WO2012072346A1 - Fuel injection system for an internal combustion engine - Google Patents

Abstract

The invention relates to a fuel injection system (10) for an internal combustion engine, in particular a gasoline engine, comprising a high-pressure pump (30) for delivering fuel into a high pressure area (20) to upstream of at least one high-pressure injection valve (32) under high pressure, and a low-pressure area (18) for delivering fuel under low pressure to upstream of at least one low-pressure injection valve (26). According to the invention, the high-pressure pump (30) is designed or actuated such that it can only deliver, or that it only delivers, the fuel demand of the internal combustion engine when the internal combustion engine reaches idle running speed.

Description

 description

title

 Fuel injection system for an internal combustion engine prior art

The invention relates to a fuel injection system for an internal combustion engine, in particular a gasoline engine, with a high-pressure pump for conveying fuel in a high-pressure region before at least one high-pressure injection valve under high pressure and a low pressure region for supplying

Fuel at low pressure before at least one low pressure injector. Furthermore, the invention relates to an internal combustion engine, in particular a gasoline engine, with such a fuel injection system and a method for operating such a fuel injection system, in particular a dual fuel injection system.

A fuel injection system or "dual-injection system" is understood to mean a fuel injection system that is suitable for combustion

provided, usually liquid fuel, in particular gasoline, both in a suction pipe of an associated internal combustion engine (port fuel injection, PFI) and in the combustion chamber (direct injection, DI) can bring. In the PFI system is usually a low pressure and it is therefore referred to herein as the low pressure area. In the Dl system, however, the fuel is under high pressure, which is why this area of the fuel injection system is also referred to as a high pressure area. In such a fuel injection system, both low-pressure injection valves (PFI) injecting shortly before an inlet valve for fresh air and high-pressure injection valves (DI) injecting directly into the combustion chamber are installed. The amount of fuel supplied may be split or injected in full by one of the two types of injectors (DI or PFI). Such injection systems are already in gasoline or petrol engines in

Series production. They bring various advantages with it, in particular, the advantages of the above two injection modes can be combined depending on the operating condition of the internal combustion engine. The injection systems have to generate the low pressure on a low pressure pump, which also provides the fuel for a high pressure pump at the same time. The

High pressure pump then generates the high pressure for the high pressure area.

In fuel supply systems with two pumps in series and directly injecting into the combustion chamber fuel valves designed the

Starting process due to a low flow rate of the second fuel pump is relatively long. According to DE 19539885 A1 it is proposed to provide a valve device which ensures that during the starting process, the first

Fuel the fuel with increased feed pressure to the fuel

Fuel valves supplies. As a rule, this increased supply pressure is sufficient to start the internal combustion engine in the shortest possible time.

DE 10127516 A1 discloses a fuel system of an internal combustion engine comprising a fuel tank. Furthermore, at least one fuel pump is provided. With an outlet of the fuel pump is a fuel

Manifold connected, and in turn at least one fuel injection device is connected. To the starting behavior of the

To improve internal combustion engine, it is proposed that an additional, electrically driven fuel pump is provided, the outlet is connected directly to the fuel rail and which increased

 Supply pressure provides.

DE 10361579 A1 discloses a device for generating a

Injection pressure is injected with the fuel in at least one combustion chamber of an internal combustion engine. The device further comprises a

Low-pressure pump, which promotes fuel from a fuel supply with a pre-pressure, and a first high pressure pump, which promotes the pre-conveyed fuel with an increased pressure to an injection device. The device is characterized by a second high-pressure pump which, at a start of the internal combustion engine, also conveys the fuel, which is delivered with admission pressure, to the injection device at an increased pressure. In DE 19818421 A1 it is proposed that a first fuel pump works to eliminate problems during the starting process and at high fuel temperature with increased delivery capacity.

Finally, DE 10223077 A1 discloses a fuel injection system with a prefeed pump and a high-pressure pump, wherein between the

Pre-feed pump and the high-pressure pump, a low-pressure accumulator is provided. By means of the low-pressure accumulator, the running time of the prefeed pump can be reduced and thus the energy requirement of the fuel injection system can be reduced.

According to the invention, a fuel injection system for an internal combustion engine, in particular a gasoline engine, is provided with a high-pressure pump for delivering fuel to a high-pressure region upstream of at least one high-pressure injection valve under high pressure and a low-pressure region for supplying low-pressure fuel to at least one low-pressure injection valve. wherein the high-pressure pump is driven or designed so that they only from an idle speed of the internal combustion engine

required fuel promotes.

The fuel injection system includes a high pressure and a high pressure

Low pressure range, which fuel via fuel lines from a

Tank, preferably by means of a low-pressure pump, is supplied. The high pressure area is preceded by a high pressure pump, which increases the pressure of the fuel for the Dl range, namely for the high pressure injection. That is, the fuel passes through the low-pressure pump either to the low-pressure injectors and / or as pre-conveyed quantity

High pressure pump. Preferably, in the main conveying direction of the fuel, a line from the low-pressure pump initially leads to a branch, from which one branch in each case to the high-pressure pump, that is to the high-pressure region, and a line to the low-pressure injection valves. According to the invention, the high pressure pump is designed or controlled by means of a control unit such that the high pressure pump only from the

Idling speed of the internal combustion engine fuel consumption

Internal combustion engine can promote or promote. The high-pressure pump thus has a reduced delivery capacity at a lower speed.

An idling is understood to mean the operation of the internal combustion engine in which the engine does no work, that is, the engine is running without load. So that the engine keeps a certain engine-specific idling speed and does not come to a standstill, a small amount of a fuel-air mixture, the so-called idle gas is supplied during idling.

According to the invention, a fuel injection system is provided, which has a very simple structure and is inexpensive to manufacture.

It can also be used with a smaller size and simpler structure, a high-pressure pump than in conventional

Fuel injection systems. The high-pressure pump is equipped with a significantly reduced range of functions. In particular, the possibility of a high-pressure start is dispensed with. The high-pressure region, which is preferably designed as a so-called high-pressure rail, is preferably a

Fuel volume designed for normal operation without start.

By means of the fuel injection system according to the invention are in the

Direct injection various operating modes possible:

Among other things, a catalyst heating by means of a so-called

Homogeneous split operation done, whereby emissions are reduced after the start of the engine.

Furthermore, in particular in the upper load range of the engine, an increase of the charge can take place with predominant direct injection.

Furthermore, in the case of full-load operation of the engine, double injection is preferably carried out to improve the so-called knock properties. An uncontrolled combustion or auto-ignition of the fuel essentially becomes avoided. This leads to an under-consumption of fuel, so to a consumption advantage, as well as to a torque gain.

Finally, a so-called scavenging may preferably take place, with fresh and exhaust gases being mixed in a space between cylinder outlets and a turbocharger. This is preferably achieved by means of an overlap of discharge and inlet times of the gases. While an exhaust valve is still open, already opens a corresponding inlet valve, so that fresh gas flows into the combustion chamber of the cylinder. If the fresh gas mixes with the exhaust gases of the other cylinders, there is an increase in the oxygen content and thus a post-combustion of the gases. This effect is already at low engine speed, the exhaust gas volume and thus the speed of the

Turbocharger increased. On the one hand, the afterburning of the exhaust gases with fresh air leads to improved exhaust gas values. On the other hand, the charge pressure is increased as a result of the increase in the turbocharger speed at low engine speed and thus also the filling of the cylinder with fresh gas. This increases the efficiency of the combustion and thus the torque and the power of the engine.

The high-pressure pump is advantageously designed as a piston pump.

This piston pump is preferably compared to conventional ones

Piston pumps formed smaller, reducing costs in the production of

Be lowered fuel injection system. Furthermore, the space required for the high pressure area, in particular for the high pressure pump, can be made smaller. This leads to an overall smaller design of the fuel injection system.

According to an alternative advantageous development of the fuel injection system according to the invention, the high-pressure pump is designed as a rotor pump.

Since the high-pressure pump does not have to deliver fuel at a low starting rpm of the engine, but only at the higher engine idle speed, a rotor pump can also be used as an alternative to a piston pump. The rotor pump delivers the fuel substantially uniformly. The rotor pump, which is preferably two gears and a Enclosed with inlet and outlet, is robust and inexpensive due to the simple structure.

Furthermore, pressure pulsations in the low pressure range can be damped by using a rotor pump as a high pressure pump.

The rotor pump is preferably designed as a planetary rotor pump.

Such a development is advantageously very compact and leads to a reduction of the installation space and the manufacturing cost of the

 Fuel is not available.

In a further embodiment of the fuel injection system according to the invention, the high pressure pump is driven or designed such that the pumped amount of fuel from the idle speed, the maximum fuel demand of

Internal combustion engine, in particular the gasoline engine, nachfördern at full load operation can.

In such a development, the maximum flow rate of

High-pressure pump reduced from idle speed of the engine to about one-time the required amount of fuel at full load operation of the engine. By contrast, no high-pressure injection is necessary below the idling speed. In this development, the use of a rotor pump is particularly advantageous. There are advantageously reduced requirements for the

Components of high-pressure injection.

In a further embodiment of the fuel injection system according to the invention, the high-pressure pump is driven or designed such that in

High pressure range, a high pressure of less than 100 bar is set.

In the present case, it is sufficient if a constant pressure of preferably well below 100 bar is set.

In the high pressure fuel system, a mechanical pressure regulator is preferably present. For example, depending on the pressure level in the high pressure fuel system, the regulator affects the amount of fuel delivered to the high pressure pump, or the regulator relieves the excess flow delivered by the high pressure pump back into the low pressure circuit, or the pressure regulator combines these two principles.

The pressure regulator in the fuel injection system, in particular in

High-pressure region, in the present case can be designed mechanically, since a constant pressure in the high-pressure region is sufficient. Such a mechanical one

Pressure regulator is particularly cost effective in procurement. A so-called pressure holding or integrating a pressure accumulator is not necessary. Furthermore, in particular a high-pressure sensor can be dispensed with, which furthermore leads to a cost reduction.

The output stage of the at least one high-pressure injection valve may be formed with or without booster.

Furthermore, the high-pressure injectors are preferably the

Fuel quantity requirement of the internal combustion engine adjusted for Dl operation of the engine in full load. Preferably, the Dl injection amount may be increased by a e.g. 10% PFI content should be reduced to prevent coking. This results in lower demands on the Zumessbereich.

The object of the invention is also achieved by means of an internal combustion engine, in particular a gasoline engine, with such a fuel injection system according to the invention, with corresponding advantages, as mentioned above, can be achieved.

Finally, a method for operating the fuel injection system for an internal combustion engine is provided. The method comprises the following steps:

- Promote fuel in a high-pressure area before at least one

 High pressure injector under high pressure by means of a high pressure pump, and / or

- Supplying fuel in a low-pressure region under low pressure before at least one low-pressure injection valve, wherein the high pressure pump such is driven or designed so that it promotes fuel only at an idle speed of the engine.

By means of this design or control of the invention

Fuel injection system is provided a method that makes the operation of the fuel injection system very cost-effective.

An embodiment of the solution according to the invention is explained in more detail below with reference to the attached schematic drawing. It shows:

Fig. 1 is a diagram of an embodiment of a

 Fuel injection system according to the invention.

In Fig. 1 is a fuel injection system 10 according to the invention

illustrated in which from a tank 12 by means of an electric

Fuel pump (EKP) or low pressure pump 14 liquid fuel with about 5 bar pressure in a line 16 is promoted. The line 16 serves as a supply line to a low pressure region 18 and a high pressure region 20 of the

Fuel injection system 10. On the line 16, a pressure regulator 22 is provided, by means of which the pressure in the conduit 16 can be kept substantially constant. The pressure regulator 22 thus serves as an overpressure protection, that is, it is adapted to limit the present in the line 16 pressure to a predetermined maximum pressure.

A line 24 leads directly to the low-pressure region 18, so that there prevails the above-mentioned, provided by the low-pressure pump 14 pressure of about 5 bar. At the low-pressure region 18, which is designed tubular as a so-called low-pressure rail, four low-pressure injectors 26 are provided, of which the fuel, in this case gasoline, in a (not shown) intake manifold of an associated internal combustion engine can be injected (port fuel injection, PFI).

To the high-pressure region 20, a line 28, wherein in this line 28, a high pressure pump 30 incl. Pressure control is arranged by means of which the pressure of about 5 bar from the line 16 to preferably below 100 bar is raised and regulated. The associated fuel is then at the high pressure region 20, the is also designed as a tubular pressure chamber or as a so-called high-pressure rail, injected at four high-pressure injectors 32 directly in (not shown) cylinder of the internal combustion engine. This is also called

Direct injection (direct injection, DI).

The low-pressure pump 14 is preferably designed as an electrically driven pump and the high-pressure pump 30 in particular as a mechanically driven by a camshaft pump. The preferably integrated in the high-pressure pump 30 pressure control is usually carried out via a demand-based quantity control means of a quantity control valve (MSV).

The MSV shifts the unneeded high pressure fuel back into the low pressure system. The pressure control can also be purely mechanical and, for example, adjust the amount of fuel supplied to the high-pressure pump or let the amount pumped too much through the high-pressure pump flow back into the low-pressure circuit or combine both principles.

For example, with pure PFI operation, the high pressure pump 30 may not deliver fuel into the high pressure region 20. Accordingly, at each stroke of the high-pressure pump 30, the total quantity of fuel sucked back is preferably pushed back into the intake line 16 and thus to the so-called pressure side of the low-pressure pump 14.

According to the invention, the high-pressure pump 30 is designed or controlled by a control unit such that it can only promote or promote the engine fuel requirement from the idling speed. The possibility of a high-pressure start of the engine is dispensed with. So there is a reduced capacity, that is, a significantly reduced functionality of the

High-pressure pump 30 before: The pump 30 promotes at a cranking speed, which is lower than the idle speed, no or not enough fuel to cover the engine needs. In these cases, the engine fuel requirement is completely covered by PFI injections.

In particular, the amount of fuel that can be conveyed by the high-pressure pump 30 from the idling speed is the maximum engine requirement Quantity at full load operation of the internal combustion engine. The high-pressure rail is designed for a volume flow in normal operation without start.

The high-pressure pump 30 may therefore be formed as a piston pump 30 or as a rotor pump 30, such as a planetary rotor pump 30. When a

Piston pump 30 is used, it is designed smaller than in conventional fuel injection systems 10. These pump types have a simple construction in a small footprint and are also very cost-effective. During high-pressure injection, ie during Dl operation, the following operating modes are available, among others:

Catalyst heating may occur by means of a so-called homogeneous-split operation, thereby reducing emissions after engine start-up.

Furthermore, in particular in the upper load range of the engine, an increase of the charge can take place with predominant direct injection. Furthermore, a double injection occurs at full load operation of the engine

Improvement of the so-called knocking properties. Uncontrolled combustion or auto-ignition of the fuel is substantially avoided. Finally, a so-called scavenging done, with fresh and

Exhaust gases are mixed in a space between cylinder outlets and a turbocharger. On the one hand, an afterburning of the exhaust gases with fresh air leads to improved exhaust gas values. On the other hand, the charge pressure is increased as a result of an increase in the turbocharger speed at low engine speed and thus also the filling of the cylinder with fresh gas. This increases the

Effectiveness of combustion and thus the torque and power of the engine.

Furthermore, in the high-pressure region 20, a mechanical pressure regulator is interposed, which keeps the fuel pressure at a defined and constant level; on a high pressure sensor can be omitted. The high pressure injectors 32, that is, the high pressure injector output stages, are adapted for high pressure operation at full load of the engine, and high pressure operation may be reduced by a 10% PFI ratio to prevent coking.

Finally, it should be noted that all the features included in the

Application documents and in particular in the dependent claims, despite the formal reference made to one or more specific claims also individually or in any combination of independent

Protection should come.

Claims

A fuel injection system (10) for an internal combustion engine, in particular a gasoline engine, comprising a high pressure pump (30) for delivering fuel to a high pressure region (20) before at least one high pressure injector (32) at high pressure and a low pressure region (18) for supplying fuel below Low pressure before at least one low-pressure injection valve (26), characterized in that the high-pressure pump (30) is designed or driven so that they only from a motor-specific Idle speed can promote the required fuel demand of the engine. Fuel injection system (10) according to claim 1, characterized in that the high pressure pump (30) as a  Piston pump (30) is designed. Fuel injection system (10) according to claim 1, characterized in that the high pressure pump (30) as a  Rotor pump (30) is designed. Fuel injection system (10) according to claim 3, characterized in that the rotor pump (30) as a  Planetary rotor pump (30) is designed. Fuel injection system (10) according to any one of the preceding claims, characterized in that the high-pressure pump (30) is designed or driven such that the maximum fuel demand of Internal combustion engine can be promoted only from the idle speed of the engine by the high-pressure pump. 6. Fuel injection system (10) according to one of the preceding claims, characterized in that the high pressure pump (30) is driven such that in the high pressure region (20), a high pressure of less than 100 bar is set. 7. Fuel injection system (10) according to any one of the preceding claims, characterized in that the high pressure level in  Fuel injection system (10) is adjustable by a mechanical pressure regulator. 8. Internal combustion engine with a fuel injection system (10) according to one of claims 1 to 7. 9. A method for operating a fuel injection system (10) for a  Internal combustion engine according to one of claims 1 to 8, comprising the steps: - Promoting fuel in a high-pressure area (20) before at least one high-pressure injection valve (32) under high pressure by means of a  High pressure pump (30), and / or  Supplying fuel in a low-pressure region (18) under low pressure before at least one low-pressure injection valve (26),  characterized in that the high pressure pump (30) is controlled such that it promotes fuel only at an idling speed of the internal combustion engine.