Multipoint ignition engine

Abstract

A multipoint ignition engine (1) includes a central electrode pair (9), disposed in the center of a combustion chamber (2), for forming a central spark gap (10), and a plurality of peripheral electrode pairs (12) held in a head gasket (15), which has an opening portion having a substantially identical diameter to an opening portion of a cylinder (5) in a position corresponding to the opening portion of the cylinder (5), for forming a plurality of peripheral spark gaps (13) around the inner periphery of the opening portion in the cylinder (5). An air-fuel mixture in the combustion chamber (2), which is obtained by mixing together fuel and air evenly to the stoichiometric air-fuel ratio or a richer/leaner air-fuel ratio than the stoichiometric air-fuel ratio, is ignited using both the central spark gap (10) and the plurality of peripheral spark gaps (13).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a multipoint ignition engine according to this invention.

FIG. 2 is a view showing the structure of a head gasket.

FIG. 3 is a view showing the relationship between a number of peripheral spark gaps and a gap width at which a spark can be generated with stability.

FIG. 4 is a view illustrating a method of manufacturing the head gasket.

FIG. 5 is a view showing a state of flame propagation through the interior of a combustion chamber.

FIG. 6 is a view showing the relationship between the number of peripheral spark gaps and an upper limit of an excess air ratio (a lean limit).

FIG. 7 is a view showing a second embodiment of this invention.

FIG. 8 is also a view of the second embodiment of this invention, showing an upper surface of a piston.

FIG. 9 is a view showing a partially modified example of the second embodiment of this invention.

FIG. 10 is a view of the same partially modified example of the second embodiment of this invention, showing the upper surface of the piston.

FIG. 11 is a view showing a third embodiment of this invention.

FIG. 12 is a view showing a fourth embodiment of this invention.

FIG. 13 is a view showing a fifth embodiment of this invention.

FIG. 14 is a view showing a sixth embodiment of this invention.

FIG. 15 is a view showing a seventh embodiment of this invention.

FIG. 16 is a XVI-XVI sectional view of FIG. 15.

FIG. 17 is a view showing a partially modified example of the seventh embodiment of this invention.

FIG. 18 is a XVIII-XVIII sectional view of FIG. 17.

FIG. 19 is a XIX-XIX sectional view of FIG. 15.

FIG. 20 is a view showing a partially modified example of the seventh embodiment of this invention.

FIG. 21 is a view showing a partially modified example of the seventh embodiment of this invention.

FIG. 22 is a view showing an eighth embodiment of this invention.

FIG. 23 is a view showing a partially modified example of the eighth embodiment of this invention.

FIG. 24 is a view showing a ninth embodiment of this invention.

FIG. 25 is also a view of the ninth embodiment of this invention, showing the structure of a power-receiving pin of an ignition ring.

Claims

1. A multipoint ignition engine, comprising: a cylinder head having a combustion chamber formed on a bottom surface thereof;a cylinder block having a cylinder in a position opposing the combustion chamber;a piston accommodated in the cylinder;a central electrode pair, disposed in a center of the combustion chamber, for forming a central spark gap; anda plurality of peripheral electrode pairs held in an insulating member, which has an opening portion having a substantially equal diameter to an opening portion of the cylinder in a position corresponding to the opening portion in the cylinder, for forming a plurality of peripheral spark gaps around an inner periphery of the opening portion in the cylinder,wherein an air-fuel mixture in the combustion chamber, which is obtained by mixing together fuel and air evenly, is ignited using both the central spark gap and the plurality of peripheral spark gaps.

2. The multipoint ignition engine as defined in claim 1, wherein the multipoint ignition engine is a premix engine that generates a homogeneous air-fuel mixture by mixing fuel that is injected into an intake port with air, and introduces the air-fuel mixture into the combustion chamber.

3. The multipoint ignition engine as defined in claim 1, wherein the multipoint ignition engine is a direct injection engine that generates a homogeneous air-fuel mixture in the combustion chamber by injecting fuel into the combustion chamber during an intake stroke.

4. The multipoint ignition engine as defined in claim 1, wherein a phase difference is provided between a voltage application timing relating to the plurality of peripheral spark gaps and a voltage application timing relating to the central spark gap.

5. The multipoint ignition engine as defined in claim 4, wherein the voltage application timing relating to the plurality of peripheral spark gaps is later than the voltage application timing relating to the central spark gap.

6. The multipoint ignition engine as defined in claim 1, wherein the plurality of peripheral spark gaps are disposed at equal circumferential direction intervals around the inner periphery of the opening portion in the cylinder.

7. The multipoint ignition engine as defined in claim 1, wherein all of the plurality of peripheral electrode pairs are electrically connected in series by conductive members, and a voltage application device is provided for applying a voltage to one end of the serially connected plurality of peripheral electrode pairs.

8. The multipoint ignition engine as defined in claim 7, further comprising: a power-receiving member connected electrically to one end of the serially connected plurality of peripheral electrode pairs; anda rod-form member inserted into a through hole so as to contact the power-receiving member, the through hole extending from an outside surface of the cylinder head or the cylinder block to the power-receiving member;wherein the voltage application device supplies the voltage from the voltage application device to the plurality of peripheral electrode pairs via the rod-form member.

9. The multipoint ignition engine as defined in claim 7, wherein the plurality of peripheral electrode pairs and the conductive members are formed from different materials.

10. The multipoint ignition engine as defined in claim 9, wherein a heat value of an ignition device comprising the plurality of peripheral electrode pairs is adjusted by modifying at least one of a length, a thickness, a width, and a material of the conductive members.

11. The multipoint ignition engine as defined in claim 1, wherein the plurality of peripheral electrode pairs are divided into a plurality of groups, the plurality of peripheral electrode pairs in each of the groups are electrically connected in series by conductive members, anda voltage application device is provided for applying a voltage to one end of the serially connected plurality of peripheral electrode pairs in each of the groups.

12. The multipoint ignition engine as defined in claim 11, further comprising: a power-receiving member connected electrically to one end of the serially connected plurality of peripheral electrode pairs; anda rod-form member inserted into a through hole so as to contact the power-receiving member, the through hole extending from an outside surface of the cylinder head or the cylinder block to the power-receiving member;wherein the voltage application device supplies the voltage from the voltage application device to the plurality of peripheral electrode pairs via the rod-form member.

13. The multipoint ignition engine as defined in claim 11, wherein the plurality of peripheral electrode pairs and the conductive members are formed from different materials.

14. The multipoint ignition engine as defined in claim 13, wherein a heat value of an ignition device comprising the plurality of peripheral electrode pairs is adjusted by modifying at least one of a length, a thickness, a width, and a material of the conductive members.

15. The multipoint ignition engine as defined in claim 1, wherein the insulating member is a head gasket sandwiched between the cylinder head and the cylinder block.

16. The multipoint ignition engine as defined in claim 15, wherein the insulating member is formed by bonding together two plates made of an insulating material, and a base portion of each of the plurality of peripheral electrode pairs is accommodated and held in a recessed groove formed in at least one of the two plates.

17. The multipoint ignition engine as defined in claim 1, wherein a counter bore portion is formed in at least one of the cylinder head and the cylinder block in a position corresponding to the opening portion in the cylinder, and the insulating member is an annular member accommodated in the counter bore portion.

18. The multipoint ignition engine as defined in claim 17, wherein the insulating member is formed by bonding together two plates made of an insulating material, and a base portion of each of the plurality of peripheral electrode pairs is accommodated and held in a recessed groove formed in at least one of the two plates.

19. The multipoint ignition engine as defined in claim 1, wherein a radius of a circle passing through the plurality of peripheral spark gaps is equal to a radius of the opening portion in the cylinder.

20. The multipoint ignition engine as defined in claim 19, wherein a top dead center position of the piston is set in a higher position than the peripheral spark gap.

21. The multipoint ignition engine as defined in claim 19, wherein a tip end surface of the peripheral electrode pair is flush with an inner peripheral surface of the opening portion in the insulating member.

22. The multipoint ignition engine as defined in claim 19, wherein recessed portions are formed in the inner peripheral surface of the opening portion in the insulating member in positions respectively facing the plurality of peripheral spark gaps, and the plurality of peripheral spark gaps are exposed from the respectively corresponding recessed portions.

23. The multipoint ignition engine as defined in claim 1, wherein a radius of a circle passing through the plurality of peripheral spark gaps is smaller than a radius of the cylinder.

24. The multipoint ignition engine as defined in claim 23, wherein at least a part of the plurality of peripheral electrode pairs that protrudes into the combustion chamber takes a linear rod form, and the peripheral spark gap is formed by causing an end surface of one of the electrodes constituting the peripheral electrode pair to face a side face of the other electrode with a gap therebetween.

25. The multipoint ignition engine as defined in claim 23, wherein the plurality of peripheral electrode pairs are constituted by S-shaped electrodes, and the peripheral spark gap is formed by causing tip ends of the electrodes constituting the peripheral electrode pair to face each other.

26. The multipoint ignition engine as defined in claim 23, wherein a part of the insulating member that holds the plurality of peripheral electrode pairs protrudes into an inner side of the combustion chamber.

27. The multipoint ignition engine as defined in claim 1, wherein leakage-preventing indentations are formed in a crown surface of the piston in positions corresponding to respective circumferential direction positions of the plurality of peripheral spark gaps.

28. The multipoint ignition engine as defined in claim 27, wherein a length of the leakage-preventing indentation in a radial direction of the cylinder is greater than a length thereof in a circumferential direction of the cylinder.

29. The multipoint ignition engine as defined in claim 1, wherein leakage-preventing indentations are formed in the cylinder head in positions corresponding to the respective circumferential direction positions of the plurality of peripheral spark gaps.

30. The multipoint ignition engine as defined in claim 29, wherein a length of the leakage-preventing indentation in a radial direction of the cylinder is greater than a length thereof in a circumferential direction of the cylinder.