EP1611345A1

EP1611345A1 - Vacuum rinsing of an injector for internal combustion engines

Info

Publication number: EP1611345A1
Application number: EP03753329A
Authority: EP
Inventors: Klaus Balling
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-03-30
Filing date: 2003-09-29
Publication date: 2006-01-04
Also published as: DE10314454A1; US20060213485A1; DE10314454B4; WO2004088125A1; JP2006514212A

Abstract

The invention relates to a method for preparing for use a fuel injection valve for an internal combustion engine, for example for a system of common rail injectors which is at least partially filled with air at a starting moment and is supplied with a liquid substance by means of a connection normally used for fuel supply. The inventive method is characterised in that the internal chamber of the injection valve is brought to a pressure which is lower that the operation pressure in such a way that air bubbles increase the volume thereof with respect to a regular operation volume, and the substance inside the chamber is evacuated at a substantially constant low pressure, said method can be selectively repeated. Said method makes it possible to quickly prepare the injector for operation, notwithstanding the presence of a gaseous air in the liquid substance at the beginning of the process. A corresponding device is also disclosed.

Description

Vacuum flushing an injector for internal combustion engines

The invention relates to a method according to the preamble of claim 1. The invention is particularly important in the case of common rail injectors. Such an injector, which itself does not cause an increase in pressure, but is supplied directly with the fuel which is under pressure to be injected into the engine, in particular a diesel engine, reacts sensitively to air components in the medium processed by the injector. In the case of a ready-to-use diesel engine, this medium is diesel fuel, whereas the test medium used to measure and test the injector in the test field is usually not diesel fuel, but a hydraulically similar material that is preferably non-combustible. Air pockets in the injector, which are used when filling Medium are available before start-up, must over the volume flow of the return flow of the medium, which during normal operation z. B. results from leakage quantities and / or from the actuation of a control valve to be flushed out to a low pressure connection (leakage connection) of the injector.

The gaseous air has a much greater compressibility than the liquid medium, and as a result the dynamic damping behavior in the injector, in particular in a solenoid valve, is influenced in an unreproducible manner and has a direct effect on the injection quantity. This makes measurements in the test field more difficult. In a ready-to-use vehicle with a diesel engine, for example in which an injector has just been replaced in the workshop and is being filled with diesel fuel for the first time, the existing gaseous air also leads to unreproducible injection processes, which for a short time results in an uncomfortable driving experience and non-compliance with the required exhaust gas values may have. Dissolved air contained in the medium is not considered to be a nuisance in the present application as long as the air remains dissolved during the entire operating state of the injector and does not become gaseous.

The solenoid valve mentioned can be, in particular, a control valve which uses an outflow throttle to discharge medium from a

Control chamber of a stroke-controlled injector releases to initiate an injection process and locks to end the injection process. Various movable and immovable parts of the solenoid valve (see, for example, Fig. 2: armature, at least one spring, closure element to be actuated to release the outflow; immobile guidance of the armature) are arranged in a functional space. The named functional space and the parts of the control valve contained in it have numerous edges and projections which tend to hold air bubbles, provided they do not exceed a certain size, so that it takes considerable time (many seconds to about 1 minute) in normal operation can last until this functional space contains so little air in the gaseous state that there is practically no interference with the function of the internal combustion engine or during the measurement. The functional space is generally directly connected to a low-pressure connection of the injector, that is to say without the interposition of special shut-off elements. When the injector is operated at ambient pressure, which is simplistically regarded as 1 bar (absolute) or 0 bar (relative), in internal combustion engines, at least a slight overpressure (for example 0.5 bar) compared to the ambient pressure is often maintained at the low-pressure connection in order to To prevent drain lines from draining. There are internal combustion systems in which there is a considerably greater pressure (for example 10 bar) at the low-pressure connection of the injector, for example injectors, the control valve of which is actuated by a piezo actuator, preferably via a hydraulic coupler. Even with such an injector, it can be advantageous to make it air-free with the invention.

The invention has for its object to bring about the operational readiness of the injector despite the gaseous air contained therein in the liquid medium, that is to say with a pneumatic / hydraulic filling of the injector.

Advantages of the invention

The features of the method according to the invention described in claim 1 have the effect that the gaseous air forms air bubbles which are so large that they cannot get caught on projections of any kind in the injector because of the pressure drop. As a result, the air is removed as far as possible, and a clearly reproducible filling state of the injector is quickly achieved when testing in the test field or when operating in a motor vehicle.

The pressure drop should not be so great that the vapor pressure of the liquid medium or of parts thereof is reached or fallen below. The rapid discharge of the return quantity enriched with gas bubbles can be accelerated by flushing away with an air-free medium at a pressure which is considerably lower than that of the common rail pressure. In the motor vehicle, this medium can be fuel originating directly from the fuel tank. The device according to the invention according to claim 4 has devices for connecting an injector to a source of high pressure of the medium and to a vacuum connection. A control device with control connections of switching valves is advantageously coupled and further advantageously with a control circuit for opening and closing the injection openings of the injector.

drawing

A preferred embodiment of an arrangement with which an embodiment of a method according to the invention can be carried out is shown schematically in the drawing and is explained in more detail in the following description. Show it:

Fig. 1 is a hydraulic block diagram of the arrangement for removing

Air inclusions from a common rail injector, this arrangement being used both in the test field when the injection system is commissioned for the first time by the automobile manufacturer, or in a well-equipped repair shop for automotive engineering,

Fig. 2 shows a longitudinal section through a known stroke-controlled injector for diesel fuel with a solenoid valve, the pressure in a control chamber for actuating a valve piston via an outlet throttle

Controls opening and closing of injection ports; and ■

Fig. 3 is a timing diagram of the control of the valves V1 to V4.

Description of the embodiment

The arrangement 1 shown in FIG. 1 schematically shows an injector 2 mounted in the arrangement for common rail operation with a high pressure connection 3 for the liquid test medium that is free of gaseous air. This can be supplied from a connection 5, at which the test medium is available under high pressure, via a pipeline 6. The injector 2 has been used in the test field in the completely empty state, that is to say only filled with air, in the arrangement 1 shown, or else with mixed filling (air and test medium), for. B. in repeat tests.

In the example, the injector has a connection 7 for electrically actuating a magnetic control valve 8, which when actuated via an outlet throttle 9 reduces the pressure in a control chamber 10 (FIG. 2) in order to control the opening of injection openings 11 by means of a valve piston 12.

Leakage quantities, depending on the design of the injector, also a larger return flow quantity of the injector, which occurs during operation, flow out via a connection 13 (low-pressure connection, leakage connection) of the injector. In the example, this connection is not directly connected to a pipeline, for example, for returning it to the fuel tank, but to an adaptation head 14, which makes it possible to connect the connection 13 to other connections of the arrangement.

These include a vacuum pump 16, which is connected via a pipe 17 and a pipe branch 18 to a pipe 19 connected to the adaptation head; in addition, a container 20 for receiving the above-mentioned return flow quantity, which is connected to the pipe branch 18 via a pipeline 21. Furthermore, a low-pressure connection 22 for a low-pressure medium, here referred to as flushing medium, is provided, which is fed via a pipe 24 and a throttle 25 to a connection of the adaptation head 14 opposite the pipe 19. As a result, the rinsing medium can rinse out air bubbles 30 that reach the adaptation head 14 from the injector 2 in the direction to the left in the drawing. The function of the whole arrangement is controlled by switching valves, namely a switching valve V1 in line 17, a switching valve V2 in line 24, a switching valve V3 in line 21 and a switching valve V4 in line 6. Electrical control connections of the switching valves are included connected to a control device that controls the execution of the method. The functional sequence is explained on the basis of the curve profiles shown in FIG. 3, which designate the closed line with their base line and the open state of the assigned switching valve with their line running above the base line.

Initially, all switching valves V1 to V4 are blocked. Then the switching valves V1 and V4 are opened, that is to say vacuum is applied to the arrangement, and at the same time medium is fed to the port 3 of the injector 2 under the high pressure (for example 1600 bar in a conventional injector).

The negative pressure generated by the vacuum pump 16 acts via the adaptation head 14 at the connection 13 of the injector and also on its hydraulic internal volume, insofar as it is connected to the connection 13, in particular on the space in which the control valve is located. At the same time, the vacuum sucks the test medium out of the injector via the pipelines 17 and 19, the adapter head 14 and the connection 13, although there may be a lot of air that is not present in the form of bubbles in the first process. Any air bubbles originally present have increased due to the vacuum compared to the original state (when the pressure is reduced, for example, doubled in diameter from 1 bar to 0.1 bar) and can no longer get caught on any projections so easily they are flushed out by the constant return flow produced by the injector.

A control signal is fed to the electrical connection 7 via a control circuit 7 'coupled to the control device mentioned, which controls the injector in the example in the manner customary for the operation of an internal combustion engine, in the example with 1000 electrical pulses per minute, so that the control valve 8 per minute 1000 opening and closing operations. (This is much faster than, for example, the switching frequency of the control valve 2.) During this time, leakage fluid and control fluid, which arises when the valve piston 12 is lifted, flows out through the connection 13 and, due to the negative pressure present in the area of the control valve, rinses air bubbles which are enlarged compared to normal operation. The rinsed air bubbles get into the adapter head 14 and are there at one preferred embodiment of the method is flushed out of the adaptation head by flushing medium which is released a total of 3 times by the valve V2 in the example shown, which supports the removal of air from the vicinity of the injector.

For the purpose of simple handling of the system, the vacuum pump 16 is designed such that it sucks off both air and the medium or fuel that is produced. In other embodiments of the method and the device, the vacuum pump 16 only sucks in air; the mixture of air bubbles and liquid medium flowing vertically upwards through line 17 in the example, still under vacuum, arrives from above into a collecting container, where the liquid medium collects, and the vacuum pump is connected above the collecting container and therefore does not come in contact with the liquid medium. The collecting container mentioned must be emptied from time to time.

After the arrangement 1 described, as just described, was in operation for a few seconds, for example, the switching valve V1 (vacuum) has now been closed again. In the example, this is followed by a single rinsing process. The high pressure supply with test medium via the switching valve V4 is still maintained and the switching valve V3 is opened so that the

Low-pressure connection 13 of the injector 2, which is now still sufficiently air-free, is supplied to the collecting container 20 through the valve V4, as is provided in normal operation in the motor vehicle, and can be measured (quantified) as required when the medium is further supplied to the high-pressure connection 3.

Following the timing of the valve activity described here, a measurement of the properties of the injector can now be carried out in the test field, or it is now air-free in a combustion injection valve freshly used in an internal combustion engine and the arrangement of the internal combustion engine used to make it air-free can be made according to it Shutdown are removed and standard connections of the internal combustion engine, which had to be disconnected to attach the measuring device, are restored. In FIG. 1, measuring devices or measuring points for the vacuum, the low-pressure flushing medium and the high-pressure test medium symbolized as pointer instruments are also provided, by means of which the activity of the system can be monitored and the measured values of which can be recorded in a log.

At the times t1 to t6 shown in FIG. 3, of which t1 is shortly after the valves V1 and V4 are opened, and t6 is shortly after the close of V1, but the valve V2 is still open (liquid-conducting), and the rest The respective absolute pressures prevail in the area of the low pressure connection 13 of the injector 2 and associated relative sizes of the individual air bubbles in the area of the control valve 8, expressed as volumes:

t1: absolute pressure 0.1 bar, air bubble volume 10; t2: absolute pressure 2.6 bar, air bubble volume 0.38; t3: absolute pressure 0.1 bar, air bubble volume 10 t4: absolute pressure 2.6 bar, air bubble volume 0.38; t5: absolute pressure 0.1 bar, air bubble volume 10; t6: absolute pressure 4 bar, air bubble volume 0.25.

FIG. 3 is only to be understood as an illustration, in practice more rinsing processes (or not a single rinsing process) and several repetitions of the process shown can be carried out.

When carrying out the method according to the invention and when the device according to the invention is operating, there is a steady decrease because new, air-free medium is always supplied to the connection 3, the number and in particular the total volume of the air bubbles present in the injector and after a short time, in any case after a few seconds the injector practically free of air and measurements can now be carried out precisely on the injector.

If the arrangement 1 z. B. used in a specialist company in automotive engineering, for example to install a renewed and thus still air-filled injector on an internal combustion engine, it is therefore only necessary to connect the system parts described above to the injector, that is to say the adaptation head, and with this the vacuum pump. The supply of high pressure medium, namely in this case diesel fuel, is already available on the motor vehicle side without any special measures. In this case, it may be difficult to provide a low-pressure flushing medium, namely also diesel fuel. In this case, the adapter head for use in the specialist workshop would not have a connection for flushing medium, or this connection would be closed.

It may be appropriate to use other injectors, e.g. those which bring fuel from a relatively low pressure to the injection pressure via a built-in compressor, according to the invention to free air pockets.

It is assumed that the influence of air bubbles in a solenoid valve, as just explained, is particularly disruptive because, for example, a delay in the opening movement of the armature of the solenoid valve or a faster opening movement as a result of air pockets compared to the desired state leads to a delayed or accelerated increase in the leads to magnetic force acting on the armature, so that the influence on the function of the solenoid valve is particularly strong.

The invention can also be applied to other types of control valves with utility, particularly for example a control valve actuated by a piezo actuator, although due to the lack of the above-mentioned positive feedback effect on the electromagnetic valve, the latter may not be as strongly affected by the presence of air bubbles is influenced in its function. In both types of valve mentioned, it may be particularly disruptive that, after starting up a largely air-filled injection valve, foaming can initially occur in the area in which the moving parts of the control valve are located, making measurement difficult or impossible. Such injectors, which require the presence of a hydraulic ^'coupler a counter-holding pressure at the leakage connection of, for example 10 bar during normal operation can, freed in the manner described here of entrapped air and are usually exposed to the mentioned low pressure of 0.1 bar, which is not used for very long.

Claims

claims

1. Method for preparing an injection valve for an internal combustion engine, for. B. a common rail injector, which is initially at least partially filled with air during commissioning and to which a liquid medium is supplied via a connection customary for the fuel supply, characterized in that an interior of the injection valve has a ■ • compared to the normal Operation brought reduced pressure, such that existing air bubbles increase in volume compared to their volume during normal operation, and that the medium contained in said interior is flushed out under at least approximately constant reduced pressure, optionally with several repetitions of the process.

2. The method according to claim 1, characterized in that control signals for opening and closing the injection valve are supplied to the injection valve.

3. The method according to claim 1 or 2, characterized in that the flushing out of the medium after leaving the injection valve is supported by supplying a low-pressure medium.

4. Device for performing the method according to one of the preceding claims, characterized in that the device comprises:

an adaptation head (14) to be connected to a low pressure connection or leakage connection of the injection valve (2), which can be connected to a vacuum pump (16) and that a device for supplying medium under high pressure to a connection of the injection valve provided for this purpose is provided.

5. The device according to claim 4, characterized in that the adaptation head (14) has a connection with a low pressure connection for flushing medium in connection.

6. The device according to claim 4 or 5, characterized in that a return tank (20) for the return amount with the adaptation head (14) is connected.

7. Device according to one of claims 4 to 6, characterized in that at least one switching valve (V1, V2, V3, V4) for controlling temporal processes of the. _,

Device is present.

8. The device according to claim 7, characterized in that it has a control device which is connected to a control connection of the at least one switching valve (V1, V2, V3, V4).

9. The device according to claim 8, characterized in that the control device is coupled to an electrical connection of the injector.