EP1122418B1 - Method for adaptation of maximum injection pressure in high pressure accumulator - Google Patents

Description

State of the art

The present invention relates to a method for Adaptation of one in a high pressure accumulator A direct injection fuel metering system Internal combustion engine prevailing maximum injection pressure, several of the high-pressure accumulators Controllable injectors depending on the operating size Metering fuel from the high pressure accumulator in Branch off the combustion chambers of the internal combustion engine.

The fuel metering system is, for example, as a common rail gasoline direct injection system with a pre-feed pump and a demand-driven or demand-controlled one High pressure pump trained. The present invention can but also with direct-injection diesel engines be used. The pre-feed pump is designed, for example, as an electric fuel pump and feeds fuel from a fuel reservoir into a low pressure area of the fuel metering system. By doing Low pressure range there is a pre-pressure of 4 bar, for example. The high pressure pump delivers the fuel from the Low pressure area in the high pressure accumulator in one High pressure area of the fuel metering system. By doing High pressure accumulator is dependent on the operating state of the Internal combustion engine a pressure between about 50 and 120 bar regulated. The branches of the high pressure accumulator depending on the operating size controllable injectors with appropriate control the fuel from the High pressure accumulator with the injection pressure there inject into the combustion chambers of the internal combustion engine.

DE 19 626 689 describes means for controlling the pressure a high pressure accumulator known.

The high pressure injectors of a fuel metering system open a direct-injection gasoline engine after activation by magnetic force. The magnetic force is generated by an electromagnet that is part of the Injector is. Is not activated the injector closed; a sealing element of the Injector is placed on a spring element Valve seat pressed. When opening the injector the sealing element by the magnetic force of the electromagnet lifted off the valve seat. The spring force of the Spring element and the hydraulic force in the High pressure accumulator prevailing injection pressure overcome become. To achieve such a large magnetic force can, the electromagnet is in practice with voltages operated that are significantly higher than that The battery voltage of the vehicle battery is (so-called booster mode).

Due to manufacturing tolerances or due to a Wear on the injection valves can lead to the fact that the magnetic force generated by the electromagnet is not sufficient, the spring force and the hydraulic force to overcome maximum injection pressure, and that Injector remains closed despite being activated. The is the case, for example, if between the moving mechanical Parts of the injector experience increased friction where in addition to opening the injector Spring force and the hydraulic force Frictional force has to be overcome. It can also be due to of manufacturing tolerances and wear of the parts of the fuel metering system, which the injection pressure in the Control or regulating high pressure accumulators, to an increase in Injection pressure come in the high pressure accumulator. Also in In such a case, the magnetic force of the Electromagnets often fail to deliver hydraulic power and overcome the spring force, and the injector remains closed despite activation. After all it is also conceivable that the injection valve during the booster operation opens briefly in the following Phase of the lower holding current falls again. A defiance Activation of the closed injection valve leads to Misfires and thus to a non-circular run Internal combustion engine and deteriorated Exhaust gas behavior of the internal combustion engine.

To avoid this problem despite not opening Solving injectors can be the maximum Injection pressure to which is regulated in the High pressure accumulator can be reduced so far that under Taking into account all manufacturing tolerances and the Wear of the injection valves with all injection valves Open security and throughout the given Keep injection duration open. With such a set injection pressure can save the resources of a However, the fuel metering system is not optimally used become.

It is therefore the object of the present invention maximum injection pressure in a high pressure accumulator direct-injection gasoline engine such adjust that on the one hand all injectors of the Open the fuel metering system with certainty and on the other hand, the resources of the fuel metering system can be optimally used.

• Einstellen eines bestimmten Einspritzdrucks als Anfangsdruck;
• Erhöhen des Einspritzdrucks ausgehend von dem Anfangsdruck bei gleichzeitigem Überprüfen, ob die Einspritzventile öffnen;
• Beenden der Erhöhung des Einspritzdrucks, sobald mindestens eines der Einspritzventile nicht mehr öffnet;
• Verringern des Einspritzdrucks um einen vorgegebenen Betrag; und
• Heranziehen des verringerten Einspritzdrucks als maximalen Einspritzdruck des Hochdruckspeichers.

To achieve this object, the invention proposes the following steps, starting from the method for adapting a maximum injection pressure of the type mentioned at the beginning:

• Setting a certain injection pressure as the initial pressure;
• Increasing the injection pressure from the initial pressure while checking whether the injectors open;
• Ceasing to increase the injection pressure as soon as at least one of the injection valves no longer opens;
• Reducing the injection pressure by a predetermined amount; and
• Using the reduced injection pressure as the maximum injection pressure of the high-pressure accumulator.

Advantages of the invention

The initial pressure at which the injection pressure in the High-pressure accumulator at the beginning of the invention Procedure is set, for example corresponds to Injection pressure, which according to the prior art in the High pressure accumulator is set. The initial pressure can selected the same size for internal combustion engines of the same type become. If there is any in the high pressure accumulator Initial pressure is an optimal use of resources of the fuel metering system is not possible.

Starting from this initial pressure, the injection pressure becomes in the high pressure accumulator in the operating points where the maximum injection pressure is required increased. The The pressure is preferably increased continuously. simultaneously it is checked whether the injection valves open. As long as open all the injectors, the injection pressure further increased.

However, as soon as at least one of the injectors fails opens, the injection pressure no longer increases elevated. Based on the achieved at that time Injection pressure then becomes one predetermined amount decreased. The default amount is chosen so that at the reduced injection pressure all Open injectors. It is also conceivable that the Injection pressure based on the injection pressure reached is slowly reduced until all the injectors again to open. In this case, the predetermined amount would be variable. The reduced injection pressure will eventually as the maximum injection pressure of the high-pressure accumulator used.

With the aid of the method according to the invention, the maximum injection pressure in the high pressure accumulator on the one hand be chosen so low that all injectors are still open the fuel metering system with certainty. On the other hand, the injection pressure is chosen so high that optimal use of the resources of the Fuel metering system is guaranteed.

With the method according to the invention, the maximum Injection pressure of the high pressure accumulator for each one Customized fuel metering system. This allows also manufacturing tolerances and wear of the Injectors in every fuel metering system be considered individually. So for everyone single internal combustion engine smooth running Internal combustion engine and a consistently good one Emission behavior while using the full Resources of the fuel metering system are guaranteed.

According to an advantageous development of the invention suggested that the initial pressure be set in this way will that considering all Manufacturing tolerances and wear of the Injectors all injectors with certainty to open. Should the implementation of the the method according to the invention nevertheless terminate the case, that at least one of the injectors in the Initial pressure does not open, so this injector, the fuel metering system or the whole Internal combustion engine classified as faulty and repaired or replaced.

According to a preferred embodiment of the present Invention it is proposed that a message be issued if the maximum injection pressure of the High pressure storage below a predeterminable Pressure threshold. According to this embodiment So a message is issued if the adapted maximum Injection pressure above the initial pressure but below a predefinable pressure threshold. This message can either a control unit of an internal combustion engine Further processing can be supplied. Or the message becomes an outside person for further processing or to initiate appropriate steps. The Message can be, for example, as an optical or acoustic Error message or as a display of adapt maximum injection pressure.

The process according to the invention is advantageously carried out according to assembly or repair, especially after Exchange of at least one injector, the Fuel metering system performed. One of external signal a special operating state force the internal combustion engine in which z. B. idle maximum injection pressure is required and the adaptation once, regardless of the operating point.

Alternatively, it is proposed that the method be predefined time intervals, especially after a specifiable Number of driving cycles or after a specifiable one Operating time. The maximum injection pressure is dependent on aging and wear Changes in the injectors and / or changes in pressure-controlling or pressure-regulating parts of the Fuel metering system set. The changes are made with such a large time constant that an adaptation of the maximum injection pressure in relatively large temporal Intervals, for example monthly, is completely sufficient.

According to a further preferred embodiment of the The present invention proposes that Procedure is carried out at the end of the line.

drawings

Figur 1

ein Ablaufdiagramm eines erfindungsgemäßen Verfahrens gemäß einer bevorzugten Ausführungsform.

A preferred embodiment of the present invention is explained below with reference to the drawings. It shows:

Figure 1

a flowchart of a method according to the invention according to a preferred embodiment.

The inventive method shown in Figure 1 is used to adapt one in a high pressure accumulator Fuel metering system of a direct-injection gasoline engine prevailing maximum injection pressure. Several branches of the high-pressure accumulator Controllable injectors depending on the operating size for metering fuel from the high pressure accumulator in Combustion chambers of the internal combustion engine serve.

The method according to the invention is carried out when the internal combustion engine is in an operating state, in which the maximum injection pressure is required. The The procedure begins in function block 1. In a subsequent function block 2 becomes a specific one Injection pressure as the initial pressure in the high pressure accumulator certainly. The initial pressure is determined such that under Taking into account all manufacturing tolerances and the Wear of the injection valves with all injection valves Open security.

In a subsequent function block 3, a targeted requirement, for example by a workshop that Initial pressure set in the high pressure accumulator. Alternatively, you can branch to a waiting loop in which it is checked whether the current Operating state of the internal combustion engine a maximum Injection pressure required. The queue is exited as soon as the internal combustion engine is in an operating state in which the maximum injection pressure is required.

It is then checked in a query block 4 whether in the injection pressure set in the high pressure accumulator all Open injectors. If all injectors open, the injection pressure is in a function block 5 increased by an increment in the high pressure accumulator. It is then checked again in the query block 4, whether all injectors open. The injection pressure will as long as incremented, or the loop consisting of the query block 4 and the function block 5 is run through until at least one of the Injector no longer opens.

Then starting from the query block 4 becomes a Function block 6 branches where the injection pressure in the High pressure accumulator is reduced by one increment. to Security is still in a subsequent query block 7 once checked whether all injectors again to open. If not, it becomes the function block 6 branches where the injection pressure again by one Increment is decreased. The loop consisting of the Function block 6 and the query block 7 will last run until all injectors open again. Then is branched into a function block 8, where the now in the injection pressure set as the high pressure accumulator maximum injection pressure of the high pressure accumulator is used. In a final function block 9 the method according to the invention has ended. Furthermore the procedure is always ended when the Injection pressure in the high pressure accumulator due to the Operating state of the internal combustion engine the maximum Leaves print area.

The method according to the invention can be installed after the Internal combustion engine at the end of the line or after repair, especially after replacing at least one Injector, the fuel metering system or Internal combustion engine to be run. Alternatively, it can Procedures but also at predefinable time intervals especially after a predeterminable number of driving cycles or after a predefinable operating time become.

Claims (8)

1. Method for operating a direct-injection internal combustion engine, the internal combustion engine having a fuel metering system with a high-pressure reservoir and a plurality of injection valves, which branch off from the high-pressure reservoir and can be controlled as a function of operating variables, for metering fuel from the high-pressure reservoir into combustion chambers of the internal combustion engine, and the injection valves being acted on in the closing direction by fuel present in the high-pressure reservoir at an injection pressure, characterized in that a maximum injection pressure prevailing in the high-pressure reservoir is adapted at predeterminable instants by performing the following steps:

   setting a specific injection pressure as initial pressure;

   increasing the injection pressure starting from the initial pressure, with simultaneous monitoring as to whether the injection valves open;

   terminating the increase in the injection pressure as soon as at least one of the injection valves no longer opens;

   reducing the injection pressure by a predetermined amount; and

   using the reduced injection pressure as the maximum injection pressure of the high-pressure reservoir.
2. Method according to Claim 1, characterized in that the initial pressure is set in such a way that, taking into account all manufacturing tolerances and the wear to the injection valves, all the injection valves reliably open and remain open during the entire predetermined injection duration.
3. Method according to Claim 1 or 2, characterized in that a message is output if the maximum injection pressure of the high-pressure reservoir lies below a predeterminable pressure threshold.
4. Method according to one of Claims 1 to 3, characterized in that the method is carried out after the assembly or the repair, in particular after the exchange of at least one injection valve, of the fuel metering system.
5. Method according to one of Claims 1 to 4, characterized in that the method is carried out at predeterminable temporal intervals.
6. Method according to Claim 5, characterized in that the method is carried out after a predeterminable number of driving cycles or after a predeterminable operating duration.
7. Method according to Claim 4, characterized in that the method is carried out at the end of the production line.
8. Method according to one of Claims 1 to 7, characterized in that the method is carried out at an operating point of the internal combustion engine at which the maximum injection pressure is demanded.

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