DE102005000612A1 - Starting process for internal combustion engine involves setting starting requirements before starting, and operating ignition and direct injection at setting - Google Patents

Abstract

The starting process is for an internal combustion engine with direct fuel injection. When the engine is started, the ignition and the direct fuel injection are operated at starting parameters. Before the start, the starting requirement can be set. The ignition and the direct fuel injection will then be operated at these pre-start parameters.

Description

The The invention is based on a method for operating an internal combustion engine with a direct fuel injection according to the preamble of the independent claim.

object The present invention also provides an apparatus for direct fuel injection and a controller for the application of the method according to the invention.

It is known when starting an internal combustion engine while the Crankshaft starts up to startup speed, inject fuel, around the surfaces to wet the combustion chamber and at the same time an ignitable mixture for the to provide the first combustion. Especially with a cold start at low temperatures can very big Condensate fuel quantities on the relevant surfaces and stand a subsequent combustion is not available. The injection quantity must in the direction of lower temperatures continue to be increased to a safe Start the engine to ensure.

Farther it is common in systems with high pressure direct injection, high pressure pumps and also injectors for the To design fuel consumption of the internal combustion engine in the full load. With this interpretation can for very low temperatures, the necessary fuel in the disposal no longer be injected. This leads, for example to a pressure drop in the fuel system, in particular in the pressure accumulator and makes starting the engine difficult or makes it impossible.

Especially injectors for high pressure injections have a small cross-section, whereby the amount of fuel, the maximum can be injected, compared to low pressure system strong limited becomes.

From the DE 100 56 863 is a method for port injection of fuel during the starting phase of an internal combustion engine is known in which to build a wall film in the cylinders and simultaneously providing an ignitable mixture for the first combustion so-called pre-injectors are sold according to a certain strategies in a suction pipe. In order to avoid that the pre-fillings are too rich or too lean during the start-up phase, in the method the fuel quantities of the pre-injection are chosen differently depending on the expected fillings of the respective cylinders.

The inventive method with the characteristics of the independent Claim has in contrast the advantage that before a start in the presence of a start request, the ignition and fuel direct injection operated with pre-start parameters become.

This Approach is especially in injection systems with high system pressures and small cross sections of the high-pressure injection valves advantageous, especially at low temperatures, start-up measures are initiated, the subsequent start of the internal combustion engine facilitate.

Farther this approach has the advantage that the injection with each present and possible Fuel pressure can be done without, for example, to a higher fuel pressure, which would possibly be generated by a second fuel pump, maintained must become.

By in the subclaims listed activities are advantageous developments and improvements of the independent claim specified method possible.

Especially It is advantageous if the pre-start parameters for the ignition are selected such that no or essentially no combustion of one in the combustion chamber located fuel. This has the advantage that during a Pre-injection in a starting internal combustion engine, i. when the starter moves the crankshaft, by a typically already in operation ignition of the injected fuel can not ignite in an uncontrolled manner.

Especially It is advantageous if the start of the internal combustion engine is only initiated when a fuel pressure exceeds a pressure threshold Has. So the start is not in a low pressure area, but as a high pressure start.

According to one Further advantageous development, it is provided that the Pre-start parameters for the direct fuel injection are chosen such that fuel is independent of Recognition of working cycles of cylinders an injection in at least one of the combustion chambers the internal combustion engine takes place. This has the advantage of being at a standstill or at the first start of the crankshaft, at a time when typically a synchronization is not given already Fuel in the combustion chambers can be introduced.

According to another embodiment of the invention, it is provided, working cycles of Determine internal combustion engine, and to inject fuel into the combustion chambers prior to a start in sequence of the determined work cycles, either no ignition takes place or the ignition is performed in such a way that substantially no combustion takes place. This has the particular advantage that when the power strokes are already known in the presence of a start request or can be determined in a suitable manner, the fuel according to the running with the rotation of the crankshaft power strokes of the individual cylinders can be selectively injected at an advantageous time / crankshaft angle.

Farther it is provided that the second fuel pressure, in particular a high pressure is built up by a second fuel pump. So can the pressure generation for the different pressure ranges in an advantageous manner with different for each Pressure range optimized fuel pumps done.

According to one Further advantageous development, it is provided, regardless of the presence of a synchronization of the power strokes with the crankshaft inject.

Further It is advantageous, the first fuel pump already when you press a vehicle door put into operation, so that at a subsequent start request, eg by pressing the ignition key already a sufficient first fuel pressure is available.

According to one Another advantageous embodiment is a device for direct fuel injection provided with a first and second fuel pump, wherein the Fuel pumps each have a first and second fuel pressure generate, and with at least one injection valve per cylinder, being a control device in the presence of a start request, the injection valves actuated such that fuel at the same time in all combustion chambers the internal combustion engine passes.

drawings

Further Features, applications and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention shown in the drawings. Make up all features described or illustrated alone or in any combination the subject of the invention, regardless of its summary in the claims or their relationship as well as independent of their formulation or presentation in the description or in the drawings.

It shows:

1 schematically a device for direct fuel injection.

description the embodiments

The inventive method is both for Low-pressure fuel supply systems as well as for high pressure fuel delivery systems applicable, wherein the fuel supply systems at least one fuel pump include, independent can be operated by the operating condition of the internal combustion engine.

It is known that at low ambient temperatures and a corresponding cooled Internal combustion engine of injected at startup fuel to one huge Part on the surfaces condensed in the combustion chamber. For example, for a start at - 30 ° C up to 16 times more fuel needed as for an operation in full load.

The Invention goes from consideration out during the needed a start additional Fuel quantity - eg. due to low temperatures - before to inject the start of the internal combustion engine.

In 1 is an example of a device 1 shown for direct fuel injection of a four-cylinder internal combustion engine. The device 1 has a first fuel pump 10 on, with the fuel from a fuel tank 50 towards a second fuel pump 20 is pumped. The first fuel pump 10 is suitable for generating a low pressure. The second fuel pump 20 Promotes the fuel in a pressure accumulator 30 and increases from the first fuel pump 10 provided low pressure on a high pressure. The accumulator 30 , often referred to as Rail or Common Rail, is in turn with four injectors 40 connected. In the 1 illustrated device for fuel supply is used in the present example, the injectors 40 a four-cylinder internal combustion engine with sufficient fuel and necessary fuel pressure to supply, so that a reliable injection and safe operation of the internal combustion engine is ensured.

To promote fuel during standstill of the internal combustion engine is the first fuel pump 10 preferably designed as an electric fuel pump. Although the second fuel pump can also be made electrically operable, but is predominantly coupled directly to the crankshaft or other shaft of the internal combustion engine, so at standstill of the Brenn engine no additional pressure through the second fuel pump 20 is built.

It is according to the invention intended to distinguish between a pre-start and a start phase. At a start of the internal combustion engine, at least the ignition and also the direct fuel injection with typical starting parameters operated. The star parameters are usually chosen so that the internal combustion engine reaches an idling speed in a short time. While a pre-launch phase is planned, ignition and Injection device with for to operate the respective start condition adapted pre-start parameters.

The Pre-start phase preferably starts when there is a start request for example, by pressing of the ignition key and Choice of ignition position. Of course Other conditions are conceivable, by which a start request and thus a start of the pre-start phase can be triggered.

Lies now a start request, it is first checked, which starting conditions available. Depending on the starting conditions, eg warm start, cold start, etc. are different fuel amounts for the start provided. For example It can be provided, in a warm start only small amounts in advance inject or completely to an advance injection without. When a cold start is detected, for example, based on the Motor temperature, ambient temperature, etc. an injection quantity or injection strategy for the Pre-start phase and possibly also for the start of the internal combustion engine can be determined. The dependent the starting conditions selected Parameters form the pre-start parameters. These parameters can, for example. be stored in a map and / or based on detected state or Operating variables determined become.

It is according to the invention also provided the ignition the internal combustion engine with suitable Vorstartparametern to operate. In particular, it is intended to ignite the ignition in the pre-starter phase to operate so that the introduced fuel does not ignite. This On the one hand can be done by the ignition in the pre-start phase is not operated or, secondly, that the ignition operated in such a way becomes that a generated spark the fuel is typically not inflamed and thus no combustion is initiated. This can be achieved, for example, by the ignition angle clearly after late is shifted, possibly even up to the exhaust stroke of the cylinder.

By Such a procedure avoids that the injected fuel already burned completely or partially before the start and then for the start of the internal combustion engine is no longer available.

With the start request or possibly even earlier, the first fuel pump 10 operated to a pressure in the fuel system and in particular in the pressure accumulator 30 and at the injectors 40 build. With the existing pressure is then least one cylinder - but preferably each cylinder - filled with a certain amount of fuel and then started the engine. Alternatively, this injection can be carried out before the start request. To trigger this process, for example, a door contact switch can be used.

If a second fuel pump 20 may be present, which impedes the passage of fuel at low start-up speeds, it may be provided to bridge the second fuel pump with a detour line during the construction of the first fuel pressure.

According to the invention, it is provided, first with a first fuel pump, a fuel pressure in the pressure accumulator 30 build. This can be done, for example, in the presence of a start request with the start of the start phase, ie with switching on the ignition or even before the start of the starting phase, for example, already when opening the vehicle door by a contact switch. However, other times and / or triggering mechanisms for starting up the first fuel pump are also conceivable.

In the pre-start so preferably at a first start the Crankshaft is at least in one possibly in each cylinder of the Internal combustion engine a defined injection quantity with the available Fuel pressure injected without an ignition is initiated or an ignition the fuel is ignited. Then the start of the internal combustion engine takes place with typical start parameters, for example with start parameters for one High-pressure start.

Of Furthermore, it may be provided that the ignition in the pre-start phase is adjusted so that at least part of the injected fuel burns. Preferably, such combustion takes place in such a way that substantially no torque is generated and the heat of combustion the Internal combustion engine heated. In particular, it can be provided with the help of multiple injections be a part of the injected fuel for a first combustion and another part for the Wetting of the combustion chamber surfaces use.

Before a high-pressure start is initiated, It may further be provided that initially waited whether the fuel pressure has exceeded a pressure threshold necessary for a high-pressure start.

By this pre-injection will be the amount of fuel needed during take-off significantly reduced. So it can be provided that with the pre-injection the amount of fuel injected for a given operating condition typically condensed on the combustion chamber walls, so that for the injections while the start / start of the engine only to the operation necessary amount of fuel considered must become.

Farther it may be provided to divide the pilot injection so that one part before starting and another part when starting the engine is injected. Further divisions of fuel quantities or Multiple injections are also conceivable.

Of Further has an inventive pre-injection the advantage that possibly in the pressure accumulator or in the fuel system existing air or air bubbles from the fuel system with the pre-injection be blown out. When starting the engine is thus the fuel system bubble-free and the pressure build-up in particular at high pressure systems much faster, because no residual air is compressed must become.

The so far made statements while essentially referring to a high pressure fuel system, but are also readily transferable to a low-pressure fuel system.

In A low-pressure fuel system is usually on a second Dispensed fuel pump, so that the pressure alone by a first fuel pump is built. The pre-injection takes place then in a similar manner, but at the start then no further fuel pump is connected. Another fuel pressure increase during the Starts or in operation is conceivable.

By the procedure according to the invention is sufficient it advantageously, the fuel injection system in particular the injectors and fuel pumps / pumps for the maximum fuel flow, the for required operation in full load is to interpret. The additional fuel requirements are then in the starting phase by the procedure according to the invention to disposal posed.

Furthermore, it can be provided, at least during the starting phase, the pressure in the pressure accumulator 30 to determine and to measure the duration of the injection based on the existing pressure. It may also be provided to start with the pre-injection only from the presence of a certain fuel pressure.

Farther it may be provided, the first fuel pump for a given Duration to operate, taking after this period, even without investigation the fuel pressure, it is assumed that sufficient Fuel pressure is present, in which case an advance injection according to the invention then takes place.

It However, it can also be provided that the pre-start phase only begins, when the fuel pressure exceeds a minimum pressure or a first threshold.

If the position of the cylinders and the corresponding power strokes already at standstill or after a small crankshaft rotation of the internal combustion engine are known - for example. About absolute encoder on the crankshaft or camshaft - so it can be provided only in one or two combustion chambers to inject fuel in advance during the subsequent start the internal combustion engine is first ignited.

The Position of the crankshaft at the start can, for example, also known be if after stopping the engine the last Position of the crankshaft is held. It should be ensured though be that after that only the angular position of the crankshaft immaterial changes.

Farther can it be provided that based on input variables such for example, the ambient temperature, the engine temperature and / or oil temperature or other sizes one Pre-injection quantity or an injection strategy is determined. In particular, it can be provided between a cold start, Restart or warm start to distinguish.

Claims (12)

A method for starting an internal combustion engine with a direct fuel injection, in which an ignition and the direct fuel injection are operated with start parameters at a start of the internal combustion engine, characterized in that prior to this start in the presence of a start request, the ignition and the direct fuel injection with Pre-start parameters are operated. A method according to claim 1, characterized in that the pre-start parameters for the ignition are selected such that no or substantially no combustion of a fuel located in the combustion chamber takes place. Method according to claim 1 or 2, characterized that the pre-startup parameters for the direct fuel injection are chosen such that fuel is independent of Recognition of working cycles of cylinders an injection in at least one of the combustion chambers the internal combustion engine takes place. Method for starting an internal combustion engine with a direct fuel injection, wherein work cycles of the internal combustion engine are determined, thereby in that in the presence of a start request, first in sequence the power strokes injected directly into the combustion chambers of the cylinder will, with no ignition done or the ignition such that essentially no combustion takes place, and Subsequently, a start of the internal combustion engine is initiated. Method according to at least one of the preceding Claims, characterized in that a first fuel pump at the latest when a start request is put into operation. Method according to at least one of the preceding Claims, characterized in that a start request is considered first, when a fuel pressure exceeded a first pressure threshold Has. Method according to at least one of the preceding Claims, characterized in that the fuel pressure through a second Fuel pump increased becomes. Method according to at least one of the preceding Claims, characterized in that the start of the internal combustion engine is initiated, when the fuel pressure exceeds a second pressure threshold. Method according to at least one of the preceding Claims, characterized in that the fuel is injected without that a synchronization is made. Method according to at least one of the preceding Claims, characterized in that the amount of fuel at least in dependence of a Temperature is determined. Method according to at least one of the preceding Claims, characterized in that a first fuel pump upon actuation of a vehicle door in operation goes. control unit for operating an internal combustion engine, wherein the internal combustion engine at least one ignition and includes direct fuel injection, characterized, that the controller before a start of the internal combustion engine and in the presence of a start request in dependence of detected pre-star parameters the ignition and the direct fuel injection operates.