DE102016011334A1 - Method for operating a coolant injection device - Google Patents

Abstract

The invention relates to a method for operating a coolant injection device (20) for an internal combustion engine (1), in which by a control unit, a release of a coolant injection in a combustion chamber of the internal combustion engine (1) is granted (S7) to start the coolant injection, and at which is denied the release to inhibit the coolant injection, the release is issued (S7), when a temperature limit of at least one of the internal combustion engine (1) relevant operating medium temperature (S3, S4, S5) is reached.

Description

The invention relates to a method for operating a coolant injection device for an internal combustion engine, in which by a control unit, a release of a coolant injection is issued in a combustion chamber of the internal combustion engine to start the coolant injection, and in which the release is denied to prevent the coolant injection.

Due to an unbroken trend of downsizing to reduce CO ₂ emissions in combustion engine-powered cars, both the specific torque and the specific power of internal combustion engines continue to increase. This is made possible, for example, by charging a combustion engine equipped with a direct injection system, wherein the charging can take place for example by means of an exhaust gas turbocharger. In order to be able to achieve a favorable efficiency - and thus a low fuel consumption - in turbocharged operation, an internal combustion engine should be operated with a favorable combustion centroid. For this purpose, an effective cooling of compressed air, which can also be referred to as so-called intercooling, of particular importance. The intercooler gains - due to the pursuit of increasing the compression ratio with the aim of further improving fuel consumption - increasingly important. In addition, a representable, maximum torque, especially at higher engine speed, limited due to component-specific limit temperatures. This results in a need for additional cooling measures, especially when a combustion centroid point is to be shifted "toward early". For example, if the combustion focus is at 17 ° crank angle after the top (piston) dead center (17 ° CA after TDC), a shift of the combustion center point "toward early" would correspond, for example, to a center of gravity of 12 ° CA after TDC.

Both with increasing specific torque and increasing specific power of the internal combustion engine, as well as by increasing the compression ratio, the cooling demand of the compressed air and additionally or alternatively the combustion chamber continues to increase.

In current gasoline engines intercooling takes place, for example, by means of a charge air cooler, which is flowed through by the compressed air and this thus withdraws heat. The latter is then discharged from a heat exchanger directly to the environment or to a cooling medium flowing through the heat exchanger of a low-temperature circuit. Here, a distinction is made between a so-called direct charge air cooling and an indirect charge air cooling.

Exceeding component-specific limit temperatures at high loads is prevented today by an enrichment of an air-fuel mixture or by a reduction of a maximum available torque. The additionally injected for cooling purposes fuel leads due to a lack of oxygen to increased pollutant emissions (due to a so-called substoichiometric combustion), which in particular by future exhaust gas legislation (real-driving emissions) is to be considered critical. One alternative known today is the use of higher-grade materials or the use of optimized cooling devices on the so-called "hot side" of the internal combustion engine. The "hot side" corresponds to a region flooded with hot exhaust gas, which comprises, for example, an exhaust manifold and an exhaust gas turbocharger turbine housing. Such cooling devices can be used, for example, for cooling the exhaust manifold and additionally or alternatively, for example, the exhaust gas turbocharger turbine housing.

Another very effective way to cool combustion air and to lower process temperature is an injection of a cooling medium in the compressed combustion air. This combustion heat is removed due to the high specific heat capacity of the cooling medium and its evaporation (phase change). In addition to reducing the risk of knocking combustion, this can react to or prevent any pre-ignition, as can be seen for example from the document DE 10 2012 207 904 A1 is known. To suppress a tendency to knock and Vorentflammungsneigung this can be achieved with a high pressure introduced cooling medium wall wetting for cooling the combustion chamber walls.

From the publication DE 10 2014 204 509 A1 a water injection system with a water tank and with a arranged in the water tank heater is known. In this case, an injection of water by means of the local water injection system already takes place during a cold start of the local internal combustion engine in order to heat up a catalyst of the internal combustion engine even faster in an engine warm-up than would be the case without water injection.

Object of the present invention is a method of the type mentioned to provide, by means of which a coolant injection is performed particularly gentle on the engine.

This object is achieved by a method having the features of patent claim 1. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the remaining claims.

The invention is based on a method for operating a coolant injection device for an internal combustion engine. In this case, a release of a coolant injection in a combustion chamber of the internal combustion engine is granted by a control unit to start the coolant injection and denied the release to prevent the coolant injection.

In order to perform a coolant injection particularly gentle on the engine for an internal combustion engine, it is provided according to the invention that the release is granted when a temperature limit of at least one operating medium temperature which relates to the internal combustion engine is reached. This is advantageous, since such a temperature limit represents a particularly meaningful indicator for a possible achievement of component-specific limit temperatures of the internal combustion engine. Since the release is only issued when the temperature limit of the at least one operating medium temperature is reached, a particularly motor-friendly dosing of the coolant injection can be done and thereby an excessive entry of the coolant, which can also be referred to as a cooling medium, be avoided in the engine oil of the internal combustion engine. Thus, for example, a wall wetting of respective combustion chamber walls of cylinders of the internal combustion engine can be limited at least to a particularly low level and an unfavorable for any engine oil change intervals Motorölverdünnung be reduced by the entry of coolant at least greatly.

Unlike systems known from the prior art, it can be ensured by the method according to the invention that the release is only issued when the internal combustion engine is at operating temperature, accordingly has already warmed up and thus is no longer operated under cold start conditions. For example, the operating medium temperature may correspond to an engine coolant temperature, an engine oil temperature, or an exhaust gas temperature, to name just a few operating media temperatures. The term "operating media" are to be understood as such media, which are exposed as a result of internal combustion engine operation of the internal combustion engine temperature increase. It is particularly advantageous if the release is granted as a function of a plurality of mutually different operating medium temperatures. As a result, a reaching of component-specific limit temperatures can be detected particularly reliably, whereby a possible risk of incorrect injection can be at least largely prevented. Granting the release as a function of the at least one operating medium temperature has the advantage that it is possible to dispense with additional, so-called knock sensors, and instead to recourse to existing temperature sensors or calculation models stored in an engine control unit in order to detect whether the respective temperature limit value has been reached is.

In an advantageous embodiment of the invention, an engine coolant temperature is used as the at least one operating medium temperature. This is advantageous because the engine coolant temperature is a particularly meaningful quantity, by means of which it can be detected whether an internal combustion engine has warmed up and thus a release can be issued. The use of the engine coolant temperature can take place with particularly low expenditure, since the engine coolant temperature-which can also be referred to as the coolant water temperature-can be determined, for example, by means of temperature sensors already provided in the internal combustion engine. Thus, the effort to determine the engine coolant temperature can be kept very small.

In a further advantageous embodiment of the invention, an engine oil temperature is used as the at least one operating medium temperature. This is advantageous, since the engine oil temperature is also a particularly meaningful quantity, by means of which it can be recognized whether an internal combustion engine has warmed up and thus a release can be issued. The application of the engine oil temperature can take place with particularly little effort, since the engine oil temperature can be determined, for example, by means of temperature sensors already provided in the internal combustion engine. Thus, the effort to determine the engine oil temperature can be kept very small.

According to a further advantageous embodiment of the invention, an exhaust gas temperature is used as the at least one operating medium temperature. This is advantageous, since the exhaust gas temperature is a particularly meaningful size, in order to infer from this on reaching component-specific limit temperatures. When using the exhaust gas temperature can advantageously on existing exhaust gas temperature sensors or a Is exhaust gas temperature model of the internal combustion engine recourse.

According to a further advantageous embodiment of the invention, the release is granted only when a differential pressure value in a crankcase of the internal combustion engine is below a predetermined pressure limit. This is advantageous since a further increase in the differential pressure value in the crankcase can be effectively prevented as a result of any blowby of injected coolant at the respective piston rings of the internal combustion engine. This allows a particularly engine-friendly operation.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

Showing:

1 a flowchart showing exemplary method steps for the inventive method; and

2 a schematic representation of an internal combustion engine with a coolant injection device, which is designed for carrying out the method according to the invention.

1 shows an exemplary flowchart for the method according to the invention, which shows the operation of a in 2 schematically illustrated and presently designed as a water injection system coolant injection device 20 clarified.

The procedure is at a, in 2 schematically illustrated, in the present case designed as a gasoline engine internal combustion engine 1 carried out. The internal combustion engine 1 features with the coolant injector 20 a device, which is a coolant injection of a presently formed as water coolant 15 in a combustion air 4 the internal combustion engine 1 allows. The coolant 15 can also be referred to as a "cooling medium". The coolant injection device 20 has a plurality of coolant mixture formers 19 , wherein respective cylinders 2 the internal combustion engine 1 in each case a coolant mixture former formed as a water injection nozzle 19 assigned. The respective coolant mixture formers 19 can directly on the respective cylinders 2 be arranged and directly into a respective combustion chamber of the respective cylinder 2 inject what's in 2 but not shown. Alternatively - and as in this case 2 shown - can the coolant mixture former 19 also upstream of the cylinder 2 and downstream of a charge air cooler 9 be arranged.

The internal combustion engine 1 also has a gasoline direct injection, which by respective, on the cylinders 2 arranged and trained as injectors Gemischbildner 3 is clarified. Furthermore, an exhaust turbocharger in the form of an exhaust gas turbocharger 7 , which has a compressor 6 and a turbine 8th has provided. In addition, piston syringes not shown are provided here, which heat dissipation to each, in the cylinders 2 guided movable, but not shown piston of the internal combustion engine 1 allow by engine oil. In the 2 illustrated internal combustion engine 1 Thus, in summary and in the present case, has four cylinders arranged here in an exemplary manner in series 2 and the respective, into a combustion chamber of the cylinder 2 projecting injection nozzles (Gemischbildner 3 ) for the introduction of fuel.

The sucked combustion air 4 flows through an air filter 5 and then from the compressor 6 the exhaust gas turbocharger 7 which is the turbine 8th has compacted. The compressed combustion air 4 is by means of the intercooler 9 Heat extracted before the compressed combustion air 4 a throttle 10 flows through and the cylinders 2 the internal combustion engine 1 is supplied. After combustion becomes exhaust gas 11 of every cylinder 2 pushed out and the turbine 8th the exhaust gas turbocharger 7 fed. An exhaust gas mass flow 12 (the exhaust gas 11 ) is conducted to the environment after the exhaust gas mass flow 12 respective components of an exhaust aftertreatment 13 flowed through.

At the internal combustion engine 1 is the presently designed as a water injection system coolant injection device 20 arranged, wherein the coolant injection device 20 a reservoir formed as a water tank 14 for the coolant 15 (Coolant, here: water). The coolant 15 is through respective lines 16 from a feed unit designed as a water pump 17 promoted. The conveyor unit 17 may present upstream and downstream of the respective lines 16 promote and in particular the coolant 15 over a rail 18 to the coolant mixture formers 19 transport and the coolant 15 thus over the rail 18 on the mixture former 19 to distribute. Of the mixture formers 19 can out the coolant 15 by a coolant injection into the cylinders 2 supplied combustion air 4 be introduced.

In the following, the method according to the invention will be described with reference to FIG 1 described flowchart described. After starting in a step S1 starting a motor vehicle, which with the internal combustion engine 1 and the coolant injection device 20 is equipped, several substeps are performed in step S2. The sub-steps performed in step S2 include, for example, checking system readiness of the coolant injection device 20 wherein, for example, a venting of the lines 16 can be done or a defrosting of the coolant injection device 20 can be performed by means of a heating system not shown here at low ambient temperatures. In order to carry out the method, a control device (not further shown here) is provided, which has a release of a coolant injection of the coolant carried out in step S7 15 into the respective, through the cylinder 2 limited combustion chambers of the internal combustion engine 1 to start the coolant injection. The controller may also refuse the enable to inhibit the coolant injection. In order to grant the release in step S7, in the present embodiment, three mutually different temperature limit values of, accordingly, three, the internal combustion engine 1 relevant operating medium temperatures are cumulatively achieved, which is checked in steps S3, S4 and S5. Furthermore, the release is issued only when a differential pressure value in a crankcase of the internal combustion engine 1 is below a predetermined pressure limit, which is checked in step S6. The pressure limit is present at a maximum of 50 mbar overpressure compared to an ambient pressure. This pressure limit of 50 mbar represents a particularly suitable value to prevent excessive coolant entry into the engine oil of the internal combustion engine 1 to prevent.

In step S3, an engine coolant temperature is taken as a first operating medium temperature, and a first temperature limit of the engine _{coolant temperature is} T _coolant = 75 ° C. This first temperature limit of T _coolant = 75 ° C is particularly suitable for early coolant injection and thus excessive Motorölverdünnung by coolant entry into the engine oil, for example, by "blow-by" and additionally or alternatively by coolant attachment to the combustion chamber walls of the cylinder 2 , at least largely prevent.

In step S4, a motor oil temperature is used as a second operating medium temperature, with a second temperature limit of the engine oil temperature at T being _{engine oil} = 75 ° C. This second temperature limit of T _{engine oil} = 75 ° C is also particularly suitable for early coolant injection and thus excessive Motorölverdünnung by coolant entry into the engine oil, for example, by "blow-by" and additionally or alternatively by coolant attachment to combustion chamber walls of the cylinder 2 , at least largely prevent.

In step S5, an exhaust gas temperature is used as a third operating medium temperature, wherein a third temperature _{limit of} the exhaust gas temperature at ΔT _exhaust gas _limit = 50 K is below a predetermined exhaust gas _limit temperature. This third temperature _limit of ΔT _{exhaust limit} = 50 K below the predetermined exhaust temperature limit is also particularly suitable for early coolant injection and thus excessive Motorölverdünnung by coolant entry into the engine oil, for example, by "blow-by" and additionally or alternatively by coolant attachment to the combustion chamber walls of the cylinder 2 , at least largely prevent.

The steps S3 and S4 are therefore considered to be met if the respective engine coolant temperature or engine oil temperature is at least 75 ° C. On the other hand, step S5 is deemed to have been satisfied if the exhaust gas temperature is at most 50 K below the predetermined, third temperature limit value. If the steps S3 to S6 are satisfied, the release for the coolant injection is issued in step S7. In each of the steps S3 to S6, a loop is passed through in respective individual steps S11 and a renewed check of the individual steps S3 to S6 is carried out if the conditions there are not met. Even if the in 1 Of course, these steps S3 to S6 can also be checked simultaneously in order to achieve a particularly rapid granting or denying of the release.

If the criteria according to the steps S3 to S6 cumulatively fulfilled, as stated above, the release of the release in step S7 for coolant injection of the coolant takes place 15 , Whether and in what form the coolant 15 is injected, is determined in a subsequent step S8, wherein, for example, an injection quantity of the coolant 15 is determined. When step S8 is reached, as part of a permanent request for release in a loop designated by a step S9, steps S3 to S8 are run through in order to constantly check whether one of the steps S3 to S8 is not fulfilled and thus to refuse the release. By the permanent query of the release according to step S9, the coolant injection can be prevented immediately by not granting the release, if at least one of the steps S3 to S8 is not met or can not be fulfilled. In step S10, the internal combustion engine stops 1 or of the motor vehicle.

The inventive method allows the coolant injection into the internal combustion engine 1 by means of the coolant injection device 20 , where the coolant 15 from a primary fuel (here: petrol) of the internal combustion engine 1 is different. The method provides an effective measure for the protection of the internal combustion engine 1 before an engine damage due to excessive entry of the coolant 15 The main advantages associated with the method include avoiding engine damage by engine oil dilution, maximizing engine oil change intervals, and incorporating important criteria according to steps S3 through S8 for the operating strategy of the internal combustion engine 1 , which with the coolant injection device 20 for coolant injection of the coolant 15 Is provided. Other advantages that count by means of the method according to the invention include a CO ₂ reduction due to the possibility of further downsizing of the internal combustion engine 1 , the reduction of pollutant emissions as a result of omitted or lower mixture enrichment for component protection reasons, as well as the reduction of the thermal load of the internal combustion engine 1 just to name a few advantages.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

cylinder

3

Gemischbildner

4

combustion air

5

air filter

6

compressor

7

turbocharger

8th

turbine

9

Intercooler

10

throttle

11

exhaust

12

Exhaust gas mass flow

13

exhaust aftertreatment

14

reservoir

15

coolant

16

cables

17

delivery unit

18

Rail

19

Kühlmittelgemischbildner

20

Coolant injection device

S1

step

S2

step

S3

step

S4

step

S5

step

S6

step

S7

step

S8

step

S9

step

S10

step

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 102012207904 A1 [0006]
• DE 102014204509 A1 [0007]

Claims (5)

Method for operating a coolant injection device ( 20 ) for an internal combustion engine ( 1 ), in which by a control unit, a release of a coolant injection into a combustion chamber of the internal combustion engine ( 1 ) is issued (S7) to start the coolant injection and in which the release is denied to prevent the coolant injection, characterized in that the release is issued (S7) when a temperature limit of at least one of the internal combustion engine ( 1 ) operating medium temperature (S3, S4, S5) is reached. A method according to claim 1, characterized in that as the at least one operating medium temperature, an engine coolant temperature (S3) is used. A method according to claim 1 or 2, characterized in that as the at least one operating medium temperature, an engine oil temperature (S4) is used. Method according to one of the preceding claims, characterized in that as the at least one operating medium temperature, an exhaust gas temperature (S5) is used. Method according to one of the preceding claims, characterized in that the release is granted only (S7) when a differential pressure value in a crankcase of the internal combustion engine ( 1 ) is below a predetermined pressure limit (S6).

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