DE10146051B4 - Fuel direct injection - Google Patents

Abstract

Direct fuel injection system for internal combustion engines for direct injection. from optionally at atmospheric pressure and room temperature liquid low pressure fuel or liquid gas in the liquid state in a combustion chamber of the internal combustion engine, with a high pressure part (B) and a fuel supply (A) with a medium pressure part (A1) for supplying liquid gas to the high pressure part (B), and with a low pressure part (A2) for supplying low pressure fuel and high pressure part (B), the medium pressure part (A1) having a fuel supply line for the liquid gas (12) with a solenoid valve (3) and a fuel pump for the liquid gas (4), and the low pressure part one Has fuel supply line for the low pressure fuel (1) with a check valve (2) and a first low pressure fuel pump and a second low pressure fuel pump (9), and wherein the first and the second low pressure fuel pump are arranged so that their pressures add up.

Description

The invention relates to a direct fuel injection system for internal combustion engines for direct injection. optionally at atmospheric pressure and Room temperature liquid Low pressure fuel or liquefied petroleum gas in liquid Physical state in a combustion chamber of the internal combustion engine and a Method for controlling such a direct fuel injection system.

Liquefied petroleum gas, also LPG (L quified petroleum gas) or also called LPG, is a propane-butane mixture with von Region to region different mixture proportions due to storage under relatively low overpressure (approx. 7-8 bar at room temperature) in liquid Form in the fuel tank (for this reason further here referred to as "medium pressure fuel", in demarcation to the fuels that are liquid at room temperature and atmospheric pressure, “low-pressure fuels” such as gasoline, diesel or similar.), at atmospheric pressure but gaseous is.

In the previously known i and on available on the market Feeding systems of LPG in the LPG squeezed into the combustion chamber of an internal combustion engine from the special, pressure-resistant liquid gas tank (blow-off pressure of the pressure safety valve: 30 bar) due to its own excess pressure an evaporator pressure regulator, where it, by reducing the overpressure and fed by Thermal energy to compensate for the evaporative cold, from the liquid in the gaseous Condition transferred and in this gaseous gene Physical state was supplied to the intake manifold of the engine. Either sucked in by the negative pressure of the combustion air flowing in the intake tract or by, via a Regulation regulated, active blowing in front of the intake valves the internal combustion engine.

The current state of the art in the supply of liquid gas represents the supply of the liquid gas into the intake tract in the liquid state, a pump in conjunction with a pressure regulator ensuring the constant pressure of the liquid phase in front of the injection valves, see the EP 0 725 208 B1 ,

State of the art in the supply of gasoline or diesel or something similar, at atmospheric pressure and room temperature liquid, Fuels (here further delimited from liquid gas referred to as "low pressure fuel") direct injection, in which the fuel is injected at high pressure the combustion chamber of the internal combustion engine is injected directly with stratified cargo at partial load. Their technology is known and is therefore not explained further here.

However, direct injection engines can be used with the previously used fuel supply configurations be operated as a direct injection system with liquefied petroleum gas because she the for it necessary operating pressures and did not reach fuel temperatures at the high pressure pump inlet.

For the bivalent operation of internal combustion engines with petrol or diesel or similar, in combination with liquid gas have been for each fuel uses its own fuel delivery system. This has a relatively high construction cost. The continues Injection of liquid gas before the intake valves still to oust air sucked in by the evaporating fuel gas and thus for reduction available for combustion standing mixture mass.

Also with the injection of fuel upstream of the intake valves no operation with stratified charge possible.

From the JP 59162337 AA , Patent Abstracts of Japan, a direct fuel injection system is known in which liquefied petroleum gas and diesel fuel are supplied to a direct fuel injection system. However, this is mixed, without switching from one type of fuel to the other.

Advantages of invention

These problems are solved by the features of claim 1, which is a direct fuel injection system concerns, and by the features of the independent claim 16, which is a method for controlling such a direct fuel injection system concerns, and by the features of the respective subclaims.

• a) auch Flüssiggas direkt und flüssig in den Brennraum einer Brennkraftmaschine eingespritzt werden kann, und daß
• b) durch das Zusammenführen der Benzin- und Flüssiggaskraftstoffleitungen vor der Hochdruckpumpe des Einspritzsystems, mit einem einzigen Einspritzsystem wahlweise sowohl Niederdruckkraftstoffe (Benzin oder Diesel oder ähnliches), als auch Mitteldruckkraftstoff (Flüssiggas = Autogas = LPG = Liquified-Petroleum-Gas) oder ein Gemisch aus beidem direkt in den Brennraum einer Brennkraftmaschine eingespritzt werden kann.

The present invention causes

• a) also liquid gas can be injected directly and liquid into the combustion chamber of an internal combustion engine, and that
• b) by merging the gasoline and liquid gas fuel lines in front of the high-pressure pump of the injection system, with a single injection system either low-pressure fuels (gasoline or diesel or similar), as well as medium-pressure fuel (liquefied petroleum gas = LPG = liquified petroleum gas) or a mixture both can be injected directly into the combustion chamber of an internal combustion engine.

• a) Flüssiggas ist ein Produkt, welches bei der Herstellung von Benzin oder Diesel automatisch anfällt. Seine Nutzung erhöht somit die Ausnutzung des Rohöls.
• b) Gegenüber Systemen mit Benzindirekteinspritzung: 1. die höhere Energiedichte (ca.2%) des LPG-Luft-Gemisches steigert die Leistung 2. die höhere Oktanzahl von LPG und die bessere innere Gemischkühlung erlauben eine höhere Verdichtung, die wiederum auch bei Volllast den Wirkungsgrad, das Drehmoment und die Leistung steigert. 3. die Rohemissionen von umweltbelastenden Schadstoffen verringert sich, insbesondere beim Kaltstart, weil eine Anfettung des Kraftstoff-Luftgemisches nicht nötig ist. 4. die CO2-Emission verringert sich um bis zu 20 % 5. da Flüssiggas so gut wie kein Schwefel enthält wird die Abgasreinigung vereinfacht 6. gesundheitsschädiche toxische Emissionen von PAK, Aldehyden, Benzol, Toluol vermindern sich 7. keine Grundwassergefährdung durch LPG, da es nicht wasserlöslich ist 8. die Lebensdauer von Motor und Zündkerzen verlängert sich durch die Verminderung aggressiver Säuren und Kohlenstoffablagerungen und geringere Verwässerung des Schmieröls.
• c) Gegenüber Flüssiggassystemen mit Saugrohreinspritzung: 1. Reduzierter Kraftstoffverbrauch durch die Direkteinspritzung. Im europäischen Fahrzyklus (NEFZ) beträgt die Einsparung gegenüber Motoren mit herkömmlichen Einspritzverfahren 15 – 20 % Kraftstoff. Hinzu kommt noch die Kraftstoffeinsparung durch die vollstandige Füllung der Zylinder mit Verbrennungsluft, so daß Kraftstoffeinspurungen bis zu 30 % möglich sind, 2. es wird kein zweites Einspritzsystem benötigt und auch keine zusätzliche Regelfunktion für ien Mitteldruckkraftstoff, wie in EP 0 725 208 B1 beschrieben.

Further advantages of the invention:

• a) Liquefied petroleum gas is a product that is automatically generated in the production of petrol or diesel. Its use thus increases the utilization of the crude oil.
• b) Compared to systems with direct petrol injection: 1. the higher energy density (approx. 2%) of the LPG-air mixture increases the performance 2. The higher octane number of LPG and the better internal mixture cooling allow a higher compression, which in turn increases efficiency, torque and performance even at full load. 3. The raw emissions of polluting pollutants are reduced, especially during a cold start, because the fuel-air mixture does not need to be enriched. 4. CO2 emissions are reduced by up to 20%. 5. Since liquid gas contains practically no sulfur, exhaust gas cleaning is simplified. 6. Harmful toxic emissions of PAHs, aldehydes, benzene and toluene are reduced. 7. No groundwater hazard due to LPG, because it is not water-soluble 8. The life of the engine and spark plugs is extended by the reduction of aggressive acids and carbon deposits and less dilution of the lubricating oil.
• c) Compared to liquid gas systems with intake manifold injection: 1. Reduced fuel consumption through direct injection. In the European driving cycle (NEDC), the saving compared to engines with conventional injection methods is 15 - 20% fuel. In addition, there is the fuel saving through the complete filling of the cylinders with combustion air, so that fuel savings of up to 30% are possible. 2. There is no need for a second injection system and also no additional control function for a medium-pressure fuel, as in EP 0 725 208 B1 described.

drawings

Embodiments of the invention are shown in simplified form in the drawings and in the following Description explained.

Show it:

1 the system areas of direct fuel injection,

2 a monovalent version of the direct fuel injection system for the medium pressure fuel liquefied petroleum gas in the variant with two fuel return lines from the high pressure area, which return the unused fuel to the tank;

3 a monovalent version of the direct fuel injection system for the medium pressure fuel liquid gas in the variant with the fuel return to the fuel supply line in front of the high pressure pump,

4 a bivalent variant according to the invention for medium-pressure and low-pressure fuels. This variant is characterized by two fuel return lines in the low-pressure system, which end in the low-pressure fuel tank.

5 also shows a bivalent version. It differs from that in the arrangement of high pressure pump and high pressure regulator in the high pressure section 4 shown variant. In addition, it has only one fuel return line, which also does not end in the tank, but opens into the fuel supply line in front of the high-pressure pump.

Description of the embodiments

The invention is based on the market commercial Internal combustion engines with a direct injection system for low pressure fuels.

For this reason, in 1 only the common interaction of the system areas fuel supply A (consisting of a medium-pressure fuel supply A1 or a medium-pressure fuel supply A1 and a low-pressure fuel supply A2), high-pressure part B, the electronic control C and the periphery D and the further explanation of the areas B , C and D are dispensed with, since one of the advantages of the invention described here is that there is no need to intervene in these areas for direct injection in order to inject liquid gas directly.

In 2 A monovalent version of the direct fuel injection system is shown, in which the low-pressure fuel system A2 is replaced by a medium-pressure fuel system A1. From a medium pressure resistant fuel tank 10 (Blow-off pressure 30 bar) via a filling line 11 is filled, presses after opening the solenoid valve 3 LPG 18 into the supply line 12 flows through the fuel cooler 14 and then arrives at the inlet of the medium pressure fuel pump 4 , The fuel pump 4 increases the pressure of the liquid gas 18 and thus ensures together with the low pressure pressure regulator 6 making sure that the LPG 18 in the liquid state at the inlet of the high pressure pump 5 arrives. In order for this to be guaranteed even during temperature peaks caused by heat conduction and heat radiation from the internal combustion engine to the high-pressure fuel pump close to the engine, the vapor pressure of the LPG at the high-pressure pump inlet must always be lower than the total pressure of the fuel in the fuel circuit A. This is caused by heating the LPG in the fuel tank 10 reached. Is shown in 2 the variant with an electric heating element placed in the fuel tank 23 as a heat source. The fuel heating is switched on when the difference in temperature measurements between the two temperature sensors 17 exceeds a predetermined setpoint, it is switched off when the temperature difference falls below another predetermined setpoint. In addition, the heating has 23 a temperature limit for safety reasons.

The high pressure pump 5 compresses the liquefied gas with a low-pressure fuel the fuel density factor (density of low-pressure fuel to density of liquefied petroleum gas) and the air requirement factor changed pressure in the combustion chamber of the internal combustion engine, regulated by the electronic control C. Unused, excess fuel is fed via the return lines 16 and 19 in the liquid gas tank 10 recycled.

3 also shows a monovalent version of the liquid gas direct injection but with a different configuration of the high pressure part B. Here are rails 7 and high pressure regulator 8th connected and the excess fuel is not in the fuel tank but in front of the high pressure pump 5 fed back into the feed line.

The 4 explains the hydraulic circuit diagram of a direct fuel injection system according to the invention with a branch line in the fuel supply line for supplying gasoline or diesel to the liquid gas tank and two separate fuel return lines to the fuel tank. A medium-pressure fuel system A1 with a supply line is shown 1 from the low pressure fuel tank (not shown) leading to a high pressure fuel pump 5 leads. Via the fuel rail (common rail) 7 leads the high-pressure fuel line to the high-pressure fuel regulator 8th , Both from the high pressure regulator 8th as well as from the high pressure fuel pump 5 runs a fuel return line 16 back into the fuel tank.

To the low pressure fuel line 1 the supply line for the liquid gas is connected with a T-piece, which comes from the pressure tank 10 for the liquefied gas comes. Through solenoid valves ( 3 ) in combination with check valves 2 it is ensured that fuel from only one of the two fuel tanks to the high pressure pump 5 flows and the liquid gas with its higher pressure level does not press into the low-pressure fuel tank.

The second fuel pump 9 in this line is used for a brief pressure increase in the low-pressure fuel system in the phase of switching from the liquid gas mode to the low-pressure fuel mode. Without this second fuel pump 9 would turn off after the medium pressure fuel pump 4 the pressure level in the fuel supply lines 1 and 20 decrease to the pressure level of the low pressure circuit, i.e. below the pressure that prevents the liquefied gas from evaporating. However, there are liquid gas residues in the injection system at the time of switching and also for a while afterwards, which are prevented from evaporating by the increased pressure. The increased pressure is in the low pressure mode of operation by the second low pressure fuel pump 9 Maintained until all liquid gas in the entire pipeline system has been replaced by low-pressure fuel.

The fuel pump 4 increases the pressure of the liquefied gas and thereby ensures that the liquefied petroleum gas, even when heated, the HP pump 5 reached in the liquid state. A fuel cooler serves the same purpose 14 that in front of the fuel pump 4 is appropriate. Exceeds the fuel temperature difference between the fuel tank 10 and high pressure pump inlet 5 a critical value (approx. 30 ° C), then the temperature sensor 17 the cooling process starts, in which cooling by an evaporating medium, either by the refrigerant of the cooling circuit of the air conditioning system or a branched-off part of the liquid gas 18 is effected. The version with branched liquid gas is shown 18 , Through the temperature sensor 17 becomes the solenoid valve 21 switched that the LPG the way to the throttle 24 of the fuel cooler 14 releases where it evaporates and cools the fuel through its evaporative cooling. The gaseous fuel is then fed to the intake manifold of the engine via the vaporized fuel circuit.

The additional fuel pump 9 also opens up the possibility of a further branch line 13 that in the return line for the LPG 16 opens and together with this into the filling line 11 for the liquefied petroleum gas, pumping low-pressure fuel into the liquefied petroleum gas tank, whereby a low-pressure fuel-liquefied gas mixture with freely selectable mixture proportions can be generated. This process is controlled by a separately switchable solenoid valve 15 , By adding low pressure fuel to the LPG, lubrication problems in the system are avoided.

The low pressure control valve 6 ensures constant pressure at the inlet of the high pressure fuel pump 5 ,

From the fuel supply line 20 branches in front of the high pressure pump 5 a control line 22 from the control piston of the high pressure regulator 8th during operation with liquefied petroleum gas, a pressure is added which is added to a spring tension and thereby generates the necessary higher injection pressure in liquefied gas mode.

In liquefied petroleum gas operating mode, the excess liquefied gas that is conveyed beyond the engine's requirements is fed via the return line for the medium-pressure fuel 19 into the LPG fill line 11 from there and returns to the LPG tank 10 , check valves 2 prevent the liquid gas from escaping 18 ,

The invention has advantages on several levels. Because the liquid gas is now injected directly and liquid into the combustion chamber, it no longer displaces intake air. This increases the degree of filling of the cylinders compared to injection into the intake tract and thus also the performance of the engine. At the same time, all advantages of the direct injection process are retained. The second level of advantage is the structural simplification of the liquid gas system. The gas-air mixer, the evaporator pressure regulator, the fuel pump and injectors for the liquid gas fall away. A separate measurement and control system for the liquefied petroleum gas is also unnecessary, since the liquid state of the two fuels means that the existing system for low-pressure fuel can be used for both types of fuel.

5 also shows a bivalent version of the direct fuel injection but with a different configuration of the high pressure part B. Here are rails 7 and high pressure regulator 8th connected to each other and the excess fuel is not here via the fuel return line 16 in the fuel tank, but in front of the high pressure pump 5 back into the feed line 20 recycled.

A fuel tank for LPG is shown 10 from which a fuel line 12 leads away and a direct injection system B, consisting of a high pressure pump 5 , a manifold 7 with high pressure lines leading to high pressure injectors 21 and a pressure control valve 8th , from which a fuel return line 16 before the high pressure pump 5 in d: e common fuel supply line 20 empties. The functionality of the modules otherwise corresponds to 4 ,

1

Low-pressure fuel line

2

check valve

3

magnetic valve

4

Fuel pump the medium pressure fuel supply (LPG system)

5

high pressure pump

6

Low-pressure regulator

7

Fuel rail (Common rail)

8th

High pressure regulator

9

Second Low pressure fuel supply fuel pump

10

flameproof Tank for medium pressure fuel (LPG)

11

filling line the medium pressure fuel supply

12

supply for the Medium-pressure fuel

13

Short line

14

Fuel cooler

15

magnetic valve in the short-circuit line

16

return for the Low pressure fuel 1

17

Temperature sensor for the medium pressure fuel temperature

18

LPG (LPG)

19

return for the Medium-pressure fuel

20

common Fuel line

21

magnetic valve for the Coolant supply

22

control line

23

Heating fuel

24

throttle

Claims (24)

Direct fuel injection system for internal combustion engines for direct injection. from optionally at atmospheric pressure and room temperature liquid low pressure fuel or liquid gas in the liquid state in a combustion chamber of the internal combustion engine, with a high pressure part (B) and a fuel supply (A) with a medium pressure part (A1) for supplying liquid gas to the high pressure part (B), and with a low pressure part (A2) for supplying low pressure fuel and high pressure part (B), the medium pressure part (A1) having a fuel supply line for the liquid gas ( 12 ) with a solenoid valve ( 3 ) and a fuel pump for the LPG ( 4 ), and the low-pressure part has a fuel supply line for the low-pressure fuel ( 1 ) with a check valve ( 2 ) and a first low pressure fuel pump and a second low pressure fuel pump ( 9 ), and wherein the first and second low pressure fuel pumps are arranged so that their pressures add up. Direct fuel injection system according to claim 1, characterized in that the added pressures of the first low-pressure fuel pump and the second low-pressure fuel pump ( 9 ) are above the vaporization pressure of propane. Direct fuel injection system according to claim 1, characterized in that the fuel supply line for the liquid gas ( 12 ) and the fuel supply line for the low pressure fuel ( 1 ) are brought together upstream of the high pressure part (B). Direct fuel injection system according to claim 1, characterized in that an adjustable cooling device ( 14 ) in the fuel supply line for the LPG ( 12 ) is provided. Direct fuel injection system according to claim 4, characterized in that the controllable cooling device ( 14 ) is cooled by evaporating refrigerant in an air conditioning system. Direct fuel injection system according to claim 4, characterized in that the controllable cooling device ( 14 ) is cooled by evaporating liquid gas. A direct fuel injection system according to claim 6, characterized in that the vaporized liquefied gas is an intake system fed to the internal combustion engine becomes. Direct fuel injection system according to one of Claims 1 to 7, characterized in that the high-pressure part (B) is a high-pressure pump ( 5 ), a manifold ( 7 ) and a high pressure control valve (8). Fuel direct injection system according to claim 8, characterized in that starting from the High pressure pump ( 5 ) and the high pressure control valve ( 8th ) Return lines ( 16 ) are provided for a container for the low-pressure fuel, each of which has a solenoid valve ( 3 ) and upstream of the solenoid valves ( 3 ) Branches to a container for the liquid gas ( 10 ) exhibit.. Fuel direct injection system according to one of claims 8 or 9, characterized in that the high pressure control valve ( 8th ) can be controlled hydraulically by diverting fuel from the fuel supply (A). Direct fuel injection system according to one of the claims 1 to 10 , characterized in that downstream of the junction of the fuel supply line for the liquid gas ( 12 ) and the fuel supply line for the low pressure fuel ( 1 ) and upstream of the high pressure part (B) a fuel line ( 13 ) branches off. Direct fuel injection system according to claim 11, characterized in that the fuel line ( 13 ) to a liquid gas filling line ( 11 ) for the container for the liquid gas ( 10 ) is performed. Direct fuel injection system according to claim 11, characterized in that the fuel line ( 13 ) to one of the return lines ( 16 ), upstream of the solenoid valves ( 3 ), is led. Direct fuel injection system according to one of claims 11 to 13, characterized in that the fuel line ( 13 ) by a solenoid valve ( 15 ) can be opened or closed. Direct fuel injection system according to one of claims 1 to 14, characterized in that a fuel volume flow measuring device is provided is. Method for controlling a direct fuel injection system according to one of Claims 1 to 15, characterized in that the magnetic valve ( 3 ) in the medium pressure section (A1) is opened, the fuel pump for the liquid gas ( 4 ) is switched on and the first low-pressure fuel pump is switched off. Method for controlling a direct fuel injection system according to one of claims 1 to 15, characterized in that for switching from operation with liquid gas to operation with low pressure fuel, the solenoid valve ( 3 ) in the medium pressure section (A1) is closed, the fuel pump for the liquid gas ( 4 ) is switched off and the first low-pressure fuel pump is switched on. Method for controlling a direct fuel injection system according to claim 17, characterized in that when switching from operation with liquefied petroleum gas to operation with low pressure fuel, the second low pressure fuel pump ( 9 ) is switched on for a short time. Method for controlling a direct fuel injection system according to claim 18, characterized in that during the connection of the second low-pressure fuel pump ( 9 ) the solenoid valves ( 3 ) in the return lines ( 16 ) are kept closed. Method for controlling a direct fuel injection system according to claim 19, characterized in that the solenoid valve (for admixing low pressure fuel to the liquid gas ( 15 ) is opened. Method for controlling a direct fuel injection system according to claim 19, characterized in that the connection of the second low-pressure fuel pump ( 9 ) and keeping the solenoid valves closed ( 3 ) in the return lines ( 16 ) is maintained until the liquid gas is replaced by low-pressure fuel in all lines of the direct fuel injection system. Method for controlling a direct fuel injection system according to claim 21, characterized in that the shutdown of the second low-pressure fuel pump ( 9 ) and opening the solenoid valves ( 3 ) in the return lines ( 16 ) are controlled at the same time on the basis of the discontinuous signal of the fuel volume flow measuring device which results when switching from operation with liquid gas to operation with low pressure fuel. Method for controlling a direct fuel injection system according to one of claims 16 to 22, characterized in that the by the high pressure pump ( 5 ) generated injection pressures by the high pressure control valve ( 8th ) be changed reciprocally to the fuel densities and reciprocally to the air consumption figures of the liquid gas or the low-pressure fuel. Method for controlling a direct fuel injection system according to one of claims 16 to 23, characterized in that the control of the cooling device ( 14 ) by switching on or off depending on the temperature of the liquid gas.