WO2006008208A1

WO2006008208A1 - Electrovalve for an injector for common rail fuel injection systems, comprising a damping element

Info

Publication number: WO2006008208A1
Application number: PCT/EP2005/052501
Authority: WO
Inventors: Rainer Haeberer; Frieder Buerkle; Stephan Amelang; Anastasios Manoussopoulos
Original assignee: Robert Bosch Gmbh
Priority date: 2004-07-21
Filing date: 2005-06-01
Publication date: 2006-01-26
Also published as: TW200604432A; DE102004035291A1

Abstract

The invention relates to an electrovalve for an injector for a common rail fuel injection system, comprising a valve control system for opening and closing a nozzle. The aim of the invention is to compensate for pressure drops inside the injector (1), for example caused by air inclusion in the fuel to be injected. To this end, a damping element (15) is arranged between the electrovalve (8) and the electrovalve armature (9), said damping element exerting a damping force on the electrovalve armature (9) and thus on the nozzle needle (5).

Description

Solenoid valve for an injector for common rail fuel injection systems with damping element

The invention relates to a solenoid valve for an injector for a common rail injection system with a valve control for opening and closing a nozzle, wherein within the solenoid valve, a movably mounted solenoid valve armature is provided, which in turn with a valve spool and this in turn with a nozzle needle, which is arranged in the nozzle, is in connection düng.

State of the art

An injector is intended to inject high-pressure fuel in very small amounts into a combustion chamber of a fuel-fired engine. The injector consists of a control part and an injection part. Among other things, the control part comprises an inlet, which is provided for the fuel which leads into the injector and which is under high pressure. In addition, a solenoid valve is arranged in the control part, which essentially comprises a magnet valve armature and a coil surrounding the solenoid valve armature. The solenoid valve armature is held in a position corresponding to a spring. The solenoid valve anchor further comprises ei¬ NEN control valve seat, which corresponds to a throttle valve. The injection part of the injector comprises the valve control piston, which in turn communicates with the throttle valve and a nozzle needle which is arranged in a nozzle. The nozzle needle itself is also spring loaded.

In the idle state, the solenoid valve is not current-driven and therefore the solenoid valve armature is pressed in the direction of the nozzle due to the spring. Thus, the throttle valve is closed and the Ven¬ tilsteuerkolben presses against the nozzle needle, which in turn closes the nozzle itself.

In addition, the fuel pressure is continuously applied to the seat of the nozzle needle. In addition, the same pressure prevails on the control part above the valve control piston.

Due to the different cross-sectional area ratios of the valve spool and the nozzle needle, the entire resulting hydraulic force component acts in the closing direction.

As soon as the solenoid valve is energized, the solenoid valve armature is raised in the opening direction. As a result, it releases a very exactly tolerated and manufactured cross-section of the throttle valve in the control part, as a result of which the pressure acting on the valve control piston itself quickly breaks down. As a result, the nozzle needle is lifted off the seat and the injection process starts. This is limited by the interruption of the magnetic current.

Disadvantages of the prior art By pumping the fuel into the common rail

Injection system, it may happen that air is sucked in with the fuel, especially when using suction pumps.

In the high-pressure accumulator (common rail), the air is dissolved in the fuel. However, it enters the state that when the throttle valve is open fuel in the return device by significantly lower pressures are present, so that the corresponding air leaves the ge dissolved state. Thus, the distance traveled by the magnetic valve armature, as it is also flushed with fuel, can very much depend on how large the proportion of air in the fuel is.

The movement of the solenoid valve anchor and in particular the stop behavior in turn depends on the pressure environment. at

Air inclusions can therefore lead to unwanted and uncontrolled impact behavior, which in turn has the consequence that the opening times of the injector are subject to uncertainty and thus the injection quantities are not correctly defined.

Object of the invention

The object of the invention is to further develop an injector of the type present in such a way that the bouncing behavior caused by air entrapment, which is present in a fuel, is reduced by appropriate design of the injector.

Solution of the task The object is achieved in that within the control part of the injector between the solenoid valve and the solenoid valve armature, a damping element is arranged, which exerts a corresponding damping force.

Advantages of the invention

The damping element compensates for pressure drops in the valve control chamber and slight variations in pressure. The bounce behavior of the solenoid valve anchor is thereby predictable and adjustable by the choice of the damping parameters.

The dynamics of the movements of the solenoid valve anchor have a direct influence on the injection quantity of the fuel into the combustion chamber. If the solenoid valve armature makes a controlled movement, the fuel injection quantity is also controllable. For this reason, it is appropriate to use damping agents in this area.

This additional damping has a particularly great effect in two extreme ranges.

First, it has an influence on the movement of the solenoid valve anchor when opening the injector. If the solenoid valve arm moves without counter-pressure, the nozzle opens abruptly and it is immediately possible for a certain amount of fuel to flow into the combustion chamber. On the other hand, if the solenoid valve armature moves against a backpressure present in the valve control chamber, the nozzle is only gradually opened and initially only a small amount of fuel can flow into the combustion chamber. The amount gradually increases with the deflection of the solenoid valve armature and thus with the displacement of the valve spool.

For optimal combustion, an initially slower increase in fuel quantity is an advantage.

The other extreme region, in which the attenuation plays a special role, is the closing process of the injector.

If the loading of the solenoid valve armature is stopped with power, then the solenoid valve armature moves in the closing direction into its so-called equilibrium position. In this case, it is surrounded by fuel and is subject to the actual spring pressure and ei¬ nem hydraulic pressure. However, if air pockets are present in the fuel, the hydraulic equilibrium pressure drops and the solenoid valve bounces into its equilibrium position almost without resistance, which in turn leads to a so-called closing bounce behavior of the magnet valve with several oscillations again affects the opening and closing of the nozzle.

With each ringing, the injector is thus reopened and, even after the closing time fixed by the end of the energization, fuel can flow into the combustion chamber and thus considerably change the running properties of the fuel engine.

The additional damping element according to the invention, however, ensures that, regardless of the pressure conditions in the valve control chamber, there is a damped closing action of the solenoid valve armature comes. It is prevented that the solenoid valve armature carries out a prolonged oscillation after the end of the energization, without further fuel being able to flow into the combustion chamber.

In a preferred embodiment, the damping element is designed such that it has a spring and a defined mass. The damping force exerted by the damping element is generated in this case by the inertia of the mass and the Federkon¬ constant of the spring. By a suitable selection of these parameters, the corresponding damping force can be set such that the pressure fluctuations occurring in the valve control chamber are compensated accordingly.

Further advantageous embodiments will become apparent from the following descriptions, drawings and claims.

Drawings Show:

1 is a schematic representation of the injector in Ruhezu¬ stand;

FIG. 2 shows a schematic representation of the injector as in FIG. 1, but with respect to FIG. 1 in the injection state;

3 is an enlarged view of an embodiment of an injector according to the invention in section;

4 shows measurement curves in which the movement of the solenoid valve anchor as well as the injection rate of the fuel into the Combustion chamber of a fuel engine as a function of time are shown, on the one hand for an Injek¬ gate, is provided in the fuel with air trapped in the valve control room, once with Dämpfungsele¬ element and once without damping element.

Description of an embodiment

FIG. 1 shows an overall view of an injector 1 comprising a control part S and an injection part E. The fuel which is to be injected into the combustion chamber of a fuel-injection engine is supplied by a common-rail injection system (not shown) via a fuel supply line 2 , which is arranged on the control part S of the injector 1, guided via inlet channels 3 to the injection part E in the direction of the nozzle 4. The nozzle 4 itself is controlled via a nozzle needle 5, which in turn is connected to a valve control piston 6 and this, in turn, to a valve control chamber 7.

The valve control chamber 7, which is arranged in the control part S of the injector 1, comprises a solenoid valve 8 with a Magnetven¬ tilanker 9, the solenoid valve armature 9 provides a control valve seat 10 which corresponds in the state shown in Figure 1 with a throttle valve 11. The solenoid valve armature 9 is controlled by a coil 12.

Furthermore, a return line 13 for the fuel is provided in the control part S of the injector 1. When the coil 12 of the solenoid valve 8 is energized (FIG. 2), the solenoid valve armature 9 moves in the opening direction 14 and the corresponding throttle valve 11 is released so that fuel can flow via the inlet 3 in the direction of the nozzle 4 as well can flow into the valve control chamber 7 and the return line 13.

FIG. 3 shows a partial illustration of the embodiment according to the invention. In the control part S, a damping element 15 is arranged in the region of the magnet valve armature 9, which consists of a spring 16 and a mass disk 17. The damping element 15 is connected both to the solenoid valve armature 9 and to the solenoid valve 8, so that the solenoid valve armature 9, when moving in the closing direction 18 and in the opening direction 14, operates the damping force generated by the damping element 15.

The damping element 15 thus has a damping effect which corresponds to the hydraulic damping force of a solenoid valve umströ¬ ing in the figure not shown fuel.

In FIG. 4, the embodiment which has the design according to the invention of the magnetic valve 8 according to FIG. 3 is shown by means of measuring curves in comparison to the solutions shown in the prior art.

The measured curves show the so-called injection rate (amount of ein¬ injected fuel) in the ordinate right over the time shown. In the ordinate on the left, the deflection of the Magnetven¬ tilankers 9 is shown from its rest position. The sizes are arbitrary.

First, the negative deflection of the solenoid valve armature 9 is plotted from the closed position over time in the curve 101, if due to an air inclusion (here about 44%) in the fuel only low damping forces. The curve 101 points immediately after opening, which takes place at a time t = 0, so-called opening preheater 103. These arise because the magnet valve anchor 9 lifts off from its seat with little damping, causing it to vibrate.

After completion of the energization of the solenoid valve 8, the solenoid valve armature 9 does not return to the closed position in an over-damped motion, but executes a series of closing bounces, which are seen as strong deflections 104 of the curve 101.

In the curve 102, the negative deflection of the magnetic valve armature 9 from the closed position is plotted over time, in which case a damping is present.

This becomes clear, on the one hand, since the opening of the solenoid valve armature 9 (curve 106 of the course of the opening) runs much more slowly than in the unattenuated case and the closing process is quasi over-damped, so there are no discernible vibration outbreaks.

The corresponding injection rates of the fuel into the combustion chamber over time are plotted in curves 201 and 202. Curve 201 shows the injection rate for a solenoid valve armature 9 with virtually undamped motion, this curve 201 being comparable to the curve 101.

Curve 202 shows for a solenoid valve armature 9 a damped movement, comparable to curve 102. The rapid opening 103 of the un-damped magnet valve armature 9 leads to a rapid increase in the injection rate and the oscillations during closing (region 104) of the undamped magnet valve armature 9 result in a longer duration of the injection and thus in a higher Ein¬ injection rate when closing.

In comparison with the closing behavior of the damped solenoid valve armature 9, it can be seen that in the undamped case, the fuel can flow in for a certain period of time 206.

This period of time 206 is decisive for the difference in the amount of fuel flowed in, which results from the temporal integrals of the curves 201 and 202 for the fuel rate.

The damping element 15 introduced according to the invention thus leads to a smoothing of the curve 106 of the magnet valve armature 9. The injector 1 is insensitive to a higher Luftan¬ part, which is trapped in the fuel, although the hydaulic damping due to these air pockets reduced.

The construction according to the invention is very simple and effective and can be inserted without special configuration of the injector 1.

Claims

1. Solenoid valve for an injector for a common rail injection system with a valve control for opening and closing a nozzle, wherein within the solenoid valve, a movably mounted ge solenoid valve armature is provided via a throttle valve with a valve spool and this in turn with a Nozzle needle, which is arranged in the nozzle, is in communication, characterized in that between magnetic valve (8) and solenoid valve armature (9) a damping element (15) is arranged, which has a corresponding damping force on the solenoid valve armature (9) and thus the nozzle needle (5) exerts.

2. Solenoid valve according to claim 1, characterized in that the damping element (15) is a spring-mass element.

3. Solenoid valve according to at least one of claims 1 or 2, da¬ characterized in that the damping element (15) is arranged such an¬ that the solenoid valve armature (9) in the closing direction (18) operates against the damping force.

4. Solenoid valve according to at least one of claims 1 to 3, da¬ characterized _/ in that the damping element (15) is arranged such that the solenoid valve armature (9) in the opening direction (14) operates against the damping force.

5. Injector for a common rail injection system with a valve control for opening and closing a nozzle, characterized in that a solenoid valve (8) according to claim 1 and optionally according to at least one of claims 2 to 4 vor¬ seen is.