DE102016216116A1 - Method and device for operating an internal combustion engine in overrun mode - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine having at least one cylinder with a variable adjustment of Maximalhub and spread Ventilhubverläufen at least one intake valve and at least one exhaust valve, wherein the Ventilhubverläufe the intake valve and the exhaust valve are set in overrun operation of the internal combustion engine so that no flow the cylinder is done with fresh air and / or completely cancel each other compression work during a compression stroke and relaxation work during a relaxation cycle.

Description

Technical area

The invention relates to internal combustion engines, in particular operating phases of internal combustion engines, in which the internal combustion engine without fuel injection by the inertia of the thus operated motor vehicle is towed in a coasting operation. Furthermore, the present invention relates to measures for reducing the drag torque of a combustion engine operated in overrun mode.

Technical background

Internal combustion engines in motor vehicles are usually connected via the drive train directly to the driving wheels. In the case of deceleration, the internal combustion engine is entrained via the closed drive train by the inertia of the motor vehicle, wherein the motor vehicle is decelerated by a drag torque exerted by the internal combustion engine. The operating mode of the internal combustion engine, in which the internal combustion engine is towed without injecting fuel into the cylinders, is called overrun operation.

During overrun operation, the filling of the internal combustion engine is provided with fresh air as low as possible or chosen so that when leaving the overrun operation as quickly and conveniently a desired drive torque can be provided. To adjust the filling, the air mass flow supplied to the internal combustion engine is generally controlled via a position of the throttle valve and / or a control of the inlet valve.

Generally, variable valve trains for the intake and exhaust valves are known which make it possible to variably set the intake valve lift and the intake valve spread as well as the exhaust valve lift and the exhaust valve spread.

From the publication DE 199 32 665 A1 a method for controlling gas exchange valves of an internal combustion engine in a variable valve timing is known, wherein the intake valves are driven variably in the shift operation. Also the publication WO 2006/037422 A1 describes a variable valve train for an internal combustion engine.

The drag torque of the internal combustion engine is essentially caused by friction and charge exchange losses. However, in hybrid drive systems in particular, it may be desirable to reduce the drag torque of the internal combustion engine as much as possible in order to use the torque resulting from the moment of inertia provided by the drive train for recuperation of electrical energy during overrun with the powertrain closed. In such a case, it is desirable that the drag torque of the non-active internal combustion engine is minimized.

So far, while the throttle valve can be substantially opened in overrun, but continue to losses due to the flow of the cylinder with fresh air, charge cycle losses and compression losses when Entrainment of the internal combustion engine available.

It is an object of the present invention to provide a method for reducing a drag torque in overrun operation of an internal combustion engine, whereby in particular the drag torque can be significantly reduced.

Disclosure of the invention

This object is achieved by the method for operating an internal combustion engine according to claim 1 and by an apparatus and an engine system according to the independent claims.

Further embodiments are specified in the dependent claims.

According to a first aspect, a method for operating an internal combustion engine with a variable adjustment of Maximalhub and spread the Ventilhubverlaufs at least one intake valve and at least one exhaust valve is provided, the Ventilhubverläufe the intake valve and the exhaust valve are set in the overrun mode of the engine so that no flow through the Cylinder with fresh air takes place.

One idea of the above method is to ensure that as little fresh air as possible is moved in overrun by the cylinder of the internal combustion engine and at the same time to provide during a compression stroke and a relaxation stroke that the compression work required to compress the fresh air in the cylinder substantially the relaxation work in a corresponds to the following relaxation cycle, which corresponds to a combustion cycle during combustion. As a result, both the charge exchange work and the flow losses or compression losses can be reduced.

Further, the valve opening timing of the intake valve and the exhaust valve may be arranged symmetrically about the top dead center between an exhaust stroke and an intake stroke. That is, the timing of closing the Inlet valve with respect to the bottom dead center of the piston movement in the cylinder before the compression stroke and the timing of opening the exhaust valve are preferably symmetrical with respect to the bottom dead center of the piston movement between the combustion / expansion stroke and exhaust stroke.

It can be provided that the control times of the maximum valve lift of the exhaust valve are between 0 ° CA and -180 ° CA, in particular at 0 ° CA, -60 ° CA, -180 ° CA or between -130 ° CA and -170 ° CA , lie and / or the times of the maximum valve lift of the intake valve are between 0 ° CA and 180 ° CA, in particular at 0 ° CA, + 60 ° CA, + 180 ° CA or between + 130 ° CA and + 170 ° CA ,

Furthermore, the maximum valve lifts of the intake valve and the exhaust valve may be identical.

According to one embodiment, the compression work to be performed during a compression stroke may correspond to the relaxation work released during a subsequent expansion stroke.

Alternatively, the maximum valve lift of the intake valve and the exhaust valve may be different, wherein the maximum lift and the closing timing of the intake valve during an intake stroke and the maximum stroke and the opening timing of the exhaust valve during a decompression stroke are selected so that in the existing filling in the combustion chamber of the cylinder required compression work of the released relaxation work corresponds.

Furthermore, the maximum valve lifts of the intake valve and the exhaust valve may be different, with the valve opening durations of the intake valve and the exhaust valve overlapping and a resulting total opening duration corresponding to a crankshaft angle range of between 300 ° CA and 420 ° CA, in particular 360 ° CA (effective).

It can be provided that only the inlet valve or the outlet valve is opened, while the other valve remains closed over all working cycles.

Brief description of the drawings

Embodiments are explained below with reference to the accompanying drawings. Show it:

1 a schematic representation of a cylinder of an internal combustion engine;

2 an illustration of the working stroke in the operation of the internal combustion engine in four-stroke operation, wherein the cylinder strokes of the intake and exhaust valves are shown for the conventional operation of an internal combustion engine;

3 a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four power strokes of an internal combustion engine at a first valve control

4 a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four work cycles of an internal combustion engine in a further valve control;

5 a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four work cycles of an internal combustion engine in a further valve control;

6 a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four work cycles of an internal combustion engine in a further valve control;

7 a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four work cycles of an internal combustion engine in a further valve control;

8th a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four work cycles of an internal combustion engine in a further valve control; and

9 a schematic representation of the valve lifts and spreads over the crankshaft angle of a cycle of four power strokes of an internal combustion engine in a further valve control.

Description of embodiments

1 schematically shows a cross-sectional view through a cylinder 2 an internal combustion engine 1 , The internal combustion engine 1 can have any number of typically identical cylinders, each operated in a four-stroke operation.

Each of the cylinders 2 has a movable piston 3 up, over a connecting rod 4 with a crankshaft 5 is coupled, so that one translational movement of the piston 3 in the combustion mode in the cylinder 2 in a rotational movement of the crankshaft 5 is implemented and a position of the piston 3 in the cylinder 2 a crankshaft angle of the crankshaft 5 equivalent. In overrun mode, ie the internal combustion engine 1 is dragged by concerns an external moment, is correspondingly a rotational movement of the crankshaft 5 in a translatory movement of the piston 3 in the cylinder 2 implemented.

By the movement of the piston 3 becomes a combustion chamber 6 in the cylinder 2 enlarged and reduced.

The internal combustion engine 1 is operated in combustion operation in a four-stroke operation with four power strokes, wherein a compression stroke KT, a combustion stroke VT corresponding to a relaxation stroke in a coasting operation, an exhaust stroke AT and an intake stroke ST are performed in this order. The indication of the crankshaft angle is associated with the power strokes so that 0 ° CA corresponds to a top dead center of the crankshaft movement between the Austoßtakt AT and the intake stroke ST.

For supplying fresh air is a fresh air supply system 12 provided that via at least one inlet valve 7 Fresh air to the combustion chamber 6 of the cylinder 2 can supply. In the fresh air supply system 12 can a throttle 14 be provided for controlling the supplied air mass flow. Furthermore, for the removal of combustion exhaust gases, an exhaust gas removal system 13 provided that via at least one exhaust valve 8th Combustion gases from the combustion chamber 6 of the cylinder 2 can emit.

The fuel can go directly into the combustion chamber 6 of the cylinder 2 with the help of an injection valve 9 be injected.

The crankshaft 5 is coupled to two camshafts (not shown) that control valve lift of the intake valve 7 and the exhaust valve 8th Taxes. Through an inlet valve adjustment 10 may be the maximum lift of Ventilhubverlaufs the intake valve 7 and its spread can be varied. Accordingly, with the aid of an outlet valve adjustment 11 the maximum stroke of the Ventilhubverlaufs the exhaust valve 8th and its valve spread can be adjusted. The spread of a valve corresponds to the time duration between a maximum opening of the respective valve to the top dead center OT of the crankshaft movement between the Ausstoßtakt AT and the intake stroke ST.

In 2 is a course of the valve lifts the intake valve and the exhaust valve 7 . 8th above the crankshaft angle ° CA of the crankshaft 5 shown in a conventional valve control. The crankshaft angle for a working cycle corresponds to 720 ° and ranges from -360 ° to + 360 ° in the diagram shown. Regarding the power strokes of the internal combustion engine 1 Corresponds to the crankshaft angle range of -360 ° to -180 ° a combustion cycle VT, which corresponds to a relaxation cycle in overrun. The crankshaft angle range of -180 ° to 0 ° C corresponds to an exhaust stroke AT, in which combustion exhaust gases are discharged into the exhaust tract in the combustion operation. The power stroke between the crankshaft angle 0 ° and 180 ° corresponds to the intake stroke ST, in the fresh air from the fresh air supply system 12 in the combustion chamber 6 of the cylinder 2 is sucked, and a subsequent compression stroke KT is used to compress the gas filling in the combustion chamber 6 of the cylinder 2 ,

The crankshaft angles -360 ° and 360 ° correspond to the same position of the piston 3 at a top dead center OT correspond to the piston movement between a compression stroke KT and a combustion stroke / relaxation stroke VT. Another top dead center is located at 0 ° crankshaft angle between an exhaust stroke AT and an intake stroke ST. Bottom dead centers UT are at -180 ° between the combustion stroke / relaxation stroke VT and the exhaust stroke and 180 ° between the intake stroke ST and the compression stroke KT.

In overrun operation eliminates the combustion cycle, since no fuel injected and no ignition is performed and there is a relaxation cycle instead, in which the gas filling in the cylinder 2 is relaxed. With unchanged valve train of the intake valve 7 and the exhaust valve 8th However, in overrun a fresh air through the cylinder 2 pumped, whereby usually hired throttle valve flow losses in the cylinder 2 and arise in the air supply system, resulting in a significant drag torque of the internal combustion engine 2 being able to lead.

To the drag torque of the internal combustion engine 2 to reduce, in particular, if the energy provided by the inertia of the motor vehicle energy is to be converted as possible generator into electrical energy, and drag losses in the internal combustion engine 2 be kept as low as possible, is provided by a suitable adjustment of the valve trains, the flow losses and the compression losses and the charge exchange losses in the cylinders 2 to reduce.

In 3 are the valve lift curves of the intake and exhaust valves 7 . 8th shown in which the opening periods of the inlet and Exhaust valve overlap. The control of the intake and exhaust valve is carried out with the throttle fully open 14 in the air supply system 12 , so that the flow losses at the throttle 14 are also reduced. The time of opening the exhaust valve AÖ is preferably between -330 ° and -180 ° CA, in particular at -180 ° CA, and the time of closing of the intake valve ES between 180 ° and 330 ° CA, in particular at 180 ° KW. The valve lift curves show a symmetrical arrangement around the top dead center OT at 0 ° crankshaft angle, wherein the timing of opening the intake valve between -30 ° KW and -90 ° KW and the time of closing the exhaust valve between 30 ° CA and 90 ° CA. The closing of the inlet valve at about 180 ° kW and the opening of the outlet angle at about -180 ° CA causes the compression stroke and the relaxation stroke VT compression work and relaxation work are the same, compensate and thus not increased Contribute drag torque. Due to the large opening cross-sections of the intake valve and exhaust valve, the flow losses are at the same time open throttle valve almost zero. As a result, the charge exchange losses are low and the air flow rate is maximum.

In 4 the valve lift curves are also arranged symmetrically to top dead center OT at 0 ° kW, wherein the maximum opening stroke of the intake and exhaust valves 7 . 8th are each provided at bottom dead centers UT at 180 ° KW and -180 ° KW. The opening time ranges of the exhaust valve 8th and the intake valve 7 do not overlap, but is in every stroke of the engine 2 at least one of the valves 7 . 8th opened for at least 70 ° to 110 ° KW, in the illustrated internal combustion engine 1 even for at least 120 ° crankshaft angle.

5 shows a similar control of the intake valves 7 and exhaust valves 8th , where the maximum stroke is between -120 and -180 ° KW or 120 and 180 ° kW. Time AST of closing the exhaust valve 8th and the time point EÖT of opening the intake valve 7 is about the top dead center at 0 ° CA, preferably between -30 ° CA and 30 ° CA.

In the embodiment of the 6 become the inlet valve 7 and the exhaust valve 8th driven substantially synchronously, wherein the maximum valve opening is provided at top dead center at 0 ° KW. The opening EWT / AÖT and closing times EST / AST of the inlet and outlet valves 7 . 8th are also identical, so that the compression KT and relaxation work VT are the same. By simultaneously opening the inlet 7 and exhaust valves 8th there is no flow through the cylinder 2 with fresh air, so that the flow losses and charge exchange losses are also minimal.

In 7 a maximum opening duration of the valve lift curve for the outlet valve of between 210 to 300 ° CA, so that even during the relaxation cycle VT an opening to Abgasabführungssystem 13 he follows. Through a reduced valve lift when opening the inlet valve 7 at about 0 ° CA at top dead center OT, only a small amount of air is drawn in from the air supply system 12 , Due to the early timing of closing the intake valve 7 Thus, the amount of air that is sucked during an intake stroke ST, low. As a result, a small amount of fresh air must be compressed during the compression stroke KT. Opening the exhaust valve 8th during the relaxation cycle VT is chosen so that the counteracting relaxation work is identical, so that the drag torque is reduced accordingly. The overlap between the Auslaßventilöffnungszeitdauer and the intake valve opening period results in a total opening period, which is preferably in the range of 300 to 420 ° KW, in particular of 360 ° KW, to choose.

The total opening time can be adjusted depending on the speed, so that taking into account the flow dynamics, the effective opening duration of 360 ° kW can be maintained. Lower fill may be due to an earlier exhaust spread in combination with smaller valve lift of the intake valve 7 and smaller inlet spread. A higher charge can be represented by a later exhaust spread and larger intake valve lift as well as larger intake spreads.

Furthermore, a drag torque can be reduced by only the exhaust valve 8th is controlled with an outlet spread of between -150 to -40 ° KW or, as in 9 shown, an exclusive control of the intake valve with an intake valve spread between 40 ° to 150 ° CA at low valve lift (about 5-30% of the maximum stroke) of the intake valve 7 ,

In a further variant, both the inlet valve 7 as well as the exhaust valve 8th deactivated, wherein the deactivation takes place such that at the end of an exhaust stroke AT the exhaust valve 8th is closed so that this remains closed in the subsequent cycles. This is analogous to the intake valve 7 performed, following the intake stroke ST at about 180 ° KW. The shutdown sequence is initially the shutdown of the exhaust valve 8th and then switching off the intake valve 7 ,

The filling can additionally by throttling the supplied fresh air mass flow through the throttle 14 or a reduced intake valve lift can be set low, so that in the cylinder 2 the desired cylinder charge can be included to restart the fired operation. The shutdown can also be done in pairs of cylinders, ie the common shutdown of the valve train of the exhaust valves 8th for several cylinders 2 ,

In an alternative embodiment, the intake and exhaust valves 7 8th remain permanently open, so that the pumping losses are reduced by providing appropriate valve cross-sections.

LIST OF REFERENCE NUMBERS

1

internal combustion engine

2

cylinder

3

piston

4

pleuel

5

crankshaft

6

combustion chamber

7

intake valve

8th

outlet valve

9

Injector

10

Intake valve adjustment

11

Auslassventilverstellung

12

Fresh air supply system

13

Flue gas discharge system

14

throttle

KT

compression stroke

VT

relaxation clock

AT

exhaust stroke

ST

intake

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 19932665 A1 [0005]
• WO 2006/037422 A1 [0005]

Claims (10)

Method for operating an internal combustion engine ( 1 ) with at least one cylinder ( 2 ) with a variable adjustment of Maximalhub and spread of Ventilhubverläufen least one inlet valve ( 7 ) and at least one exhaust valve ( 8th ), wherein the valve lift characteristics of the intake valve ( 7 ) and the exhaust valve ( 8th ) in overrun operation of the internal combustion engine ( 1 ) are adjusted so that no flow through the cylinder ( 2 ) is done with fresh air and / or completely cancel each other compression work during a compression stroke (KT) and relaxation work during a relaxation cycle (VT). Method according to claim 1, wherein the valve opening times of the inlet valve ( 7 ) and the exhaust valve ( 8th ) are arranged symmetrically about the top dead center between an exhaust stroke (AT) and an intake stroke (ST). Method according to claim 1 or 2, wherein the times of the maximum valve lift of the exhaust valve ( 8th ) are between 0 ° CA and -180 ° CA, in particular at 0 ° CA, -60 ° CA, -180 ° CA or between -130 ° CA and -170 ° CA, and / or the times of the maximum valve lift of the intake valve ( 7 ) are between 0 ° CA and 180 ° CA, in particular at 0 ° CA, + 60 ° CA, + 180 ° CA or between + 130 ° CA and + 170 ° CA. Method according to one of claims 1 to 3, wherein the maximum valve lifts and / or the opening times of the intake valve ( 7 ) and the exhaust valve ( 8th ) are identical.  Method according to one of claims 1 to 4, wherein the compression work to be performed during the compression stroke (KT) corresponds to the expansion work released during the subsequent expansion stroke (VT). Method according to one of claims 1 to 3, wherein the maximum valve lift of the intake valve ( 7 ) and the exhaust valve ( 8th ), wherein the maximum lift and the closing time of the intake valve ( 7 ) during the compression stroke (KT) and the maximum stroke and the opening time of the exhaust valve (FIG. 8th ) are selected during the relaxation cycle (VT) so that in the existing filling in the combustion chamber of the cylinder ( 2 ) The required compression work of the released relaxation work corresponds. Method according to one of claims 1 to 3, wherein the maximum valve lift of the intake valve and the exhaust valve ( 8th ) are different, wherein the valve opening periods of the intake valve ( 7 ) and the exhaust valve ( 8th ) overlap and a resulting total opening duration corresponds to a crankshaft angle range of between 300 ° CA and 420 ° CA, in particular 360 ° CA. Method according to one of claims 1 to 3, wherein only the exhaust valve is driven in the overrun mode with an outlet spread of between -150 to -40 ° CA, while the inlet valve ( 7 ) remains closed over all working cycles, or only the inlet valve ( 7 ) is controlled with an intake valve spread between 40 ° to 150 ° CA, wherein in particular the valve lift only between 5% and 30% of the maximum lift of the intake valve ( 7 ), while the exhaust valve ( 8th ) remains closed over all working cycles. Method according to one of claims 1 to 3, wherein the inlet valve ( 7 ) and the exhaust valve ( 8th ) are opened permanently in overrun mode. Device for operating an internal combustion engine ( 1 ) with a variable adjustment of maximum lift and spread of the valve lift characteristics of at least one intake valve ( 7 ) and at least one exhaust valve ( 8th ), wherein the device is designed to control the valve lift characteristics of the intake valve ( 7 ) and the exhaust valve ( 8th ) in overrun operation of the internal combustion engine ( 1 ) so that no flow through the cylinder ( 2 ) is done with fresh air and / or completely cancel each other compression work during a compression stroke (KT) and relaxation work during a relaxation cycle (VT).

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