JP7756999B2 - internal combustion engine - Google Patents

Description

The present invention relates to a spark-ignition internal combustion engine.

In spark-ignition internal combustion engines, it has been considered to use a cap with an internal sub-chamber that houses the center electrode and ground electrode of the spark plug in order to optimize the combustion propagation speed (see, for example, Patent Document 1).

In the configuration described in Patent Document 1, after the air-fuel mixture is ignited in the auxiliary chamber, the combustion is propagated from the auxiliary chamber to another part of the combustion chamber (the main chamber) through a through hole provided in the cap.

JP 2014-159778 A

Most conventional internal combustion engines x1 of this type are port-injected, spark-ignition, four-stroke engines that inject fuel such as gasoline or hydrogen into an intake port (not shown) and introduce an air-fuel mixture into the combustion chamber. As shown in Figure 3, they at least include a cylinder head x4, an ignition plug x2, and a cap x3 located between the spark plug x2 and the cylinder head x4, which houses the center electrode x21 and ground electrode x22 of the spark plug x2 and has an auxiliary chamber x3s inside that communicates with the outside via multiple injection holes x3s1. Note that the spark plug x2 is shown uncut in Figure 3.

In this internal combustion engine x1, the air-fuel mixture is introduced from the main chamber x51 of the combustion chamber x5 to the auxiliary chamber x3s during the compression stroke. However, the injection hole x3s1, which connects the inside and outside of the auxiliary chamber x3s, has both the function of discharging burned gas from the auxiliary chamber to the outside and the function of introducing new air-fuel mixture from the outside into the auxiliary chamber. As a result, the introduction of new air-fuel mixture from the outside into the auxiliary chamber is hindered by residual burned gas, mainly in the upper part of the auxiliary chamber x3s, resulting in a problem of poor ignition performance.

The present invention was developed with the above points in mind, and aims to improve ignition performance in an internal combustion engine having a cap with an internal auxiliary chamber that houses at least the center electrode of the spark plug, by smoothly introducing new air-fuel mixture from the outside into the auxiliary chamber.

In order to solve the above-mentioned problems, the invention of claim 1 provides an internal combustion engine comprising an ignition plug attached to a cylinder head and having a center electrode, and a cap housing the center electrode of the spark plug and comprising an auxiliary chamber inside which communicates with the outside via a plurality of nozzle holes, wherein the nozzle holes are provided at the top and bottom of the auxiliary chamber, and a plate-like guide section is provided between the nozzle hole provided at the top of the auxiliary chamber and the nozzle hole provided at the bottom of the auxiliary chamber, protruding from a section of the cap adjacent and below the nozzle hole provided at the top towards the auxiliary chamber and sloping upward, and wherein the guide section is formed so as not to straddle a line connecting the tip of the center electrode of the spark plug to the upper nozzle hole, and also so as not to straddle a line connecting the tip of the center electrode of the spark plug to the lower nozzle hole .

In addition to the above-described configuration, the auxiliary chamber may have a plurality of injection holes in the upper portion thereof and a plurality of injection holes in the lower portion thereof .

According to the present invention, in an internal combustion engine having a cap with an internal auxiliary chamber that houses the center electrode and ground electrode of an ignition plug, the air-fuel mixture can be introduced through a nozzle hole below the guide portion, and burned gas can be discharged from a nozzle hole above the guide portion. Therefore, new air-fuel mixture can be smoothly introduced from the outside into the auxiliary chamber, improving ignition performance.

1 is a diagram showing a main part of an internal combustion engine according to an embodiment of the present invention; FIG. 4 is a diagram showing a main part of an internal combustion engine according to another embodiment of the present invention. FIG. 1 is a diagram showing a main part of a conventional internal combustion engine.

One embodiment of the present invention is described below with reference to Figure 1.

The internal combustion engine 1 according to this embodiment is a port-injection, spark-ignition, four-stroke engine that injects fuel such as gasoline or hydrogen into an intake port (not shown) and introduces an air-fuel mixture into the combustion chamber. As shown in FIG. 1, it is equipped with at least an ignition plug 2 and a cap 3 that is interposed between the spark plug 2 and the cylinder head 4, houses the center electrode 21 and ground electrode 22 of the spark plug 2, and has an auxiliary chamber 3s therein that communicates with the outside via a plurality of nozzle holes 3s1, 3s2. Note that the spark plug 2 is shown uncut in FIG. 1.

The spark plug 2 is a conventional type that is attached to the cylinder head 6 and has a center electrode 21 and a ground electrode 22. Although Figure 1 shows the entire spark plug 2 as a single unit, insulation is provided between the center electrode 21 and the ground electrode 22.

As mentioned above, the cap 3 is interposed between the spark plug 2 and the cylinder head 4. In this embodiment, the cap 3 is attached to the spark plug 2, and then the cap 3 and spark plug 2 are assembled to the cylinder head 4.

The cap 3 also has an auxiliary chamber 3s inside that houses the center electrode 21 and ground electrode 22 of the spark plug 2. This auxiliary chamber 3s is hemispherical and communicates with the outside, i.e., the main chamber 51 of the combustion chamber 5, via injection holes 3s1 and 3s2. In other words, as shown in Figure 1, the cap 3 has an auxiliary chamber 3s formed at its bottom that houses the center electrode 21 and ground electrode 22 and communicates with the main chamber 51 of the combustion chamber 5.

In this embodiment, an upper nozzle hole 3s1 is provided at the top of the auxiliary chamber 3s, a lower nozzle hole 3s2 is provided at the bottom of the auxiliary chamber 3s, and a guide portion 3g is provided midway between the upper nozzle hole 3s1 and the lower nozzle hole 3s2.

More specifically, multiple lower injection holes 3s2 are provided near the bottom of the cap 3, and multiple upper injection holes 3s1 are provided above the lower injection holes 3s2, more specifically in the upper half of the auxiliary chamber 3s. A plate-shaped guide portion 3g that slopes upward into the auxiliary chamber 3s projects from a portion adjacent to and below the upper injection holes 3s1. This guide portion 3g is formed so as not to straddle the lines connecting the tip of the center electrode 21 and each of the injection holes 3s1, 3s2, or the lines connecting the tip of the ground electrode 22 and each of the injection holes 3s1, 3s2.

In this embodiment, during the compression stroke, an air-fuel mixture is introduced into the auxiliary chamber 3s through the lower injection hole 3s2. The introduced air-fuel mixture flows along the guide portion 3g before being pushed to the top of the auxiliary chamber 3s. The burned gas remaining in the top of the auxiliary chamber 3s is pushed out by the introduced air-fuel mixture, flows along the guide portion 3g, and is then discharged from the auxiliary chamber 3s (main chamber 51) through the upper injection hole 3s1. That is, during the compression stroke, the air-fuel mixture flows from the lower injection hole 3s2 below the guide portion 3g before reaching the top of the auxiliary chamber 3s, and then flows from the top of the auxiliary chamber 3s above the guide portion 3g before flowing toward the upper injection hole 3s1.

As described above, when the air-fuel mixture is introduced into this auxiliary chamber 3s, a spark ignites it, and the ignited air-fuel mixture in the auxiliary chamber 3s is introduced into the main chamber 51 through the nozzle holes 3s1 and 3s2, where combustion propagates.

As described above, according to this embodiment, the upper injection hole 3s1 is located at what should be the top of the auxiliary chamber 3s, the lower injection hole 3s2 is located near the bottom of the cap 3, and the guide portion 3g is provided at a height between the upper injection hole 3s1 and the lower injection hole 3s2. As a result, as described above, the air-fuel mixture in the auxiliary chamber 3s flows from the lower injection hole 3s2 below the guide portion 3g and along said guide portion 3g before reaching the top of the auxiliary chamber 3s, and flows from the top of the auxiliary chamber 3s above the guide portion 3g and along said guide portion 3g before heading toward the upper injection hole 3s1. This makes it easier for new air-fuel mixture to be introduced smoothly from the outside to the inside of the auxiliary chamber 3s, improving ignition performance.

Note that the present invention is not limited to the embodiments described above.

For example, as shown in Figure 2, one possible configuration is to use a ground electrode to form the guide section.

The internal combustion engine A1 shown in Figure 2 is a port-injected, spark-ignition, four-stroke engine that injects fuel such as gasoline or hydrogen into an intake port (not shown) and introduces an air-fuel mixture into the combustion chamber. As shown in the figure, it is equipped with at least an ignition plug A2 and a cap A3 located between the ignition plug A2 and the cylinder head A4. The cap A3 houses the center electrode 21 of the ignition plug A2 and has an auxiliary chamber A3s therein that communicates with the outside, i.e., the main chamber A51 of the combustion chamber A5, via multiple injection holes A3s1 and A3s2. Note that the ignition plug A2 is shown uncut in Figure 2.

This type of spark plug A2 has a center electrode A21 but no ground electrode; instead, a ground electrode A31 is provided inside the cap A3.

In addition, in this embodiment, the ground electrode A31 functions as a guide. In other words, the cap A3 in this embodiment has multiple lower injection holes A3s2 near its bottom, and multiple upper injection holes A3s1 above the lower injection holes A3s2, more specifically in the upper half of the auxiliary chamber A3s. The ground electrode A31 protrudes into the auxiliary chamber A3s from a position adjacent to and below one of the upper injection holes A3s1, and a guide portion A3g protrudes into the auxiliary chamber A3s from a position adjacent to and below another of the upper injection holes A3s1.

In this configuration, too, the air-fuel mixture is introduced into the auxiliary chamber A3s through the lower injection hole A3s2 during the compression stroke. The introduced air-fuel mixture flows along the ground electrode A31 or guide portion A3g before being pushed to the top of the auxiliary chamber A3s. The burned gas remaining in the top of the auxiliary chamber A3s is pushed out by the introduced air-fuel mixture, flows along the ground electrode A31 or guide portion A3g, and is then discharged outside the auxiliary chamber A3s (main chamber A51) through the upper injection hole A3s1.

With this, the ground electrode on the spark plug A2 side can be omitted, reducing costs.

Furthermore, the shape of the auxiliary chamber is not limited to a hemisphere and can be set arbitrarily.

Furthermore, the guide portion may be formed in a ring shape along the inner wall of the auxiliary chamber.

In addition, the cap may be integral with the cylinder head or with the spark plug.

The position and number of the nozzle holes may also be set arbitrarily. However, if a guide portion (or a ground electrode functioning as a guide portion) is provided below and adjacent to the upper nozzle hole, as in the previously described embodiment, the guide portion can be used to effectively guide the burned residual gas to the upper nozzle hole, thereby effectively scavenging the residual gas.

Various other modifications may be made without departing from the spirit of the present invention.

1, A1...internal combustion engine 2, A2...spark plug 21, A21...center electrode 3, A3...cap 3s, A3s...auxiliary chamber 3s1, A3s1...nozzle hole (provided in the upper part of the auxiliary chamber) 3s2, A3s2...nozzle hole (provided in the lower part of the auxiliary chamber) 3g, A3g...guide portion A31...ground electrode

Claims (2)

a spark plug attached to the cylinder head and having a center electrode;
a cap that houses a center electrode of the ignition plug and has an auxiliary chamber therein that communicates with the outside through a plurality of injection holes,
the nozzle holes are provided at the upper and lower parts of the sub-chamber,
a plate-like guide portion that projects from a portion of the cap adjacent to and below the upper nozzle hole toward the interior of the auxiliary chamber and that is inclined upward is provided between the upper nozzle hole and the lower nozzle hole of the auxiliary chamber ,
The guide portion is formed so as not to straddle a line connecting the tip of the center electrode of the ignition plug and the nozzle hole provided in the upper part, and so as not to straddle a line connecting the tip of the center electrode of the ignition plug and the nozzle hole provided in the lower part . 2. An internal combustion engine according to claim 1 , wherein there are a plurality of injection holes in the upper part of said auxiliary combustion chamber and a plurality of injection holes in the lower part of said auxiliary combustion chamber .