EP0914557B1 - Solenoid valve such as an impact solenoid valve for a hammer-effect fuel injection system in a motor vehicle - Google Patents

Abstract

A solenoid valve (1) having a fuel inlet (3) and a fuel outlet (4) and containing a solenoid coil (5) combined with power supply control means therefor, as well as a magnetic piece (6) and a plunger (7) with facing contact surfaces. The plunger (7) is connected to sealing means (8) for opening and closing said outlet (4) by moving the plunger (7) relative to the magnetic piece and causing mutual engagement between the contact surfaces thereof. Said solenoid coil power supply control means (5a) are arranged to apply a current (I) to said coil that has a surge phase (A) and a plateau phase (M). At the end of the surge phase, the current has a shallower slope (A2) than at the start (A1) thereof, whereby the impact of the plunger (7) against the magnetic piece (6) is reduced as the valve body outlet is opened.

Description

The present invention relates to a solenoid valve for example of impact for a fuel injection system by water hammer in a vehicle engine.

Pollution control standards as well that the energy savings imposed on the manufacturers of vehicles, have led them to develop different fuel injection systems in engines.

Among the different solutions developed, direct fuel injection into a engine combustion has a number of advantages, especially for two-stroke engines, in which the separation of oxidant and fuel allows to carry out the scanning phase without loss of the latter, unlike carburetor feed solutions for example.

This advantage leads to considerable gains in polluting emissions and in fuel consumption.

However, this requires injection systems capable of delivering quantities fuel variables at often high frequencies and this, with fuel atomization characteristics sufficient to ensure the start-up and running of combustion in the engine.

For example, in the context of so-called fuel reserve injection systems and electromagnetic injector, there is a trend general to increase the pressure in the reserve of fuel, upstream of the injector.

The energy required for such an increase pressure must be supplied by the engine itself or by an annexed energy source on board on board the vehicle if the application concerns a vehicle.

This extra energy needed is naturally a disadvantage, especially in the context of engines small displacements in which neither the engine nor its environment, only allow energy consumption important.

In addition, the use of injection systems synchronized with the engine, for example by camshaft, leads to significant variations in the appearance of the pressure in the injection system depending on the speed with a negative influence on the formation of the mixture and combustion in the engine.

It is for these different reasons that fuel injection systems based on a so-called effect water hammer have been developed in the state of technical.

This type of systems being well known in the state of the technique, we will not describe it in more detail by the following.

It will simply be noted that a so-called solenoid valve is connected to the fuel injector in the motor, to create by successive opening and closing of it, fuel pressure waves at the level of the injector.

This then allows direct injection of fuel in the engine combustion chamber.

Generally speaking, the solenoid valves and in particular impact solenoid valves for such systems, have a tubular valve body having at its ends, a fuel inlet and outlet and in which an electromagnet coil is arranged associated with a tubular magnetic piece and a core tubular plunger.

This magnetic part and this plunger core are arranged one in the extension of the other, in the recess of the electromagnet coil and the plunger core is connected to means for closing the outlet of the body valve to control the opening and closing of this in response to a command to power the solenoid coil, by axial displacement of the plunger core relative to the magnetic part, and coming to bear contact surfaces opposite this magnetic part and this plunger core.

Furthermore, means for guiding the movements the plunger core and elastic biasing means of the latter in the closed position of the shutter means are also planned.

Different embodiments of these solenoid valves have been described in the state of the art (see for example DD-105,653).

However, in the context of small displacement engines operating at high speeds, direct injection requires solenoid valves with performance extremely high.

1) le temps de réponse à l'ouverture et à la fermeture,

2) la fréquence de fonctionnement,

3) la durée de vie, et

4) la consommation énergétique.

The development criteria for these solenoid valves are indeed:

1) response time on opening and closing,

2) the operating frequency,

3) service life, and

4) energy consumption.

However, the solenoid valves known in the state of the art, do not meet these different criteria in a satisfying manner.

The object of the invention is therefore to solve these problems.

To this end, the invention relates to a solenoid valve for example of impact for an injection system of fuel by water hammer in a vehicle engine, of the type comprising a tubular valve body having at its ends, a fuel inlet and outlet, and in which is arranged a connected electromagnet coil to means for supplying it and associated with a tubular magnetic part and a tubular plunger core, arranged in the extension of one another in the recess of the electromagnet coil, and having facing contact surfaces, the plunger being connected to means for closing the outlet of the valve body for, in response to the excitation or not of the electromagnet coil under the control of the means of supply of this, open or close the valve body outlet, by axial displacement of the plunger with respect to the workpiece magnetic and coming into contact with their contact surfaces in the valve body outlet open position, and elastic biasing means of the plunger core in closed position of the valve body outlet, the means for controlling the supply of the electromagnet coil being adapted to apply current thereto presenting a call phase and a hold phase, the current at the end of the call phase with a reduced slope compared to that at the beginning of it, to reduce the impact of the plunger core on the magnetic part when opening the valve body outlet and therefore the risk of degradation of these parts, characterized in that during the holding phase, the current has a positive slope to compensate for the increase in hydrodynamic force exerted by the fuel on the plunger, as and when as its speed increases in the valve body.

• la Fig.1 représente une vue en coupe illustrant la structure générale d'un exemple de réalisation d'une électrovanne d'impact selon l'invention; et
• la Fig.2 illustre la forme d'un courant d'alimentation délivré par des moyens de commande à une bobine d'électro-aimant entrant dans la constitution de cette électrovanne.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which:

• Fig.1 shows a sectional view illustrating the general structure of an exemplary embodiment of an impact solenoid valve according to the invention; and
• Fig.2 illustrates the form of a supply current delivered by control means to a coil of electromagnet used in the constitution of this solenoid valve.

We recognize in fact in this figure 1, a solenoid valve designated by the general reference 1, which can be used as an impact solenoid valve for a system fuel injection by water hammer in a vehicle heat engine.

This type of fuel injection systems by water hammer effect being well known in the state of technical, we will not describe it in detail.

The solenoid valve according to the invention comprises conventionally, a tubular valve body designated by the general reference 2 having at its ends, a fuel inlet and outlet, respectively 3 and 4.

In this valve body there is a coil electromagnet designated by the general reference 5, this electromagnet coil being associated with a part tubular magnetic designated by the general reference 6 and a tubular plunger core designated by the reference general 7.

In addition, this electromagnet coil is connected to means for controlling its supply designated by the reference 5a in this figure 1.

The magnetic part 6 and the plunger core 7 are arranged one in the extension of the other, in the recess of the electromagnet coil between the input and the fuel outlet and the plunger core 7 is connected to means 8 for closing the outlet 4 of the body of valve 2, to control the opening and closing of this in response to a command to power the solenoid coil 5, by axial displacement of the core plunger 7 with respect to the magnetic part.

The sealing means may present different suitable forms known in the state of technical.

Note also that the output 4 of this body valve can be associated with a nozzle 9 having by example a flared recess, either in stages as is represented, either continuously.

Furthermore, means 10 for guiding the displacements of the plunger core 7 and the elastic means 11 for biasing this plunger core in the position of closure of the shutter means 8, are also provided.

The means 10 for guiding the movements of the plunger core include for example a sleeve tubular guide including a first end for example 10a extends into the magnetic part 6 and of which a second end for example l0 protrudes beyond this magnetic piece. The plunger core 7 is then placed on this second end 10b of the guide sleeve 10 and is therefore mounted movable to slide around this end of the guide sleeve.

Furthermore, the elastic means 11 of stress on this plunger core in the closed position from the valve body outlet, are also arranged in the recess thereof, in the extension of the guide sleeve between the second end of this and a corresponding abutment surface, by example 7a, of the plunger core.

It can be seen, for example, that these means elastic can include a spring for example helical arranged in the plunger core, in the extension of the guide sleeve, one end of this helical spring 11 bearing on the end the guide sleeve, while the other end of it is in abutment on the abutment surface 7a of the plunger core.

It can therefore be seen that when ordering the supply of the electromagnet coil 5, we cause the displacement of the plunger core 7 from the position of closure of the means for closing the outlet of this body valve, as illustrated in this figure, towards its open position by axial displacement of this core plunger on the corresponding end of the means of guide and more particularly of the guide sleeve.

This structure presents a number advantages, especially in terms of its simplicity of construction and operation.

Indeed, the guide means no longer form an obstacle to the magnetic flux lines of the coil electromagnet, as was the case in the state of the technique, which improves the magnetic efficiency from the whole.

In addition, the optimization of the layout guide means and elastic biasing means of the plunger also reduces the size of the solenoid valve and limit as much as possible the risks of blocking the plunger, while allowing it to operate at very high rates like those encountered in one of the applications previously mentioned, i.e. systems fuel injection into vehicle engines.

For this purpose, a fuel injector (not shown) can be connected via example of a line 12 at the solenoid valve, upstream of the sealing means, thanks to connection means any generally designated by reference 13 on the face.

In this solenoid valve structure, the part magnetic 6 and the plunger core 7 have surfaces contact respectively 6a, 7b opposite, adapted to come into contact with one another, when opening from the valve body outlet after the excitation of the electromagnet coil 5 by the control means 5a.

One or both of these contact surfaces have advantageously protruding and recessed parts which reduce the area of these bearing surfaces one against the other, when the plunger is in opening position of the valve body outlet.

In the embodiment shown on this figure 1, the corresponding surface 6a of the part magnetic 6 indeed has an annular shoulder continuous 6b.

This configuration reduces the forces residual between magnetic part 6 and the core plunger 7, which are relatively large, and this especially when the valve body closes, these residual forces limiting the generation of the fuel pressure and operating frequencies of this valve, by increasing the closing time of the solenoid valve.

We can then see that the configuration described reduces these forces while optimizing the air gap and therefore the energy consumption of this valve.

It goes without saying of course that different forms of these protruding and recessed parts of these surfaces of contact can be considered.

Furthermore, FIG. 2 shows, the shape of the average current I applied by the means of Sa control in the electromagnet coil 5 when excitation.

Conventionally, such a current has two phases, one called the call designated by the reference A on this figure, and the other so-called holding indicated by the reference M in this figure.

Such a form of current indeed makes it possible to create relatively attractive magnetic forces of the plunger core 7 during the detachment from it and then limit these forces to one level sufficient to hold the plunger core 7 against the magnetic part 6 in particular to achieve savings energy.

In the solenoid valve according to the invention, the current I, at the end of the call phase A presents a slope reduced compared to that of the beginning of this one, this which reduces the impact of the plunger core 7 on the magnetic piece 6 when opening the outlet of the valve body and therefore the risk of degradation of these rooms.

In the embodiment shown on this figure 2, this current I has indeed two slopes designated by A1 and A2 respectively in this figure, for the start and end of the call phase A thereof.

In fact, it can be seen that during phase A1, the current has a relatively steep slope, while that during phase A2, the current has a slope reduced compared to that of the first part of this phase.

Of course, other forms of slope current can be considered and this can by example present a gradually decreasing slope and continuously towards the end of this call phase.

During the maintenance phase M, the current I presents a positive slope and increases slightly for compensate for the increase in hydrodynamic force exerted by the fuel on the plunger, as and as the speed of the fuel in the body of valve increases.

Indeed, when opening the exit of the valve body, the fuel speed increases in this and the hydrodynamic force exerted by this fuel on the plunger core crossed by the fuel, therefore increases accordingly.

It is then advisable to gradually increase the holding current to maintain the shutter means in the valve body open position up to a value corresponding to the maximum fuel speed.

So the holding current does not stay constant at the required value corresponding to the speed maximum fuel for an opening period of the valve, which saves energy.

This form of current is obtained by control means having any structure for example classic programmable.

It is therefore understandable that in the solenoid valve according to the invention, the characteristics which have just been described about the contact surfaces of the part magnetic and the plunger and the excitation current of the electromagnet coil applied to it by the control means thereof, allow to optimize the operation of this solenoid valve and in particular its opening and closing response times, its operating frequency, service life and consumption in energy.

Claims (2)

1. Electromagnetic valve, for example of the impact type, for a hammer effect fuel injection system in a motor vehicle, of the type comprising a tubular valve body (2) having, at its ends, a fuel intake (3) and outlet (4), and in which is disposed an electromagnetic coil (5) connected to supply means (5a) therefor and associated with a tubular magnetic part (6) and a tubular plunger core (7), arranged in the extension of one another in the recess of the electromagnetic coil, and having opposing contact surfaces (6a, 7b), the plunger core (7) being connected to means (8) for blocking the outlet of the valve body (2) in order to open or close the outlet of the valve body in response to the excitation or non-excitation of the electromagnetic coil under the control of the supply means therefor, by axial displacement of the plunger core (7) relative to the magnetic part (6) and abutment of the contact surfaces (6a, 7b) of the latter in the open position of the outlet from the valve body, and means (11) for resiliently biasing the plunger core in the closed position of the outlet of the valve body, the means (5a) for controlling the supply to the electromagnetic coil (5) being adapted to apply to said coil a current (I) having an attracting phase (A) and a maintenance phase (M), the current at the end of the attracting phase having a reduced gradient (A2) compared with the gradient (A1) at the start thereof, to reduce the impact of the plunger core (7) on the magnetic part (6) when the outlet of the valve body is opened and hence to reduce the risk of damage to these parts, characterised in that during the maintenance phase (M) the current (I) has a positive gradient to compensate for the increase in the hydrodynamic force exerted by the fuel on the plunger core (7), as its speed increases in the valve body.
2. Electromagnetic valve according to claim 1, characterised in that at least one of the contact surfaces (6a, 7b) of the magnetic part (6) and/or the plunger core (7) comprises projecting and recessed portions so as to reduce the surface area of these surfaces abutting against one another when the plunger core (7) is in the open position of the outlet of the valve body.

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