulation in the heating circuit and no coolant flows via the shut-off element or supply line into the cylinder head. With the valve still closed, d. H. when the coolant circuit is still closed, the coolant flow comes to a complete halt by closing the shut-off element.

The inventive method allows the increase in the coolant temperature of the heated internal combustion engine in the partial load range. The heat transfer in the cylinder head also correlates with the temperature difference between the component and the coolant. A higher coolant temperature is equivalent to a small temperature difference between the coolant and the cylinder head. An increased coolant temperature thus leads to a lower heat transfer, whereby the efficiency is improved in the partial load operation of the internal combustion engine.

The fact that the method according to the invention leads to an improvement in the efficiency especially in part-load operation is particularly advantageous when it is taken into account that spark-ignited internal combustion engines have a comparatively poor efficiency precisely in this load range because of their load regulation.

The method according to the invention also makes it possible to close the shut-off element after a cold start. At this time, the valve is still closed due to the low coolant temperature. The circulation of the coolant is thus completely prevented in the warm-up phase.

As already explained several times and in detail, the heating of the coolant and the heating of the internal combustion engine are thereby accelerated. The engine oil heats up faster and the friction loss is reduced, which reduces fuel consumption.

For the reasons mentioned above, embodiments are also advantageous in the context of the method according to the invention, in which the shut-off element is closed or remains after a cold start of the internal combustion engine in the warm-up phase.

Process variants are advantageous in which the shut-off element is opened after completion of the warm-up phase when the instantaneous load p _{me warmly} exceeds a predefinable load p _{me, threshold} .

At high loads, especially at full load, the greatest possible heat dissipation is sought in order to reliably avoid thermal overloading of the internal combustion engine. The goal here is the greatest possible coolant throughput, even if the coolant temperature itself decreases.

With the method according to the invention, different coolant temperatures for different load states can be realized in a warm-running internal combustion engine and this without using the map-controlled valve known from the prior art.

Embodiments of the method in which the coolant temperature T _{coolant is detected} by means of a sensor are advantageous.

Process _variants in which the coolant temperature T _{coolant, circuit} in the coolant circuit downstream of the at least one cylinder head and upstream of the heat exchanger is detected are advantageous.

With regard to the two last-mentioned process variants, reference is made to what has been said in connection with the internal combustion engine according to the invention.

Embodiments of the method are advantageous in which the electrically actuable shut-off element is controlled as a function of the temperature T _{coolant, circuit of} the coolant in the coolant circuit and the load p _{me of} the internal combustion engine.

Embodiments of the method in which the intermittent opening of the shutoff element is pulse width modulated at low and medium loads are advantageous.

Also advantageous are embodiments of the method in which the intermittent opening of the shut-off is performed clocked, wherein a clock includes a closing phase and an opening phase and having a constant period of time.

A clocked opening can be carried out in an advantageous manner with a fixed uniform clock or with a variable clock. The differences exist with regard to the division of the clock in opening and closing phases.

On the one hand, embodiments of the method are advantageous in which the intermittent opening is performed with a constant uniform clock, so that the shares of the closing phase and the opening phase are the same at the clock at each clock. According to a specific embodiment, the closing phase and the opening phase are the same, d. H. of equal length.

On the other hand, process variants are advantageous in which the intermittent opening is carried out with a variable cycle, in which the shares of the closing phase and the opening phase are variable on the clock.

This variant allows a change in the distribution of cycle by cycle, in particular as a function of the instantaneous coolant temperature T _coolant , and thus a needs-based adjustment of the distribution to the current coolant temperature T _coolant . In this connection, embodiments of the method are advantageous in which the portions of the closing phase and the opening phase are determined at the cycle as a function of the temperature difference ΔT _coolant by which the instantaneous coolant temperature T _coolant of a specifiable guide value T _{coolant, threshold} deviates, where: ΔT _coolant = T _{coolant, threshold} - T _coolant

A variable stroke makes it possible to increase the proportion of the closing phase in order to increase the coolant temperature or to increase the proportion of the opening phase in order to lower the coolant temperature.

Embodiments of the method in which the shut-off element is opened in the warm-up phase are advantageous if the instantaneous load p _me exceeds a predefinable load p _{me, threshold, cold} .

Although - as described above - the shut-off after a cold start of the internal combustion engine preferably be closed or remain to accelerate the heating of the engine oil. In unfavorable operating conditions, it may also be advantageous to open the shut-off exceptionally in the warm-up phase to protect the engine from irreparable damage, if, for example, after a cold start unfavorably high loads are required or the power consumption is high.

Advantageous are process variants in which water is used as the coolant. As a rule, the water is mixed with additives. 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 removal of very large amounts of heat, which is generally considered advantageous.

But can also be advantageous process variants in which oil is used as a coolant. Compared to the use of water, oil as a coolant has the advantage that it is not corrosive, rather even offers corrosion protection and unlike water with - in particular moving - components can easily come into contact without the functioning of the engine would be at risk ,

In addition, oil is used anyway as a process fluid and passed through the cylinder head or the block to supply various consumers, in particular the crankshaft and the camshaft, with oil.

The lower heat capacity of oil compared to water leads to a lower heat removal, which is advantageous after a cold start. The formation of the liquid cooling using motor oil as a refrigerant accelerates the heating of the oil during the warm-up phase.

In a cylinder head with at least two coolant jackets, two different coolant can be used. The cylinder head has two independent coolant circuits, each having at least one coolant jacket and operated with different coolants. An outlet side coolant jacket could be operated with water and an inlet side coolant jacket with oil as the coolant.

In the following, the invention is based on the 1 to 3 described in more detail. Hereby shows:

1 schematically a first embodiment of the internal combustion engine,

2 as a diagram, the curve of the coolant temperature T _{coolant, circuit} , the circuit state of the shut-off element and the vehicle speed v over the time t, and

3 a section of the in 2 displayed diagram for the time window of 800 to 900 seconds.

1 schematically shows a first embodiment of the internal combustion engine 1 , The internal combustion engine 1 is equipped with liquid cooling. A coolant circuit 3 includes one in the cylinder head 2 integrated coolant jacket, a supply line 4 for supplying this coolant jacket with coolant, a discharge line 5 for discharging the coolant and a return line 6 , which from the discharge line 5 branches off and via an automatically controlling valve 7 in the supply line 4 opens and in a designed as a radiator heat exchanger 8th is arranged. To pump the coolant is a pump 15 provided in the supply line 4 is arranged.

The automatically controlling valve 7 has a temperature-sensitive element charged with coolant 7a , Depending on the coolant temperature T _{coolant, valve} on the element 7a becomes the return line 6 either with the supply line 4 connected or from the supply line 4 separated. When the valve is closed 7 is the element 7a exclusively with from the heating cycle 9 applied coolant.

The heating circuit 9 includes a supply line 10 coming from the discharge line 5 branches off and via the self-acting valve 7 in the supply line 4 opens and in which a coolant driven heater 11 is arranged. The supply line 10 is not by switching the valve 7 from the supply line 4 separable. Both lines 4 . 10 are in constant contact.

Upstream of the automatically controlled valve 7 is an electrically operated shut-off 12 in the supply line 10 of the heating circuit 9 arranged by means of motor control 13 is controlled in dependence on the coolant temperature T _coolant . For metrological detection of the coolant temperature T _{coolant, circuit} in the coolant circuit 3 is downstream of the cylinder head 2 a sensor 14 in the discharge line 5 arranged, the coolant temperature T _{coolant, circuit} as an input to the engine control 13 supplies.

2 schematically shows a diagram of the course of the coolant temperature T _{coolant, circuit} , the circuit state of the shut-off element and the vehicle speed v over the time t.

The coolant temperature T _{coolant, circuit} in the coolant circuit is on the left ordinate in ° Celsius and the time t is plotted on the abscissa in seconds. At the right edge of the diagram, the two switching states of the shut-off element are indicated, so that the diagram can also be seen at what time the shut-off is on or on, that is in the closed position or in the open position (see curve A).

Starting from a cold start of the internal combustion engine, the NEDC cycle is completed, which covers 1180 seconds and is also used to determine the pollutant emissions in order to check compliance with the legally regulated pollutant concentrations. The associated course v (t) of the vehicle speed v over the time t can be found in the diagram.

The temperature T _{coolant of} the coolant increases continuously in the warm-up phase. The shut-off element is closed during the warm-up phase.

If the coolant reaches a predetermined minimum temperature T _min , which in the present case is about 98 ° C, the warm-up phase is considered completed. In this case, the minimum temperature T _min corresponds to a minimum operating time t _min of 470 seconds.

After completion of the warm-up phase, the electrically actuable shut-off is controlled in dependence on the coolant temperature T _coolant , wherein the shut-off is opened intermittently, that is, alternately opened and closed.

The intermittent opening of the shutoff is performed clocked. A clock spans a constant period of time and consists of closing phase and opening phase. At the in 2 illustrated method variant, the intermittent opening is carried out with a variable cycle, in which the proportions of the closing phase and the opening phase vary in the clock, depending on the current coolant temperature T _coolant .

The result of the intermittent opening is a comparatively high coolant temperature T _coolant in the part-load operation, which in the present case corresponds to the cylinder head outlet temperature and is on average about 105 ° C.

3 shows a section of the in 2 displayed diagram for the time window of 800 to 900 seconds. It should only be supplementary to 2 For that reason, reference is made to FIG 2 ,

It can be seen from the detail that the timing of the shut-off element of the shape, d. H. can be so fast that the shut-off element does not fully reach the closed position or the open position and previously made a change in direction.

LIST OF REFERENCE NUMBERS

1

liquid-cooled internal combustion engine

2

cylinder head

3

Coolant circuit

4

feed

5

discharge

6

Return line

7

self-controlling valve, thermostat

7a

temperature-reactive element

8th

Heat exchanger, radiator

9

Heating circuit

10

supply line

11

heater

12

shut-off

13

motor control

14

sensor

15

pump

p _me

momentary load

p _{me, threshold, cold}

predefinable load for the internal combustion engine in the warm-up phase

p _{me, threshold, warm}

specifiable load for the internal combustion engine after the warm-up phase

T _coolant

Temperature of the coolant

T _{coolant, circuit}

Temperature of the coolant in the coolant circuit

T _{coolant, heating}

Temperature of the coolant in the heating circuit

T _{coolant, valve}

Temperature of the coolant at the thermally-reactive element of the valve

T _{coolant, threshold}

Guideline for the coolant temperature

ΔT _coolant

Temperature difference between T _coolant and T _{coolant, threshold}

T _min

minimum temperature

t

Time

_min

Minimum operating time

v

vehicle speed

Claims (14)

Liquid-cooled internal combustion engine ( 1 ) with at least one cylinder head ( 2 ) and - a coolant circuit ( 3 ) comprising at least one in the cylinder head ( 1 ) integrated coolant jacket, a supply line ( 4 ) for supplying the coolant jacket with coolant, a discharge line ( 5 ) for discharging the coolant and a return line ( 6 ), which from the discharge line ( 5 ) and via a self-dependent - temperature-dependent - controlling valve ( 7 ) in the supply line ( 4 ) and in which a heat exchanger ( 8th ), and - a heating cycle ( 9 ), which is a supply line ( 10 ) separated from the discharge line ( 5 ) and via the automatically controlling valve ( 7 ) in the supply line ( 4 ) and in which a coolant-operated heater ( 11 ) is provided, wherein the automatically controlling valve ( 7 ) a coolant-loaded temperature-reactive element ( 7a ) and the return line ( 6 ) as a function of the coolant temperature T _{coolant, valve} on the element ( 7a ) either with the supply line ( 4 ) or from the supply line ( 4 ), whereas the supply line ( 10 ) by means of valve ( 7 ) from the supply line ( 4 ) is not separable, characterized in that - upstream of the automatically controlling valve ( 7 ) an electrically actuable shut-off element ( 12 ) in the supply line ( 10 ) of the heating cycle ( 9 ) arranged by means of motor control ( 13 ) is controllable in dependence on a temperature T _{coolant of} the coolant. Liquid-cooled internal combustion engine ( 1 ) according to claim 1, characterized in that a sensor ( 14 ) is provided for metrological detection of the coolant temperature T _coolant . Liquid-cooled internal combustion engine ( 1 ) according to claim 2, characterized in that the sensor ( 14 ) for metrological detection of the coolant temperature T _coolant in the coolant circuit ( 3 ) downstream of the at least one cylinder head ( 2 ) and upstream of the heat exchanger ( 8th ) in the coolant circuit ( 3 ) is provided. Liquid-cooled internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that a venting line is provided, which upstream of the shut-off element ( 12 ) into the supply line ( 10 ) and in which a compensating container is arranged. Method for operating an internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the electrically actuable shut-off element ( 12 ) in dependence on a temperature T _{coolant of} the coolant and the load p _{me of} the internal combustion engine ( 1 ), in such a way that the shut-off element ( 12 ) is intermittently opened at the end of the warm-up phase at low and medium loads. Method according to claim 5, characterized in that the shut-off element ( 12 ) after a cold start of the internal combustion engine ( 1 ) is closed in the warm-up phase. Method according to claim 5 or 6, characterized in that the shut-off element ( 12 ) is opened at the end of the warm-up phase, when the instantaneous load p _{me warm} exceeds a predetermined load p _{me, threshold} . Method according to one of claims 5 to 7, characterized in that the electrically actuable shut-off element ( 12 ) as a function of the temperature T _{coolant, circuit of} the coolant in the coolant circuit ( 3 ) and the load p _{me of} the internal combustion engine ( 1 ) is controlled. Method according to one of claims 5 to 8, characterized in that the intermittent opening of the shut-off element ( 12 ) is pulse width modulated at low and medium loads. Method according to one of claims 5 to 8, characterized in that the intermittent opening of the shut-off element ( 12 ) is clocked, wherein a clock comprises a closing phase and an opening phase and having a constant period of time. A method according to claim 10, characterized in that the intermittent opening is performed with a fixed uniform clock, so that the shares of the closing phase and the opening phase of the clock at each clock are the same. A method according to claim 10, characterized in that the intermittent opening is carried out with a variable clock, in which the portions of the closing phase and the opening phase are variable at the clock. A method according to claim 12, characterized in that the proportions of the closing phase and the opening phase are determined on the clock in dependence on the temperature difference .DELTA.T _coolant , by which the instantaneous coolant temperature T _coolant deviates from a predefinable guide value T _{coolant, threshold} . Method according to one of claims 5 to 13, characterized in that the shut-off element ( 12 ) is opened in the warm-up phase, when the current load p _me exceeds a predetermined load p _{me, threshold, cold} .

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