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Title:
IGNITION METHOD AND SYSTEM OF AN INTERNAL COMBUSTION ENGINE PROVIDED WITH TWO SPARK PLUGS RESPECTIVELY COMPRISING ONE UNGROUNDED ELECTRODE
Document Type and Number:
WIPO Patent Application WO/2019/193253
Kind Code:
A1
Abstract:
A method and a system of igniting an internal combustion engine is described. According to the invention, at least one combustion chamber is provided that is arranged to receive at least two spark plugs having their electrodes in proximity to each other. In a work cycle of the engine are providing simultaneously by a pulsed ignition system at least two high voltage pulses of opposite polarity to the spark plugs, which brings the spark plugs to ignite a spark between their electrodes. In a subsequent work cycle of the engine the polarity of said high voltage pulses are reversed the spark plugs are brought to ignite a spark between their electrodes with the reversed polarity the pulses. The internal combustion engine is then run by igniting sparks between the spark plug electrodes and toggling the polarities of said electrodes according to a predetermined timing pattern.

Inventors:
JANHUNEN, Timo (Huopalahdentie 6 A9, Helsinki, 00330, FI)
Application Number:
FI2019/050267
Publication Date:
October 10, 2019
Filing Date:
April 02, 2019
Export Citation:
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Assignee:
JANHUNEN, Timo (Huopalahdentie 6 A9, Helsinki, 00330, FI)
International Classes:
F02P15/08; F02P15/02; F02B23/08; F02B75/02; F02B75/12; F02D41/38; F02P19/02; F23Q7/00
Foreign References:
DE10010753A12001-09-20
DE102012014037A12014-01-30
US20070209625A12007-09-13
DE3145169A11983-05-26
US2590778A1952-03-25
US6189522B12001-02-20
DE10010753A12001-09-20
Attorney, Agent or Firm:
SEPPO LAINE OY (Porkkalankatu 24, Helsinki, 00180, FI)
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Claims:
CLAIMS:

1. A method of igniting an internal combustion engine, the method comprising:

- providing at least one combustion chamber arranged to receive at least two spark plugs having their electrodes in proximity to each other;

- providing simultaneously in at least one work cycle of the engine by a pulsed ignition system at least two high voltage pulses of opposite polarity to said spark plugs;

- bringing said spark plugs to ignite a spark between their electrodes;

- reversing in a subsequent work cycle of the engine the polarity of said high voltage pulses and bringing said spark plugs to ignite a spark between their electrodes with said reversed polarity of said high voltage pulses;

- running said internal combustion engine by igniting sparks between said spark plug electrodes and toggling the polarities of said electrodes according to a predetermined timing pattern.

2. A method according to claim 1, wherein said high voltage pulses are generated to be at a positive voltage and a negative voltage compared to the potential at the body of the engine, and that their polarity is reversed by toggling the polarity of voltage pulses applied from a pulse generator circuit to the poles of a pair of ignition coils.

3. A method according to claim 1 or 2, wherein said predetermined timing pattern reverses the polarity of said high voltage pulses for each engine work cycle.

4. A method according to any of claims 1 - 3, wherein a series of sparks between said electrodes of said spark plugs is generated in at least some work cycles of the engine.

5. A method according to any of claims 1 - 4, wherein said combustion chamber is provided with a glow plug in the vicinity of said spark plugs.

6. A method according to claim 5, wherein said glow plug comprise pressure sensor.

7. A method according to any of claims 1 - 6, wherein the internal combustion engine is a two- stroke engine.

8. A method according to any of claims 1 - 6, wherein the internal combustion engine is a four- stroke engine.

9. An ignition system for an internal combustion engine, the system comprising:

- at least one combustion chamber arranged to receive at least two spark plugs with insulated electrodes arranged in said chamber;

- a high pulsed ignition system capable of providing simultaneously in at least one work cycle of the engine at least two high voltage pulses of opposite polarity to said spark plugs;

- said spark plugs being arranged in proximity to each other to ignite a spark between their electrodes upon receiving said high voltage pulses;

- said pulsed ignition system being capable in a subsequent work cycle of the engine to reverse the polarity of said high voltage pulses and bringing said spark plugs electrodes to ignite a spark between their electrodes with said reversed polarity of said high voltage pulses; and wherein

said internal combustion engine is run by igniting sparks between said spark plug electrodes and toggling the polarities of said electrodes according to a predetermined timing pattern. 10. A system according to claim 9, wherein said pulsed ignition system provides high voltage pulses of opposite polarity that are at a positive voltage and a negative voltage compared to the potential at the body of the engine, and that their polarity is reversed by toggling the polarity of voltage pulses applied from a pulse generator circuit to the poles of a pair of ignition coils.

11. A system according to claim 9 or 10, wherein said high voltage pulse system reverses the polarity of said high voltage pulses for each engine work cycle.

12. A system according to any of claims 9 - 11, wherein said ignition system generates a series of sparks between said electrodes of said spark plugs in at least some work cycles of the engine.

13. A system according to any of claims 9 - 12, wherein said combustion chamber is provided with a glow plug in the vicinity of said spark plugs. 14. A system according to claim 13, wherein said glow plug comprise pressure sensor.

15. A system according to any of claims 9 - 14, wherein the internal combustion engine is a two- stroke engine.

16. A system according to any of claims 9 - 14, wherein the internal combustion engine is a four-stroke engine.

17. A system according to any of claims 9 - 16, wherein said spark plugs are arranged to be received in a dome-like pre-chamber of said combustion chamber, wherein said spark plugs are oriented in order to have their electrodes in a close proximity to each other.

18. A system according to claim 17, wherein the electrodes of said spark plugs are arranged in a proximity to each other of about 0.5 mm.

Description:
IGNITION METHOD AND SYSTEM OF AN INTERNAL COMBUSTION ENGINE PROVIDED WITH TWO SPARK PLUGS RESPECTIVELY COMPRISING ONE

UNGROUNDED ELECTRODE

FIELD OF THE INVENTION

The present invention relates to a method and system of igniting an internal combustion engine.

BACKGROUND

The requirement of increased power output of internal combustion engines has led to the development of lean-bum engines, which allow a better efficiency than with stoichiometric combustion, in which the fuel and air is at a ratio of 14.7 parts of air to every one part of fuel. Benefits would include a decreased concentration of nitrogen oxides in the combustion process, and thus the atmosphere-warming carbon dioxide emissions are reduced.

The amount of additional air in lean-bum engines increases the engine compression in relation to the produced power when compared to stoichiometric combustion. The pressure in the cylinder may exceed 100 bar in some cases. This causes ignition problems, as lean mixtures are difficult to ignite and can cause potentially damaging ‘detonations’ where combustion is violently fast.

Most electronically controlled ignition systems use an npn transistor to control the ignition circuit which controls the firing of the spark plug. The transistor’s emitter is connected to ground and the collector to the negative pole of an ignition coil. When the ignition module of the engine provides a trigger signal to the base of the transistor, the transistor essentially short-circuits and conducts a current pulse to the ignition coil, which saturates. When the connection to ground is broken by the transistor going back to an off-state, the coil produces a high-voltage pulse to the spark plug.

In a lean-bum engine, the requirement of a high ignition voltage, as high as 50 to lOOkV or even more, can be a problem. Commercially available ignition coils can produce at most 50 to 60kV against zero, i.e. earth, due to e.g. insulation materials and need for space. The resistance to breakdown voltage of commercially available spark plugs is also limited to about 50 to 60kV against zero, i.e. earth. This is not necessarily sufficient to ignite the gas mixture in a lean-bum engine, as in high cylinder pressures the voltage is not sufficient to form a breakdown, i.e. a spark. There have been attempts to solve this problem with laser ignition and corona ignition, but so far there are no commercial applications for this.

In DE 10010753 is shown an arrangement with double ignition circuits for a cylinder, where two separate spark plugs are connected to opposite polarity voltages with a common ground. This allows the ignition voltage to be higher as the difference in potential between the spark plug electrodes is twice the voltage between one electrode and the ground, as in the case of a normal one-plug configuration with a grounded side electrode and an insulated central electrode. Thus it is possible to cause a spark breakdown between the central electrodes of the spark plugs in higher pressure than with a normal spark plug system, and to ignite a gas mixture in higher pressure than is possible with conventional method of coil plus spark plugs.

This would allow increasing the power of a spark-ignition internal combustion engine, especially a lean-bum engine.

In this prior art solution, although in principle solving the problem of providing higher ignition voltages, the erosion of the electrodes is one remaining issue. As the electrode connected to plus will get hotter than the electrode connected to minus, it will erode faster than the other one.

In view of the foregoing, it would be beneficial to provide an improved method and system for forming an ignition spark gap between the central electrodes of two spark plugs.

SUMMARY OF THE INVENTION The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

According to the invention, a spark breakdown between the central electrodes of two spark plugs may be achieved in a higher pressure than with normal spark plug systems, and thus to ignite a gas mixture at a higher pressure than what is possible with conventional coil-plus- spark plug arrangements with a side electrode. This allows increasing the power of an internal combustion engine, especially in the case of a lean-bum engine. The principle of using double ignition circuits providing opposite polarity voltages facilitates the switching of polarities between the ignition circuits and will offer some surprising beneficial effects. As the electrodes of the spark plugs are ignited with alternating polarity, the problem of electrode erosion is alleviated to a great extent. The electrodes of the spark plugs in the same cylinder will erode at the same pace, and the erosion will be slower.

Especially when the engine load is light, it may also be beneficial to fire a series of sparks during each cycle, which allowing the flame front to spread to a greater area of the combustion chamber for more efficient and consistent combustion. A series of sparks allow mixtures as lean as 23 : 1 , which means less fuel for the same power.

With conventional four-stroke engine systems, the ignition coil recharges during two engine revolutions for the next spark. However, in multi spark ignition systems the coils must be able to deliver all sparks in about one millisecond, which usually requires a high-energy system and specialized components. In the present invention, series of sparks can be generated.

According to an aspect of the present invention, there is provided a method of igniting an internal combustion engine, the method comprising the steps of: - providing at least one combustion chamber arranged to receive at least two spark plugs having their electrodes in proximity to each other;

- providing simultaneously in at least one work cycle of the engine by a pulsed ignition system at least two high voltage pulses of opposite polarity to said spark plugs;

- bringing said spark plugs to ignite a spark between their electrodes;

- reversing in a subsequent work cycle of the engine the polarity of said high voltage pulses and bringing said spark plugs to ignite a spark between their electrodes with said reversed polarity of said high voltage pulses;

- running said internal combustion engine by igniting sparks between said spark plug electrodes and toggling the polarities of said electrodes according to a predetermined timing pattern.

According to a second aspect of the invention an ignition system for an internal combustion engine is provided, the system comprising:

- at least one combustion chamber arranged to receive at least two spark plugs with insulated electrodes arranged in said chamber; - a high pulsed ignition system capable of providing simultaneously in at least one work cycle of the engine at least two high voltage pulses of opposite polarity to said spark plugs;

- said spark plugs being arranged in proximity to each other to ignite a spark between their electrodes upon receiving said high voltage pulses;

- said pulsed ignition system being capable in a subsequent work cycle of the engine to reverse the polarity of said high voltage pulses and bringing said spark plugs electrodes to ignite a spark between their electrodes with said reversed polarity of said high voltage pulses; and wherein

said internal combustion engine is run by igniting sparks between said spark plug electrodes and toggling the polarities of said electrodes according to a predetermined timing pattern.

Various embodiments of the first aspect may comprise at least one feature from the following bulleted list:

• the high voltage pulses are generated to be at a positive voltage and a negative voltage compared to the potential at the body of the engine, whereby their polarity is reversed by toggling the polarity of voltage pulses applied from a pulse generator circuit to the poles of a pair of ignition coils

• the predetermined timing pattern may reverse the polarity of said high voltage pulses for each engine work cycle

• a series of sparks between said electrodes of said spark plugs may be generated in at least some or every work cycle of the engine

• the combustion chamber may be provided with a glow plug in the vicinity of the spark plugs, and such a glow plug may comprise pressure sensor.

• the internal combustion engine is a two-stroke engine or a four-stroke engine.

• the spark plugs may be arranged to be received in a dome-like pre-chamber of the combustion chamber, wherein the spark plugs are oriented to have their electrodes in a close proximity to each other. The electrodes may be arranged in a proximity to each other of 0.5 mm, for example.

Considerable advantages are obtained by means of certain embodiments of the present invention. A portable material analyser is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates an engine ignition control system according to at least some embodiments of the present invention,

FIGURE 2 illustrates a schematic cross sectional view of a material analyser in accordance with at least some embodiments of the present invention, FIGURE 3 shows a pre-chamber arrangement that may be used in at least some embodiments of the present invention.

EMBODIMENTS

In Fig. 1, is presented an engine ignition control system according to at least some embodiments of the present invention. The central electrodes Sl and S2 of two spark plugs are altematingly connected a positive (+) and a negative (-) voltages in relation to their common zero potential, such as ± 50kV for example, thus doubling the voltage to 100 kV across the gap 11 between the electrodes Sl, S2, when the polarity of the spark plug electrodes are toggled in opposite directions.

An exemplary pulsed ignition system is formed by an engine management system 10, a power supply 12, a pulse generator circuit 13, and a pair of ignition coils Tl, T2 . The engine management system 10 receives ignition timing information from engine position and other sensors, as usually. The engine management system 10 is connected to a power supply 12 provided with transistors VI - V4, which may be IGBT power transistors, for example.

The power supply 12 charges a pulse generator circuit 13 consisting of switching semiconductors, such as thyristors V5 - V8 and their gate control transformers T3 and T4, and of capacitors Cl and C2 that discharges into the ignition coils Tl and T2, respectively, to generate the high-voltage pulses to the spark plug electrodes Sl and S2 that creates a spark between them.

The ignition coils Tl and T2 are at one pole connected together to form a common ground or zero voltage point 14 in relation to the body of the engine, and at the other pole connected to the central electrodes of spark plugs Sl, S2. Tl thus forms a first high-voltage connection configured for mounting to a first spark plug having an electrode Sl, and T2 forms a second high-voltage connection for coupling to the electrode S2 of a second spark plug, by means of high-voltage cables, for example. It is clear to one skilled in the art how to create pulses to ignition coils Tl and T2 and to generate voltages of, for example, 50 kV over each such coil. In Fig. 1 is thus shown one circuit as an enabling example. In a first engine cycle the pulse generator circuit 13 may thus generate a - 50 kV voltage in the ignition coil Tl and a + 50 kV voltage in the ignition coil T2. In the next engine ignition cycle the pulse generator circuit 13 may generate a + 50 kV voltage in the ignition coil Tl and a - 50 kV voltage in the ignition coil T2. In this manner, 50 kV pulses are thus produced by ignition coils Tl and T2 with reversed polarities according to a desired timing scheme. The timing scheme may call for reversed polarities for each engine cycle, or after n cycles, where n may be any integer. The timing scheme may also be altered by the engine management system 10, should external or internal conditions require.

The inventive engine ignition control system may also be configured to generate a series of sparks in a work cycle of the internal combustion engine, in order to further improve upon the ignition of the gas mixture in the combustion chamber of the engine.

Commercially available high-voltage coils can be used in connection with the present invention and commercially available spark plugs with removed or otherwise disabled side electrodes may be used.

The high ignition voltage that allows spark ignition in a higher compression pressure is especially suitable for use in so-called pre-chamber ignition systems. As shown in Fig. 2, the spark plugs 21, 22 are mounted in a pre-chamber 23 located outside the actual combustion chamber 20, so that their central electrodes may be positioned opposite each other within a spark gap distance G from each other, such as 0.5mm. The combustion chamber may be provided with a glow plug 27 or some other temperature adjustment arrangement in the pre- chamber EK or in the vicinity of the same, for adjusting the temperature of the chamber and to improve the ignition of the mixture therein. Inlet valves and exhaust valves 25 are also shown, as well as an injection port 26 with typical fuel injection patterns A, B, C and D.

The glow plug 27 may be equipped with a pressure sensor (not shown) in a similar manner as in diesel engines.

An exemplary pre-chamber arrangement is schematically shown in Fig. 3. A dome-shaped pre-chamber 30 is arranged in the cylinder head construction with two spark plugs 31 and 32, without side electrodes. The spark plugs 31, 32 are tilted and brought to such a proximity to each other that their insulated center electrodes 33, 34 are at a spark gap distance G from each other.

It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or“in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

The verbs“to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

At least some embodiments of the present invention find industrial application in the field of internal combustion engines.

CITATION LIST

Patent Literature DE 10010753