WO2001045217A1

WO2001045217A1 - Spark electrode arrangement

Info

Publication number: WO2001045217A1
Application number: PCT/SE2000/002420
Authority: WO
Inventors: Karl Marforio; Alf Hedlund
Original assignee: Saab Automobile Ab
Priority date: 1999-12-15
Filing date: 2000-12-04
Publication date: 2001-06-21
Also published as: AU2240901A; SE9904597D0; SE9904597L

Abstract

In an ignition electrode arrangement for a cylinder in an internal combustion engine, for example an Otto engine, a first electrode (7) and a second electrode (8) interact with one another, the first electrode (7) being arranged on an ignition means (6) fastened in a cylinder head. The first electrode (7) is arranged movably in the ignition means (6) in order to make it possible to change the size of the spark gap. The size of the spark gap is controlled during operation by the ignition system of the engine.

Description

SPARK ELECTRODE ARRANGEMENT

Technical field

The invention relates to an ignition electrode arrangement for an internal combustion engine, according to the precharacterizing clause of Patent Claim 1, and to a method according to the precharacterizing clause of Patent Claim 12.

State of the art

In an internal combustion engine with spark ignition, use is normally made of an ignition electrode arrangement in which a positive electrode and an earth electrode are assembled in a sparking plug which is mounted removably in the cylinder head of the engine and has a fixed spark gap.

In order to achieve better combustion conditions in the case of inter alia low load, it is desirable to be able to use^' a larger spark gap than a conventional sparking plug allows, and the use has therefore been proposed of an ignition electrode arrangement in which the sparking plug has only a positive electrode and the earth electrode is arranged on the piston of the cylinder. By selecting a suitable ignition time, it is in this way possible to obtain the desired electrode distance. However, a disadvantage is that, with a large spark gap, it is not always possible to produce a satisfactory spark because, for practical reasons, the ignition voltage has to be limited and is therefore not always adequate. In this connection, there is a risk that the spark will, instead of striking the piston, strike the cylinder head close to the sparking plug, with various disadvantages as a consequence. In order to achieve a larger spark gap than with a conventional sparking plug, positioning a fixed earth electrode on the cylinder head has also been tried instead of having an earth electrode on the sparking plug. However, this solution does not allow the size of the spark gap to be changed, which is possible when the earth electrode is positioned on the piston-.

The object of the invention One object of the invention is to produce an improved ignition electrode arrangement. Another object is to make possible improved spark control and in this way improved combustion control .

Summary of the invention

These objects are achieved by means of an ignition electrode arrangement having the features indicated in Patent Claim 1 and by a method having the features indicated in Patent Claim 12. By making the first electrode movable, a possibility is afforded for controlling the size of the spark gap. By furthermore controlling the size of the spark gap as a function of the current operating situation, it is possible to produce an optimum ignition spark' for the current operating situation, which in turn results in advantages with regard to the possibility of, in combination with other combustion- related parameters, such as, for example, ignition time, type of fuel/air mixture, the turbulence configuration in the cylinder, temperature, degree of supercharging, compression etc., refining the combustion process in order to achieve advantages with regard to the environment, fuel consumption, drivability in different situations etc. Further advantages and features of the invention emerge from the description and patent claims below.

The invention is explained in greater detail below by means of exemplary embodiments shown in the appended drawing .

Description of the figures In the drawing, Fig. 1 shows a diagrammatic view of a cylinder in an engine with an ignition electrode arrangement according to the invention,

Figs 2-4 show variants of the embodiment in Fig. 1, and Fig. 5 shows a section along V-V in Fig. 4.

Description of exemplary embodiments

Fig. 1 shows diagrammatically a cylinder 1 in an internal combustion engine, otherwise not shown in greater detail, with spark ignition, in this case of the Otto type. A piston 4 reciprocates in a cylinder block 2 which is covered at the top by a cylinder head 3. The cylinder 1 is provided with an ignition electrode arrangement 5 for igniting a fuel mixture introduced into the cylinder. Customary inlet and outlet valves in the cylinder, as well as other conventional components, have been omitted for the sake of simplicity and clarity, but do of course form part of the engine described. The ignition electrode arrangement 5 includes an ignition means 6 which is fastened removably in the cylinder head 3 and forms a first electrode 7 which interacts with a second electrode 8 which is in this case arranged on the piston 4. Here, the second electrode 8 has a laterally offset position on the piston 4, but it can of course have other positions, for example a centred position on the piston 4.

The first electrode 7 is arranged movably in the ignition means 6 and can, by means of an operating device 10 arranged on the ignition means 6, be displaced to and fro in the direction of the double arrow 11, essentially in the longitudinal direction of the cylinder. By virtue of the fact that the first electrode 7 is therefore movable relative to the cylinder head 3 and relative to the piston 4, it is possible to vary the size of the spark gap by means of the operating device 10 which, for the purpose, can suitably be controlled by a control unit 13 forming part of the ignition system of the vehicle in order in this way to vary the size of the spark gap as a function of suitable operating parameters, according to requirements. It is also possible to make the control unit 13 control the ignition voltage also as a function of suitable operating parameters, according to requirements, and in this manner to achieve further improved ignition control.

The single-pole ignition means 6 can consist of only a first electrode 7 which forms an insulated positive electrode, but it can, if appropriate, also consist of a combination of a positive electrode and a suitable fuel -injection means, which are assembled in such a manner that effective fuel injection can take place without the ignition function being jeopardized, and vice versa. In this connection, the second electrode 8 forms an earth electrode.

In the embodiment shown in Fig. 2, the second electrode 8 is arranged in a fixed manner on the ignition means 6 and is not therefore, in contrast to the embodiment in Fig. 1, movable relative to the cylinder head 3. On the other hand, the first electrode 7 is, as in the embodiment according to Fig. 1, movable relative to the cylinder head 3 according to the double arrow 11, by means of the operating member 10, for changing the size of the spark gap.

The embodiment according to Fig. 3 differs from the embodiment according to Fig. 2 only in that the second electrode 8 is in this case arranged in a fixed manner on the cylinder head 3 instead. Figs 4 and 5 show an embodiment in which the first electrode 7 is rotatable about its longitudinal axis, the direction of which essentially coincides with the longitudinal direction of the cylinder. By rotation in the direction of the double arrow 11, the distance between the two electrodes 7 and 8 can therefore be changed via the operating device 10 and the control unit 13, according to requirements. If required, it is possible to combine the rotation with an axial displacement as described above. In addition to the exemplary embodiments shown above, a number of other embodiments are of course possible within the scope of the invention, according to the requirements and prerequisites concerned. In the embodiments according to Figs 2-4, it is also possible, for example, to arrange a second electrode on the piston 4 also, in a similar manner to that in Fig. 1.

As shown, the invention can be applied to spark- ignited engines of the Otto type, but there is of course nothing to prevent the invention being applied instead to, for example, a two-stroke engine or another type of spark-ignited engine.

The adjustability of the size of the spark gap proposed according to the invention makes it possible in a suitable manner to change the spark gap as a function of the current operating situation, if appropriate in combination with control of the ignition voltage. In this way, a possibility is afforded for influencing the combustion in the cylinder advantageously' so that improvements are achieved with regard to, for example, fuel consumption, drivability and environmental aspects.

Claims

Patent Claims

1. Ignition electrode arrangement for a cylinder in an internal combustion engine, for example an Otto engine, in which a first electrode (7) and at least one second electrode (8) interact with one another, the first electrode (7) being arranged on an ignition means (6) fastened in a cylinder head (3) , characterized in that the first electrode (7) is arranged movably in the ignition means (6) and is in this way movable relative to the cylinder head (3) .

2. Ignition electrode arrangement according to Claim 1, characterized in that the first electrode (7) is movable essentially in the longitudinal direction of the cylinder.

3. Ignition electrode arrangement according to Claim 1, characterized in that the first electrode (7) is movable essentially in a plane at right angles to the longitudinal direction of the cylinder.

4. Ignition 'electrode arrangement according to any one of Claims 1-3, characterized in that a second electrode (8) is arranged on the cylinder head (3) .

5. Ignition electrode arrangement according to any one of Claims 1-3, characterized in that a second electrode (8) is arranged on the piston (4) of the cylinder.

6. Ignition electrode arrangement according to any one of Claims 1-3, characterized in that a second electrode (8) is arranged on the ignition means (6) .

7. Ignition electrode arrangement according to any one of Claims 1-6, characterized in that the first electrode (7) is positive.

8. Ignition electrode arrangement according to any one of Claims 1-7, characterized in that the first electrode (7) is connected to an operating device (10) by means of which it can be moved.

9. Ignition electrode arrangement according to Claim 8, characterized in that the operating device (10) is controlled by a control unit (13) forming part of the ignition system of the vehicle.

10. Ignition means for an ignition electrode arrangement for a cylinder in an internal combustion engine, provided with a first electrode (7) for interaction with a second electrode (8) , and arranged so as to be fastened in a cylinder head (3) , characterized in that the first electrode (7) is arranged movably.

11. Ignition means according ^' to Claim 10, characterized in that the ignition means bears an operating device (10) for operating the first electrode (7) .

12. Method for generating an ignition spark in an internal combustion engine, for example an Otto engine, in which an ignition spark is generated between a first electrode (7) on an ignition means (6) fastened in a cylinder head (3) and a second electrode (8) , characterized in that the position of the first electrode (7) relative to the second electrode (8) is varied during operation in order to change the size of the spark gap.

13. Method according to Claim 12, characterized in that the size of the spark gap is varied as a function of the current operating situation, on the basis of control information from a control unit (13) forming part of the ignition system of the vehicle.