DE10306457B4 - Method and device for increasing the heating power in motor vehicles with internal combustion engines - Google Patents

Abstract

Method for operating an internal combustion engine (10), in which part of an energy that is released when a certain amount of fuel is burned in at least one combustion chamber (14) of the internal combustion engine (10) is absorbed by a cooling medium (48), and in which this part of this energy is varied in a controlled manner by changing operating parameters of the internal combustion engine (10), characterized in that the controlled change in operating parameters causes a dwell time of hot combustion gases in the at least one combustion chamber (14) to be extended to a The duration of a combustion cycle is standardized so that the dwell time is increased by a shift (62) of a combustion center of gravity (58), the shift (62) taking place in such a way that the shifted combustion center of gravity (60) lies in front of a combustion center of gravity (58) in which a the combustion engine's torque resulting from the combustion (10) The maximum is that the displacement (62) of the combustion center (58) takes place in such a way that a pressure curve (68) resulting from combustion rises earlier in the at least one combustion chamber (14) and is flatter overall, and that an outlet valve (20) of the combustion chamber (14) will be opened later.

Description

State of the art

The invention relates to a method for operating an internal combustion engine, wherein a part of an energy that is released when burning a certain amount of fuel in at least one combustion chamber of the internal combustion engine, is absorbed by a cooling medium, and in which this part of this energy by changing operating parameters of the internal combustion engine is varied in a controlled manner.

Furthermore, the invention relates to an apparatus for operating an internal combustion engine according to the above-mentioned method.

Such a method and such a device is in each case from DE 196 44 402 C2 known.

Methods and devices for operating internal combustion engines are usually optimized so that the internal combustion engine operates with the highest possible thermodynamic efficiency. As is known, in internal combustion engines, the chemical energy of the combusted fuel / air mixture is converted in a first approximation into mechanically usable work and waste heat, which is transported away in part with the exhaust gas and is partially absorbed by a cooling medium of the internal combustion engine. As cooling media are known in particular air and water-containing cooling fluids and oil in question.

The heat dissipated by the cooling medium is used by heat exchangers to heat the vehicle. While in previous internal combustion engines about a third of the combustion energy was converted into mechanical work, another third was removed from the exhaust, and the remaining third heated up the cooling medium, modern internal combustion engines achieve higher thermodynamic efficiencies. For example, supercharged diesel engines with direct injection achieve thermodynamic efficiencies of about 45%. Increases in efficiency can also be achieved in gasoline engines through the gasoline direct injection.

With the desired increase in efficiency is inevitably accompanied by a reduction in the amount of heat to be absorbed by the cooling medium. As a result, with a constant dimensioning of the heat exchangers that are used to heat the vehicle, the amount of heat available for heating the vehicle is reduced.

For this reason, in particular motor vehicles which are powered by supercharged direct injection diesel engines are equipped with separate auxiliary heaters. Separate auxiliary heaters, which either burn fuel in their own combustion chamber or which operate electrically, are expensive and, due to their weight, increase their consumption even when not activated.

From the DE 102 60 781 A1 a method for heating an interior of a vehicle is known, in which the exhaust gas recirculation is used via a heat exchanger for interior heating.

From the DE 102 49 541 A1 a cooling and heating circuit for Kreftfahrzeuge is known in which the fuel consumption of the internal combustion engine is artificially increased at high cabin heat demand.

From the EP 1 04 835 A2 An air conditioning system for a motor vehicle is known in which the passenger compartment is heated by the coolant of the internal combustion engine.

From the DE 100 29 231 A1 a device for increasing the heating power in the passenger compartment is known, which causes the engine control unit to carry out measures to increase the engine waste heat.

In the DE 196 44 402 C1 it is stated that the cooling water heat of consumption-optimized internal combustion engines, in particular of direct-injection diesel engines, is often low in the lower load range, so that adequate vehicle heating is no longer possible by utilizing the heat of the cooling medium from the engine cooling circuit via a heating heat exchanger. In addition, the time to reach the operating temperature of the internal combustion engine, which is disadvantageous for the pollutant emissions and, in case of frequent cold starts, for the life of the internal combustion engine.

In the DE 196 44 402 As a remedy, it is suggested to change the control of a diesel injection as a function of the engine operating point if the heat transfer of the cooling medium to the heating heat exchanger is too low. In this case, the change should be made so that the injection is carried out late in the low-load range, with the injection timing used for optimum performance of the internal combustion engine serving as reference time.

Characterized in that the residence time of the hot combustion gas in a combustion chamber of the internal combustion engine by the time period between the beginning of the combustion, the Diesel engine is triggered by the injection, and the opening of the exhaust valve of the internal combustion engine is determined, this measure has a shortening of the residence time of the hot combustion gases in the combustion chamber result.

After DE 196 44 402 As a consequence, the efficiency deteriorates, resulting in the increased generation of heat and increasing the heat input into the cooling medium. On an increased heat dissipation by the exhaust gas is not discussed in this document. That a delayed ignition and / or injection leads to an increase in the exhaust gas temperature is well known. Since the heat dissipated by the exhaust gas is generally not available for heating the vehicle interior, part of the increased heat generated by the efficiency deterioration can not be used in the desired manner for the faster and more intense heating of the cooling medium.

Against this background, the object of the invention is to specify a method and a device for increasing the proportion of the combustion energy that is introduced into the cooling medium. The proportion of heat of combustion, which is removed with the exhaust gas, should be increased as little as possible.

This object is achieved with respect to method aspects by the features of claim 1.

Furthermore, this object is achieved with a device having the features of claim 1.

Advantages of the invention

The inventive method and the device according to the invention have the advantage that the efficiency of the changes made, ie the achieved increase in the heat input based on the resulting deterioration of the thermodynamic efficiency of the internal combustion engine is improved. As a result, only a small amount of additional fuel has to be expended for achieving the desired heating effect. Further, the proposed internal engine measures further advantages over other known solutions that use separate fuel heater, can be achieved.

These advantages result from the fact that the additional fuel requirement used in the context of this invention for heating power increase clean combustion in the internal combustion engine and the resulting exhaust gas is treated without additional lines and guides by an existing exhaust aftertreatment system. Compared to electric auxiliary heaters results in the advantage that generator and battery can be made smaller. It also eliminates efficiency losses caused by the required in electrical heaters conversion of chemical energy into mechanical energy in the engine and the subsequent conversion into electrical energy by the generator.

The residence time is increased by a shift of a combustion center of gravity, wherein the displacement is such that the shifted combustion center is located in front of a combustion center at which a combustion-resultant torque of the internal combustion engine is maximum.

According to the definition customary in engine technology, the center of gravity of the combustion corresponds to that crank angle at which half of the total fuel burning during a power stroke has already been burnt. By advancing the combustion focus, the residence time of the hot combustion gases is extended in the combustion chambers, so that more heat passes through the walls of the combustion chambers in the cooling medium. In addition, by advancing the combustion center of gravity, less mechanical work is gained from the combustion of the combustion chamber charge, so that the combustion chamber charge is to be increased in order to achieve a constant torque. The increase in the combustion chamber filling with reduced efficiency also increases the heat released in the combustion chamber and thus also the heat input into the cooling medium.

The shift of the focal point of combustion takes place in such a way that a pressure curve resulting from combustion increases earlier in the combustion chambers and is generally flatter.

Since a rapidly increasing, high end pressure reaching pressure curve promotes the development of knocking burns, a flatter pressure curve directly counteracts the cause of knocking burns. In addition, the flatter pressure curve results in lower combustion temperatures, which worsens the conditions for the generation of unwanted NOx emissions.

Further, an exhaust valve of the combustion chamber is opened later.

By this measure, which requires a variable valve timing, the residence time of the hot combustion gases is extended in the combustion chamber. In addition, the mechanical efficiency of the internal combustion engine is reduced, since a later opening of the exhaust valve leads to a compression of the hot residual gases, the Internal combustion engine removes mechanical energy. A compensation of this effect by an enlarged combustion chamber filling also contributes to an increased heat transfer into the cooling medium. In addition, can be increased by the late opening of the exhaust valve of the residual gas content of the following combustion chamber filling, which favors a flatter pressure profile and reduces the tendency to knock.

Furthermore, it is preferred that the earlier increase and flatter pressure curve take place by a change in the time profile of injections of fuel into the at least one combustion chamber of the internal combustion engine.

By this measure, especially in diesel engines with direct injection, the combustion process can be shaped in the desired manner.

It is further preferred that an injection of a certain fuel fraction normalized to the injection quantity belonging to a combustion takes place earlier.

The earlier injection, especially in diesel engines, in which combustion is known to be triggered by the injection of fuel into highly compressed air, begins the combustion earlier, which leads to the desired displacement of the combustion center.

The last two aforementioned measures are only applicable to direct injection, while the other measures are also applicable to internal combustion engines with external mixture formation by intake manifold injection or carburetor.

Further, it is preferred that combustion of the particular amount of fuel be triggered earlier.

As a result, the combustion focus can be advanced in the desired manner in gasoline engines by an earlier ignition.

It is preferred that an increase in the exhaust gas recirculation rate takes place in parallel.

The increase in the exhaust gas recirculation rate leads to an increase in the inert gas content at the combustion chamber filling, which releases no energy to increase the pressure during combustion. Therefore, increasing the exhaust gas recirculation rate contributes to reaching the desired flatter pressure curve.

It is further preferred that the movement of fillings or charges of the at least one combustion chamber is reduced.

A high charge movement promotes rapid ignition and burning through the entire cylinder filling. Therefore, slowing down the charge movement contributes to a slower combustion and thus to an intensification of the heat transfer to the cooling medium.

The said preferred embodiments are preferably combined with at least one measure to increase a charge exchange work.

As measures to increase the charge exchange work in particular the following individual measures come into question:
the closing of possibly existing swirl and throttle valves; with variable valve control in connection
with multiple intake ports per cylinder / combustion chamber, keeping an intake port closed; also with variable valve timing, reducing the valve lift; in supercharged internal combustion engines, increasing the boost pressure.

The measures mentioned extract mechanical energy from the internal combustion engine and thus impair its thermodynamic efficiency. The compensation of the efficiency deterioration by an increased combustion chamber filling increases the entry of combustion heat into the cooling system.

In view of the above-mentioned apparatus, it is preferable that the apparatus controls one of the above-mentioned methods and configurations.

Further advantages will become apparent from the description and the accompanying figures.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

drawings

Embodiments of the invention are illustrated in the drawings and grounded in the following description. Show it:

1 schematically an overall view of an internal combustion engine with different, cooperating with the engine components;

2 qualitatively different pressure gradients, as they are in a combustion chamber of the Adjust combustion engine in an embodiment of the invention;

3 qualitatively a shift of a combustion center of gravity;

4 qualitatively different injection curves according to an embodiment of the invention and the prior art;

5 schematically an inlet channel guide with two inlet channels to illustrate intervention possibilities that can be used in the context of an embodiment; and

6 a simplified embodiment of a method according to the invention.

Description of the embodiments

1 shows the overall view of an internal combustion engine 10 in partial section. internal combustion engine 10 has an engine block 12 on, in which at least one combustion chamber 14 through a piston 16 is sealed movable. combustion chamber 14 continues through a cylinder head 17 limited, in which at least one inlet valve 18 and at least one exhaust valve 20 per combustion chamber 14 are guided. intake valve 18 is from an intake valve actuator 22 actuated. outlet valve 20 is through an exhaust valve actuator 24 actuated. Intake valve actuator 22 and exhaust valve actuator 24 can through in the cylinder head 17 be implemented camshafts. Alternatively, pneumatic or electrohydraulic actuators may be used to actuate the intake valves 18 and exhaust valves 20 serve.

With the mentioned valves, the change of the filling of the combustion chamber 14 controlled. When the inlet valve is open 18 sucks the descending piston 16 Gas from the intake manifold 26 at. The amount of air sucked in with a fully variable valve control via a corresponding control of the intake valve actuator 22 to be controlled. Alternatively, the amount of intake air through a throttle 28 in the intake manifold 26 be controlled by a throttle actuator 30 by control commands from a control device 32 to be controlled. Such a control by means of throttling by the inlet valve 18 or through the throttle 28 is typical for a gasoline engine, while diesel engines usually suck unthrottled air.

The control unit 32 be at least signals of an accelerator pedal encoder 33 representing the torque demand by the driver, and a signal about the intake air amount from an air mass meter 34 and a signal about the speed of the internal combustion engine 10 from a speed sensor 36 fed. Based on these signals, the controller controls 32 at least one injection valve 38 per combustion chamber 14 at. In the presentation of the 1 controls the control unit 32 in addition, a spark plug 40 at. It is known that a spark ignition by a spark plug 40 For gasoline engines typical, while diesel engines are known to work with auto-ignition, in which the combustion by injecting fuel into highly compressed air in the combustion chamber 14 is triggered. The presentation of the 1 Therefore, extends to both diesel engines and gasoline engines, in diesel engines, the spark plug 40 does not need to be present.

After combustion, the residual gases through the open exhaust valve 22 in an exhaust pipe 42 directed, with the expulsion of the burned gases from the combustion chamber 14 through the ascending piston 16 is supported. About a connection 44 between exhaust pipe 42 and suction pipe 26 can exhaust gas to the intake side of the engine 10 to be led back. In this case, the amount of recirculated gas from the controller 32 by controlling an exhaust gas recirculation valve 46 controlled. While a part of the combustion chamber 14 released energy the piston 16 drives down and thus performs mechanical work, another part of the energy released in the form of heat through the exhaust pipe 42 dissipated.

The remainder of the energy released during combustion is transmitted through the walls of the engine block 12 and the cylinder head 17 a cooling medium 48 supplied in the internal combustion engine 10 circulated by a pump. The cooling medium 48 , usually a water-based liquid mixture, is generally passed through a cooler, not shown, in which it is cooled by the wind. For heating a vehicle interior, which is in the 1 not shown, a heat exchanger is used 54 that's over wires 50 and 52 with the in the combustion engine 10 circulating cooling medium 48 connected is. That through the heat exchanger 54 flowing cooling medium 48 gives off a part of its heat to an air stream, which is the heat exchanger 54 flows through and in the 1 through an arrow 56 is presented. The heated air flow is passed through lines not shown in the vehicle interior and heats the vehicle interior.

According to the invention, the residence time of the hot combustion gas in the combustion chamber 14 extended when the control unit 32 detects an increased heating power requirement. The residence time of the hot combustion gas in the combustion chamber 14 is by the time period between the initiation of the combustion of the combustion chamber filling and the opening of the exhaust valve 20 Are defined. According to the invention, this residence time is by advancing the time at which the combustion is triggered, and / or by a delay of the time at which the exhaust valve 20 opens, extends.

In the 2 represents the pressure curve 64 a pressure curve in the combustion chamber 14 how he sets himself without triggering a burn. This results in the maximum pressure in the pressure curve 64 in the area of top dead center OT of the piston 16 through the piston 16 at the in the combustion chamber 14 enclosed combustion chamber filling performed compression work. The pressure curve 66 shows in comparison to an excessive maximum, which is due to combustion of the combustion chamber filling of the combustion chamber 14 is triggered. In this case, the combustion chamber filling in the normal case, ie if there is no increased heating power requirement, by a triggered at time t1 and the reference numeral 70 designated ignition triggered. In this case, the ignition time t1 is predetermined so that the maximum of the pressure rise of the pressure curve 66 after passing through top dead center. To be precise, the time t1 is generally predetermined to be from the pressure history 66 above the piston 16 resulting, on a crank mechanism of the internal combustion engine 10 transmitted torque is maximum.

According to the invention, when the control unit 32 indicates an increased heating power requirement, the combustion is triggered at an earlier time t2, resulting in the 2 by the reference numeral 72 is represented. This causes the pressure increase earlier. To an undesirably rapid increase in pressure after the advanced ignition 72 To avoid, for example, the Inertgasanteil the combustion chamber filling the combustion chamber 14 by opening the exhaust gas recirculation valve 46 be increased before sucking the combustion chamber filling.

Ideally, a pressure gradient sets in, as he in the 2 through the numeral 68 is represented. This pressure curve is characterized in that it compared to the pressure curve of the regular combustion 66 rises earlier, is wider overall and flatter. This not only the residence time of the hot combustion gases in the combustion chamber 14 increased, but it may additionally the mechanical efficiency of the engine 10 be reduced. This reduction results from being part of the pressure curve 68 even before passing through the top dead center OT strong against the pressure curve 64 is increased. As a result, the still on top dead center TDC piston is approaching 16 braked by the onset of combustion incipient increase in pressure.

The loss of mechanical power due to this is provided by the controller 32 via a control of the throttle valve 28 and / or the intake valve actuator 22 balanced by the combustion chamber filling is increased. As a result, in a combustion according to the pressure curve 68 burned a larger combustion chamber filling than in a regular combustion according to the pressure curve 66 when the same torque is generated in both cases. As a result, in the case of the pressure waveform 68 the total in the combustion chamber 14 released amount of heat and thus in the cooling medium 48 transferred amount of heat increased as needed.

The numeral 74 in the 2 indicates the regular opening time of the exhaust valve 20 , which is usually in the range of 40 to 90 degrees before bottom dead center UT. To extend the residence time of the hot combustion phase in the combustion chamber, this point in time can be moved to the rear with a variable valve control. The numeral 76 in the 2 represents such a shifted opening timing of the exhaust valve 20 and the arrow 78 additionally illustrates the direction of such a shift.

The presentation of the 2 applies to both a gasoline engine and a diesel engine. In a gasoline engine correspond to the triggers 70 . 72 of burns respectively the times at which the control unit 32 via a high voltage generating circuit, not shown for reasons of clarity, the spark plug 40 controls. In the case of a diesel engine comply with 70 . 72 each time designated the beginning of an injection of fuel in the high-density filling of the combustion chamber 14 with air.

3 illustrates how a combustion focus 58 , which leads to a regular combustion and thus to the pressure curve 66 in the 2 corresponds, is moved. The regular focus of combustion 58 lies, as in 3 shown after the top dead center OT. By the shift 62 becomes the focal point of combustion 60 in a position 60 moved closer to OT. As already mentioned above, the focus of combustion corresponds to the point in time at which half of the quantity of fuel to be burned during combustion has already been burnt.

4 shows different injection curves over time. The numeral 80 in the 4 denotes the envelope of an injection divided into three sub-injections. It corresponds with the 82 designated curve of a pilot injection, with 84 designated curve corresponds to a main injection and with 86 designated curve corresponds to a post-injection. The one by the envelope 80 or through the curves 82 . 84 and 86 defined injection corresponds to a regular combustion. The numeral 87 in the 2 On the other hand, it shows a changed course of injection, which starts earlier and ends later.

Due to the earlier insertion and later ends, the period in which heat is in the combustion chamber 14 is released, extended. It corresponds to the number 87 drawn injection course to some extent the envelope 86 of single injections 82 . 84 and 86 , Accordingly, the injection course 87 be constructed of several individual injections, by the envelope 87 be enclosed. Of course, the distribution of the injection quantity is not limited to the division shown in three partial injections. Instead, one, two, or any other number of split injections may be used. The modification of the course of injection shown is particularly relevant in diesel engines, in which the injection triggers the combustion. However, the modification shown is not limited to the application in diesel engines. This modification can also be used in gasoline engines with direct injection, even if the combustion there by the activation of a spark plug 40 is triggered.

5 shows a possibility, as with gasoline engines with äßerer mixture formation, ie when mixture in the intake manifold 26 by intake manifold injection or by a carburetor, which can be influenced combustion. In the presentation of the 5 are two inlet channels 88 and 90 represented by the air from the intake manifold 26 in the assigned combustion chamber 14 flows. One of the two inlet channels, in the representation of the 5 the inlet channel with the numeral 90 , has a so-called swirl flap 92 on, from the control unit 32 via a swirl flap plate 94 can be operated. Depending on the position of the swirl flap 92 the gas flows out of the intake manifold 26 with different swirl in the combustion chamber 24 ,

At a symmetrical to the center of the combustion chamber 14 both flows in the combustion chamber meet in parallel via both inlet channels 14 together, which compensates for their respective twist. In contrast, with closed swirl flap 92 Gas from the intake manifold 26 at increased speed through the remaining inlet duct 88 off-center in the combustion chamber 14 inflow, which leads to a strong turbulence and a strong twist of the combustion chamber filling. According to the invention, in such circumstances, as an alternative and / or in addition to the measures described above, the swirl flap 92 open so that the movement of the combustion chamber filling in the combustion chamber 14 reduced. Due to the reduced movement of the combustion chamber filling, the flame front also moves in the combustion chamber 14 progressing slower after triggering a combustion. As a result, the heat release in the combustion chamber 14 extended in time, which ultimately leads to increased heat input into the cooling medium 48 of the internal combustion engine 10 contributes.

6 shows an embodiment of the method according to the invention. step 96 represents an engine control program in which the internal combustion engine 10 is controlled so that the maximum possible torque and maximum efficiency possible sets. In other words, step 96 corresponds to a control of the internal combustion engine 10 in which pressure curve curves corresponding to the pressure curve 66 in the 2 to adjust. In step 98 It is checked whether there is an increased heating power requirement. An increased Heizleistungsbedarf can in particular at low combustion chamber fillings and after a cold start of the engine 10 consist. In this case, the method according to the invention branches to a step 100 in which the internal combustion engine 10 operated with changed operating parameters. The change in the operating parameters is such that the heat input into the cooling medium 48 of the internal combustion engine 10 is increased.

For this, all the measures described above come into question. Starting from the step 100 is in the step 102 checks whether the increased heating power requirement still exists. If yes, the program branches again to the step 100 so that the engine continues to operate so that the heating power is increased. In other words, this operation corresponds to an engine operation in which pressure curve curves corresponding to the pressure curve 68 in 2 to adjust. Will the query in step 102 in contrast, the program branches back into the step 96 , in which the engine is operated normally again. Analog also becomes out of step 98 back into the normal control program of the step 96 branches when in step 98 no increased heating power requirement is detected.

Claims (9)

Method for operating an internal combustion engine ( 10 ), in which a part of an energy that is generated when a certain quantity of fuel is burned in at least one combustion chamber ( 14 ) of the internal combustion engine ( 10 ) is released from a cooling medium ( 48 ) and in which this part of this energy is changed by changing the operating parameters of the internal combustion engine ( 10 ) is varied in a controlled manner, characterized in that the controlled change of operating parameters extends the residence time of hot combustion gases in the at least one combustion chamber ( 14 ) normalized to a period of a combustion cycle, that the residence time is determined by a displacement ( 62 ) of a combustion center ( 58 ), the displacement ( 62 ) is carried out so that the shifted focus of combustion ( 60 ) before a combustion focus ( 58 ), in which a resulting from the combustion torque of the internal combustion engine ( 10 ) maximum is that the displacement ( 62 ) of the combustion center ( 58 ) is carried out so that a combustion process resulting from burns ( 68 ) in the at least one combustion chamber ( 14 ) rises earlier and is generally flatter, and that an exhaust valve ( 20 ) of the combustion chamber ( 14 ) opens later. Method according to claim 1, characterized in that the earlier rise and flatter pressure course ( 68 ) by a change in the time profile of injections of fuel into the at least one combustion chamber ( 14 ) of the internal combustion engine ( 10 ) he follows. A method according to claim 2, characterized in that an injection of a certain proportion of fuel, which is normalized to the injection quantity associated with a combustion takes place earlier. Method according to one of claims 1 to 3, characterized in that a combustion of the determined amount of fuel is triggered earlier. Method according to one of claims 1 to 4, characterized by a parallel increase in the exhaust gas recirculation rate. Method according to claim 1, characterized in that the movement of charges of the at least one combustion chamber ( 14 ) is reduced. Method according to at least one of claims 1 to 6, characterized in that it is combined with at least one measure to increase a charge exchange work. Contraption ( 32 ) for operating an internal combustion engine ( 10 ), in which a part of an energy that is generated when a certain quantity of fuel is burned in at least one combustion chamber ( 14 ) of the internal combustion engine ( 10 ) is released from a cooling medium ( 48 ), the device ( 32 ) this part of this energy by changing operating parameters of the internal combustion engine ( 10 ) Varies in a controlled manner, characterized in that the device ( 32 ) changes the operating parameters such that a residence time of hot combustion gases in the at least one combustion chamber ( 14 ), normalized to a period of a combustion cycle, lengthens the residence time by a displacement ( 62 ) of a combustion center ( 58 ), the displacement ( 62 ) is carried out so that the shifted focus of combustion ( 60 ) before a combustion focus ( 58 ), in which a resulting from the combustion torque of the internal combustion engine ( 10 ) is maximum, and that the displacement ( 62 ) of the combustion center ( 58 ) is carried out so that a combustion process resulting from burns ( 68 ) in the at least one combustion chamber ( 14 ) rises earlier and is generally flatter, and that the device is an exhaust valve ( 20 ) of the combustion chamber ( 14 ) opens later. Contraption ( 32 ) according to claim 8, characterized in that the device ( 32 ) controls at least one of the methods according to claims 2 to 7.

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