JPS6139089Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ignition structure for a spark ignition engine. In spark ignition engines, locating the spark plug in the center of the combustion chamber shortens the combustion time per cycle, stabilizes combustion, and improves drivability and fuel efficiency. has traditionally been considered. However, if the spark plug is placed in the center of the combustion chamber, the spark plug will inevitably come close to the intake port, and the spark gap of the spark plug as well as the insulating material will be affected by the air-fuel mixture drawn into the combustion chamber from the intake port. exposed to the flow,
Therefore, a large amount of fuel droplets in the air-fuel mixture tend to adhere to the surface of the insulating member, and a decrease in insulation resistance due to carbon contamination of the ignition plug at low temperatures, so-called smoldering, is likely to occur.

By the way, in a normal engine, the air-fuel mixture that is drawn into the combustion chamber from the intake port passes through the annular space between the conical valve seat around the intake port and the umbrella of the intake valve, and then enters the combustion chamber. enter,
At this time, the spread of the air-fuel mixture spray is regulated by the conical surface of the valve seat, so that the main flow of the air-fuel mixture flows inside the virtual conical surface that includes the valve seat (towards the center of the engine combustion chamber).

The present invention focuses on the spread of the intake air mixture flow as described above, and by correcting the placement position of the spark plug according to this spread, even if the spark plug is placed in the center of the combustion chamber, the insulating member of the spark plug is An object of the present invention is to provide an ignition structure for an engine that prevents a spark plug from smoldering by making it difficult for fuel droplets in an air-fuel mixture to adhere to its surface.

According to the present invention, this purpose is to create a gas volume space between a rod-shaped center electrode, an insulating member that covers the center electrode except for its tip, and an insulating member that covers the insulating member and covers the center electrode. In an engine ignition structure in which a spark plug is installed in a plug hole and has a metal cylindrical housing with an outer electrode facing the center electrode,
The insulating member is located closer to the peripheral wall of the engine combustion chamber than a virtual conical surface including a conical valve seat around the intake port, and the center electrode and the outer electrode are located closer to the center of the engine combustion chamber than the virtual conical surface. This is achieved by an engine ignition structure characterized in that it is configured such that a spark gap formed between the two is located.

According to this configuration, since the insulating member is located closer to the peripheral wall of the engine combustion chamber than the virtual conical surface, the insulating member is directly exposed to the spray stream of the air-fuel mixture sucked into the engine combustion chamber from the intake port. This reduces the amount of droplet fuel in the air-fuel mixture that adheres to the surface of the insulating member, thereby preventing or reducing the deposition of carbon particles on the surface.

Even if the insulating member is located closer to the peripheral wall of the engine combustion chamber than the virtual conical surface, the spark gap is located closer to the center of the engine combustion chamber than the virtual conical surface, and is injected into the spray stream of the air-fuel mixture drawn into the engine combustion chamber from the intake port. Since it is directly exposed, the discharge electrode is cooled well, and the spark gap is located at the center of the engine combustion chamber, away from the wall of the engine combustion chamber, improving ignition performance and shortening the combustion time. , drivability and lean limit are improved.

It is preferable that the spark plug used in the ignition structure according to the present invention has a center electrode that has a large protrusion length beyond the insulating member, and is configured such that the spark gap is formed at a position sufficiently distant from the insulating member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic longitudinal sectional view showing the main parts of an embodiment of an engine equipped with an ignition structure according to the present invention. In the figure, reference numeral 1 designates a cylinder block, which receives a piston 3 in its cylinder bore 2 in a slidable manner. A cylinder head 5 is attached to the upper part of the cylinder block 1 via a gasket 4. The cylinder head 5 has a wedge-shaped combustion chamber recess 6 aligned with the cylinder bore 2, and cooperates with the cylinder block 1 and piston 3 to define a combustion chamber 7.

The cylinder head 5 is provided with an intake port 8 that opens into the combustion chamber 7 at one end.
An annular valve seat member 9 is attached to the open end of the intake port 8. The valve seat member 9 has a valve seat 10 having a conical surface. Also, the cylinder head 5 has a guide sleeve 1.
An intake valve 12 is attached via 1.
The conical sealing surface 13 of the intake valve 12 engages with the valve seat 10 by a well-known valve operating device (not shown), thereby opening the intake port 8.
When the valve is closed, the sealing surface 13 is away from the valve seat 10 and the intake port 8 is closed, as shown in the figure.
The valve is driven between the open position and the open position.

A plug hole 14 is formed in the cylinder head 5, and the plug hole 14 opens into the combustion chamber 7 at one end and opens into the outer wall of the cylinder head at the other end. This plug hole 14
is configured as a screw hole.

15 indicates a spark plug. spark plug 1
5 includes a rod-shaped center electrode 16, an insulating member 17 such as an insulator that covers the center electrode 16 except for its tip, and a gas volume space 18 that covers the insulating member 17 and creates a gas volume space 18 between the insulating member and the insulating member. It has a metal cylindrical housing 20 having a defined outer electrode 19 facing the center electrode 16. A portion of the outer periphery of the cylindrical housing 20 is a threaded portion, and the spark plug 15 is screwed into the plug hole 14 using this threaded portion and fixed to the cylinder head 5. As shown, spark plug 1
5 is screwed into the plug hole 14 and in the normal installed state, the insulating member 17 is located closer to the peripheral wall of the combustion chamber than the imaginary conical surface (indicated by imaginary lines in the figure) including the valve seat 10, Center electrode 16
The spark gap 21 formed between the outer electrode 19 and the outer electrode 19 is located closer to the center of the combustion chamber than the virtual conical surface. In such an embodiment:
The protrusion length l of the center electrode 16 is longer than that of a conventional general spark plug, and the spark gap 2
1 is arranged as close to the center of the combustion chamber 7 as possible. This protrusion length l is preferably 1 mm or more.

As mentioned above, the insulating member 17 is connected to the valve seat 10.
Since it is located closer to the combustion chamber circumferential wall than the virtual conical surface containing the
As a result, the amount of droplet fuel in the mixture that adheres to the surface of the insulating member 17 is reduced, and the carbon of the spark plug caused by the adhering fuel decreases. Contamination is reduced. Further, since the spark gap 21 is located closer to the center of the combustion chamber than the virtual conical surface and is directly exposed to the spray flow of the air-fuel mixture taken into the combustion chamber 7 from the intake port 8, the center electrode 16 and the outer electrode 19 are cooled by the air-fuel mixture, and these are prevented from becoming overheated. Also spark gap 2
1 is located further away from the combustion chamber wall and closer to the center of the combustion chamber, improving ignition performance, shortening combustion time, and improving driveability and lean mixture limit.

FIG. 2 is a schematic vertical sectional view showing the main parts of another embodiment of the engine equipped with the ignition structure according to the present invention. In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals as in FIG. This embodiment has substantially the same construction as the embodiment described above, except that the combustion chamber recess 6 is formed as a hemispherical combustion chamber recess. That is, even in such embodiments,
The insulating member 17 of the spark plug 15 is connected to the valve seat 1
The spark gap 21 is located closer to the peripheral wall of the engine combustion chamber than the virtual conical surface including 0, and the spark gap 21 is located closer to the center of the engine combustion chamber than the virtual conical surface.

FIG. 3 shows the relationship between the position of the insulating member of the spark plug with respect to the virtual conical surface and the insulation resistance value of the spark plug. This graph shows the results of preparing multiple engines of the same type with spark plugs located at different positions with respect to the virtual conical surface, operating them under the same warm-up pattern under the same conditions, and then It is obtained by measuring the insulation resistance value of each engine's spark plug. As is clear from this graph, if the insulating member of the spark plug is located closer to the center of the engine combustion chamber than the virtual conical surface,
The insulation resistance value is low, which is not preferable, but the closer the insulation member is to the peripheral wall of the engine combustion chamber than the virtual conical surface, the higher the insulation resistance value is, which is preferable.

Therefore, it will be understood that the same effects as the above-mentioned embodiment can be obtained in this embodiment as well.

In the above, the present invention has been described in detail with reference to specific embodiments, but it will be appreciated by those skilled in the art that the present invention is not limited to these embodiments, and that various embodiments are possible within the scope of the present invention. It should be obvious.

[Brief explanation of drawings]

1 and 2 are schematic longitudinal sectional views showing the main parts of an embodiment of an engine equipped with an ignition structure according to the present invention, and FIG. 3 shows the position of the insulating member of the ignition plug and the insulation resistance value of the ignition plug. It is a graph showing the relationship between. 1... Cylinder block, 2... Cylinder bore, 3... Piston, 4... Gasket, 5...
Cylinder head, 6... Combustion chamber recess, 7... Combustion chamber, 8... Intake port, 9... Valve seat member, 10... Valve seat, 11... Guide sleeve, 12... Intake valve, 13... Seal surface,
14...Plug hole, 15...Spark plug, 1
6... Center electrode, 17... Insulating member, 18... Gas volume space, 19... Outer electrode, 20...
Cylindrical housing, 21...spark gap.

Claims (1)

[Scope of utility model registration request] 1. An ignition structure for an engine in which an ignition plug is attached to a plug hole, the ignition plug having a rod-shaped center electrode, an insulating member covering the periphery of the center electrode except for the tip, and a metallic cylindrical housing covering the periphery of the insulating member and defining a gas volume space between the insulating member and an outer electrode facing the center electrode, wherein the insulating member is located on the peripheral wall side of the engine combustion chamber from an imaginary conical surface including a conical valve seat around an intake port, and a spark gap formed between the center electrode and the outer electrode is located on the central side of the engine combustion chamber from the imaginary conical surface.